Abdominal lift for laparoscopic cholecystectomy

  • Conclusions changed
  • Review
  • Intervention

Authors


Abstract

Background

Laparoscopic cholecystectomy (key-hole removal of the gallbladder) is now the most often used method for treatment of symptomatic gallstones. Several cardiopulmonary changes (decreased cardiac output, pulmonary compliance, and increased peak airway pressure) occur during pneumoperitoneum, which is now introduced to allow laparoscopic cholecystectomy. These cardiopulmonary changes may not be tolerated in individuals with poor cardiopulmonary reserve.

Objectives

To assess the benefits and harms of abdominal wall lift compared to pneumoperitoneum in patients undergoing laparoscopic cholecystectomy.

Search methods

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until February 2013.

Selection criteria

We included all randomised clinical trials comparing abdominal wall lift (with or without pneumoperitoneum) versus pneumoperitoneum.

Data collection and analysis

We calculated the risk ratio (RR), rate ratio (RaR), or mean difference (MD) with 95% confidence intervals (CI) based on intention-to-treat analysis with both the fixed-effect and the random-effects models using the Review Manager (RevMan) software.

Main results

For abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, a total of 130 participants (all with low anaesthetic risk) scheduled for elective laparoscopic cholecystectomy were randomised in five trials to abdominal wall lift with pneumoperitoneum (n = 53) versus pneumoperitoneum only (n = 52). One trial which included 25 people did not state the number of participants in each group. All five trials had a high risk of bias. There was no mortality or conversion to open cholecystectomy in any of the participants in the trials that reported these outcomes. There was no significant difference in the rate of serious adverse events between the two groups (two trials; 2/29 events (0.069 events per person) versus 2/29 events (0.069 events per person); rate ratio 1.00; 95% CI 0.17 to 5.77). None of the trials reported quality of life, the proportion of people discharged as day-patient laparoscopic cholecystectomies, or pain between four and eight hours after the operation. There was no significant difference in the operating time between the two groups (four trials; 53 participants versus 54 participants; 13.39 minutes longer (95% CI 2.73 less to 29.51 minutes longer) in the abdominal wall lift with pneumoperitoneum group and 100 minutes in the pneumoperitoneum group).

For abdominal wall lift versus pneumoperitoneum, a total of 774 participants (the majority with low anaesthetic risk) scheduled for elective laparoscopic cholecystectomy were randomised in 18 trials to abdominal wall lift without pneumoperitoneum (n = 332) versus pneumoperitoneum (n = 358). One trial which included 84 people did not state the number in each group. All the trials had a high risk of bias. There was no mortality in any of the trials that reported this outcome. There was no significant difference in the proportion of participants with serious adverse events (six trials; 5/172 (weighted proportion 2.4%) versus 2/171 (1.2%); RR 2.01; 95% CI 0.52 to 7.80). There was no significant difference in the rate of serious adverse events between the two groups (three trials; 5/99 events (weighted number of events per person = 0.346 events) versus 2/99 events (0.020 events per person); rate ratio 1.73; 95% CI 0.35 to 8.61). None of the trials reported quality of life or pain between four and eight hours after the operation. There was no significant difference in the proportion of people who underwent conversion to open cholecystectomy (11 trials; 5/225 (weighted proportion 2.3%) versus 7/235 (3.0%); RR 0.76; 95% CI 0.26 to 2.21). The operating time was significantly longer in the abdominal wall lift group than in the pneumoperitoneum group (16 trials; 6.87 minutes longer (95% CI 4.74 minutes to 9.00 minutes longer) in the abdominal wall lift group versus 75 minutes in the pneumoperitoneum group). There was no significant difference in the proportion of people discharged as laparoscopic cholecystectomy day-patients (two trials; 15/31 (weighted proportion 48.5%) versus 9/31 (29%); RR 1.67; 95% CI 0.85 to 3.26).

Authors' conclusions

Abdominal wall lift with or without pneumoperitoneum does not seem to offer an advantage over pneumoperitoneum in any of the patient-oriented outcomes for laparoscopic cholecystectomy in people with low anaesthetic risk. Hence it cannot be recommended routinely. The safety of abdominal wall lift is yet to be established. More research on the topic is needed because of the risk of bias in the included trials and because of the risk of type I and type II random errors due to the few participants included in the trials. Future trials should include people at higher anaesthetic risk. Furthermore, such trials should include blinded assessment of outcomes.

Plain language summary

Abdominal wall lift for people undergoing gallbladder removal by a key-hole operation

Key-hole removal of the gallbladder (laparoscopic cholecystectomy) is currently the preferred treatment for people with symptoms related to gallstones in the gallbladder. This is generally performed by distending the tummy (abdomen) using carbon dioxide gas (pneumoperitoneum) so that there is adequate space for instruments and to visualise the structures within the abdomen. This enables the surgeons to identify and divide the appropriate structures. However, distending the abdominal wall can result in various physiological changes that affect the functioning of the heart or lungs. These changes are more pronounced at higher pressures of the gas used to distend the abdomen. They are generally tolerated well in people with a low risk of anaesthetic problems. However, those with pre-existing illnesses may not tolerate this distension of the abdomen well. So, an alternate method of enabling the surgeons to visualise the structures in the abdomen and to use instruments by lifting up the abdominal wall using special devices (abdominal wall lift) has been suggested for people undergoing laparoscopic cholecystectomy. We reviewed all the relevant information from randomised trials (a type of study which provides the best information on whether one treatment is better than the other, if conducted properly) in the literature to find out if abdominal wall lift is better than distending the abdomen using carbon dioxide gas. We adopted methods to identify all the possible studies and used methods that decrease the errors in data collection.

Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum
A total of 130 participants (all with low anaesthetic risk) were included in five trials which compared abdominal wall lift combined with very low pressure pneumoperitoneum and standard pneumoperitoneum. All five trials had a high risk of bias (introducing the possibility of overestimating benefits or underestimating the harms of abdominal wall lift). No-one died as a result of surgery. There was no significant difference in the rate of serious complications related to the surgery. None of the trials reported quality of life, the proportion of people discharged as laparoscopic cholecystectomy day-patients, or pain between four and eight hours after the operation. None required conversion of key-hole surgery to an open operation using a larger incision. There was no significant difference in the operating time between the two groups.

Abdominal wall lift versus pneumoperitoneum
A total of 774 participants (the majority with low anaesthetic risk) who underwent planned laparoscopic cholecystectomy were included in 18 trials which compared abdominal wall lift and standard pneumoperitoneum. All the trials had a high risk of bias. No-one died as a result of the surgery. There was no significant difference in the rate of serious complications related to surgery. None of the trials reported quality of life or pain between four and eight hours after the operation. There was no significant difference in the rate of serious adverse events, the proportion of people who underwent an open operation using a larger incision, or the proportion discharged on the same day of surgery. The operating time was about seven minutes longer on average if the operation was performed using abdominal wall lift rather than pneumoperitoneum.

In summary, abdominal wall lift does not seem to offer an advantage over pneumoperitoneum in any of the patient-oriented outcomes for laparoscopic cholecystectomy in people with low anaesthetic risk. Abdominal wall lift may increase costs by increasing the operating time. Hence it cannot be recommended routinely. The safety of abdominal wall lift is yet to be established. More randomised clinical trials on the topic are needed since the possibility of arriving at erroneous conclusions due to bias and due to the play of chance was high because of the design of the trials. Future trials should include people at high risk during anaesthesia. Furthermore, such trials should employ blinded assessments of outcome measures.

Summary of findings(Explanation)

Summary of findings for the main comparison. Abdominal lift for laparoscopic cholecystectomy
  1. 1 High risk of bias.
    2 The confidence interval overlaps 1 and either/or 0.75 and 1.25.
    3 There were fewer than 300 events in both groups.
    4 Because of the few trials, we were unable to assess publication bias by funnel plot. However, this outcome was reported only in a small proportion of trials suggesting that there is evidence of selective reporting.
    5 The results were different in the fixed-effect and random-effects model.

Abdominal lift with pneumoperitoneum versus pneumoperitoneum for laparoscopic cholecystectomy
Patient or population: patients undergoing laparoscopic cholecystectomy.
Settings: secondary and tertiary care.
Intervention: abdominal lift with pneumoperitoneum versus pneumoperitoneum.
OutcomesIllustrative comparative risks* (95% CI)Relative effect
(95% CI)
No of participants
(studies)
Quality of the evidence
(GRADE)
Comments
Assumed riskCorresponding risk
Pneumoperitoneum Abdominal lift with pneumoperitoneum
Serious adverse events 69 per 1000 69 per 1000
(12 to 398)
Rate ratio 1
(0.17 to 5.77)
58
(2 studies)
⊕⊝⊝⊝
very low 1,2,3,4
 
Operating timeThe mean operating time in the control groups was 100
minutes
The mean operating time in the intervention groups was
13.39 higher
(2.73 lower to 29.51 higher)
 107
(4 studies)
⊕⊝⊝⊝
very low 1,5
 
*The basis for the assumed risk is the mean control group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval.
GRADE Working Group grades of evidence
High quality: further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: we are very uncertain about the estimate.

Summary of findings 2 Abdominal lift for laparoscopic cholecystectomy

Summary of findings 2. Abdominal lift for laparoscopic cholecystectomy
  1. 1 High risk of bias.
    2 The confidence interval overlaps 1 and either 0.75 or 1.25.
    3 There were fewer than 300 events in both groups.
    4 Because of the few trials, we were unable to assess publication bias by funnel plot. However, this outcome was reported only in a small proportion of trials suggesting that there is evidence of selective reporting.
    5 There was significant heterogeneity.

Abdominal wall lift versus pneumoperitoneum for laparoscopic cholecystectomy
Patient or population: patients with laparoscopic cholecystectomy.
Settings: secondary or tertiary setting.
Intervention: abdominal wall lift versus pneumoperitoneum.
OutcomesIllustrative comparative risks* (95% CI)Relative effect
(95% CI)
No of participants
(studies)
Quality of the evidence
(GRADE)
Assumed riskCorresponding risk
Pneumoperitoneum Abdominal wall lift
Serious adverse events (number of serious adverse events) 20 per 1000 34.6 per 1000
(7 to 172)
Rate ratio 1.73
(0.35 to 8.61)
198
(3 studies)
⊕⊝⊝⊝
very low 1,2,3,4
Serious adverse events (proportion of patients with serious adverse events) 12 per 1000 24 per 1000
(6 to 91)
RR 2.01
(0.52 to 7.80)
343
(6 studies)
⊕⊝⊝⊝
very low 1,2,3,4
Conversion to open cholecystectomy 30 per 1000 23 per 1000
(8 to 66)
RR 0.76
(0.26 to 2.21)
460
(11 studies)
⊕⊝⊝⊝
very low 1,2,3,4
Operating timeThe mean operating time in the control groups was 75 minutesThe mean operating time in the intervention groups was
6.87 higher
(4.74 to 9.00 higher)
 649
(16 studies)
⊕⊝⊝⊝
very low 1,5
Proportion discharged as day-patient laparoscopic cholecystectomy 290 per 1000 485 per 1000
(247 to 946)
RR 1.67
(0.85 to 3.26)
62
(2 studies)
⊕⊝⊝⊝
very low 1,2,3,4
*The basis for the assumed risk is the mean control group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval; RR: Risk ratio.
GRADE Working Group grades of evidence
High quality: further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: we are very uncertain about the estimate.

Background

About 10% to 15% of the adult western population have gallstones (Jørgensen 1987; NIH 1992; Muhrbeck 1995; Halldestam 2004). Between 1% and 4% become symptomatic in a year (NIH 1992; Halldestam 2004). More than half a million cholecystectomies (removal of the gallbladder) are performed per year in the United States alone (NIH 1992). Regional differences exist in the cholecystectomy rates (Mjäland 1998). Laparoscopic (key-hole) cholecystectomy is now the preferred method of cholecystectomy (NIH 1992; Fullarton 1994; Bakken 2004; Keus 2006).

Traditionally, one of the first steps in laparoscopic cholecystectomy is the creation of pneumoperitoneum (Russell 1993) using carbon dioxide (CO₂) applied through a Veress needle (Andersson 2003) or through a port (hole) (Galizia 2001; Alijani 2004) in the abdominal wall. The created pneumoperitoneum helps in the visualisation and manipulation of instruments inside the abdominal cavity. However, the increased intra-abdominal pressure due to the pneumoperitoneum causes several cardiopulmonary changes. The increased intra-abdominal pressure also increases the absorption of CO₂ (causing hypercapnia and acidosis), which has to be avoided by hyperventilation (Henny 2005). The increased intra-abdominal pressure pushes the diaphragm upwards decreasing the pulmonary compliance (Alijani 2004; Henny 2005) and increasing the peak airway pressure (Galizia 2001; Alijani 2004). Pneumoperitoneum also increases the systemic vascular resistance (Galizia 2001; Mertens 2004) and pulmonary vascular resistance (Galizia 2001). CO₂ pneumoperitoneum predisposes the patient to cardiac arrhythmias (Egawa 2006). During the early phase of pneumoperitoneum, there is a decrease in heart rate (Alijani 2004) and a reduction in cardiac output (Galizia 2001; Alijani 2004) as a result of decreased venous return (Neudecker 2002). While these cardiopulmonary changes may be tolerated by healthy adults with adequate cardiopulmonary reserve, people with cardiopulmonary disease may not tolerate these cardiopulmonary changes well. About 17% of patients undergoing laparoscopic cholecystectomy have an American Society of Anesthesiologists (ASA) status (ASA 2013) of III or IV (Giger 2006). Lower pressures of pneumoperitoneum have been used to decrease the cardiopulmonary changes and have been considered in a different review (Gurusamy 2009). Helium insufflation is an alternative to CO₂ insufflation (Neuhaus 2001) and has been reported to have little or no effect on pulmonary function in pigs (Junghans 1997).

Abdominal wall lift has been suggested as an alternative for pneumoperitoneum. The lift uses a special device (for example, Laparolift (Egawa 2006) or Laparo-tensor (Alijani 2004)) introduced through a port in the abdominal wall. Randomised clinical trials have shown that abdominal lift causes fewer cardiopulmonary changes than CO₂ pneumoperitoneum (Galizia 2001; Alijani 2004). People undergoing abdominal wall lift were shown to have better mental recovery than the conventional pneumoperitoneum group during the early postoperative period after taking into account the type and duration of anaesthesia, analgesia, and the end-tidal CO₂ (Alijani 2004). However, physical retraction of the abdominal wall causes more abdominal pain than laparoscopy using pneumoperitoneum (Casati 1997). Abdominal wall lift has also been criticised for providing poor exposure that may necessitate cross-over to pneumoperitoneum (Vezakis 1999), at which time a leak-proof seal is difficult to achieve (Vezakis 1999), or additional ports for adequate exposure (Vezakis 1999).

This is an update of our systematic review comparing abdominal lift versus pneumoperitoneum (Gurusamy 2008).

Objectives

To assess the benefits and harms of abdominal wall lift versus pneumoperitoneum in people undergoing laparoscopic cholecystectomy.

Methods

Criteria for considering studies for this review

Types of studies

We included all randomised clinical trials which compared abdominal wall lift to pneumoperitoneum in people undergoing laparoscopic cholecystectomy (irrespective of language, blinding, publication status, or sample size). We also included randomised trials which compared abdominal wall lift in combination with pneumoperitoneum versus pneumoperitoneum alone.

We excluded quasi-randomised studies, where the method of allocating participants to a treatment was not strictly random (for example, date of birth, hospital record number, alternation).

Types of participants

People undergoing laparoscopic cholecystectomy (elective or emergency) for any reason (symptomatic gallstones, acalculous cholecystitis, gallbladder polyp, or any other condition).

Types of interventions

  1. Abdominal wall lift (irrespective of the size and shape) with pneumoperitoneum versus pneumoperitoneum alone (irrespective of the gas used).

  2. Abdominal wall lift (irrespective of the size and shape) versus pneumoperitoneum alone (irrespective of the gas used).

Co-interventions were allowed if used equally in all the intervention groups of the trial.

Types of outcome measures

Primary outcomes
  1. Mortality.

  2. Serious adverse events: adverse events were defined as any untoward medical occurrence not necessarily having a causal relationship with the treatment, but resulting in a dose reduction or discontinuation of treatment (ICH-GCP 1997); serious adverse events were defined as any event that would increase mortality, was life-threatening, required inpatient hospitalisation, resulted in a persistent or significant disability, or any important medical event which might have jeopardised the patient or required intervention to prevent it.

  3. Quality of life.

Secondary outcomes
  1. Conversion to open cholecystectomy.

  2. Operating time.

  3. Proportion discharged as a day-procedure.

  4. Pain (visual analogue scale) between four and eight hours (rest pain, if available).

Due to the many outcomes assessed, we interpret our findings conservatively.

Search methods for identification of studies

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register (Gluud 2013) and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded (Royle 2003). We have given the search strategies in Appendix 1 with the time spans for the searches (last date February 2013).

We also searched the reference lists of the identified trials to identify further relevant trials.

Data collection and analysis

Trial selection and extraction of data

KSG and RK or KS, independently of each other, identified the trials for inclusion. KSG and RK or KS also listed the excluded studies with the reasons for the exclusion. BRD adjudicated any differences in opinion.

Both authors independently extracted the following data.

  1. Year and language of publication.

  2. Country.

  3. Year of conduct of the trial.

  4. Inclusion and exclusion criteria.

  5. Sample size.

  6. Population characteristics such as age and sex ratio.

  7. Antibiotic prophylaxis.

  8. The gas used for creating pneumoperitoneum.

  9. Pressure of pneumoperitoneum.

  10. Device used for abdominal lift (name and type).

  11. Outcomes (mentioned above).

  12. Risk of bias (described below).

We sought any unclear or missing information by contacting the authors of the individual trials. If there was any doubt whether the trials shared the same participants, completely or partially (by identifying common authors and centres), we contacted the authors of the trials to clarify whether the trial report had been duplicated.

We resolved any differences in opinion through discussion. BRD adjudicated any differences in opinion.

Assessment of risk of bias

The authors assessed the methodological quality of the trials independently without masking of the trial names. We followed the instructions given in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011) and the Cochrane Hepato-Biliary Group Module (Gluud 2013). Due to the risk of biased overestimation of intervention effects in randomised trials with inadequate risk of bias domains (Schulz 1995; Moher 1998; Kjaergard 2001; Wood 2008; Lundh 2012; Savovic 2012a; Savovic 2012b), we looked at the influence of these domains on the results.

Allocation sequence generation 
  • Low risk of bias: sequence generation was achieved using computer random number generation or a random number table. Drawing lots, tossing a coin, shuffling cards, and throwing dice were adequate if performed by an independent adjudicator.

  • Uncertain risk of bias: the trial was described as randomised, but the method of sequence generation was not specified.

  • High risk of bias: the sequence generation method was not, or may not have been, random. Quasi-randomised studies, those using dates, names, or admission numbers in order to allocate patients, are inadequate and were excluded for the assessment of benefits but not for assessing harms.

Allocation concealment
  • Low risk of bias: allocation was controlled by a central and independent randomisation unit; sequentially numbered, opaque and sealed envelopes; or similar so that intervention allocations could not have been foreseen in advance of or during enrolment.

  • Uncertain risk of bias: the trial was described as randomised, but the method used to conceal the allocation was not described so that intervention allocations may have been foreseen in advance of or during enrolment.

  • High risk of bias: if the allocation sequence was known to the investigators who assigned participants or if the study was quasi-randomised. Quasi-randomised studies were excluded for the assessment of benefits but not for assessing harms.

Blinding of participants and personnel
  • Low risk of bias: blinding was performed adequately, or the outcome measurement was not likely to be influenced by lack of blinding.

  • Uncertain risk of bias: there was insufficient information to assess whether the type of blinding used was likely to introduce bias in the estimate of effect.

  • High risk of bias: no blinding or incomplete blinding, and the outcome or the outcome measurement was likely to be influenced by lack of blinding.

Blinding of outcome assessors
  • Low risk of bias: blinding was performed adequately, or the outcome measurement was not likely to be influenced by lack of blinding.

  • Uncertain risk of bias: there was insufficient information to assess whether the type of blinding used was likely to introduce bias in the estimate of effect.

  • High risk of bias: no blinding or incomplete blinding, and the outcome or the outcome measurement was likely to be influenced by lack of blinding.

Incomplete outcome data
  • Low risk of bias: the underlying reasons for missing data were unlikely to make treatment effects depart from plausible values, or proper methods were employed to handle missing data.

  • Uncertain risk of bias: there was insufficient information to assess whether the missing data mechanism in combination with the method used to handle missing data were likely to introduce bias in the estimate of effect.

  • High risk of bias: the crude estimate of effects (e.g., complete case estimate) was clearly biased due to the underlying reasons for missing data, and the methods used to handle missing data were unsatisfactory.

Selective outcome reporting
  • Low risk of bias: pre-defined or clinically relevant and reasonably expected outcomes were reported on.

  • Uncertain risk of bias: not all pre-defined or clinically relevant and reasonably expected outcomes were reported on, or were not reported fully, or it was unclear whether data on these outcomes were recorded or not.

  • High risk of bias: one or more clinically relevant and reasonably expected outcomes were not reported on; data on these outcomes were likely to have been recorded.

Vested interest bias
  • Low risk of bias: if the trial was conducted by a party without any vested interests in the outcome of the trial.

  • Uncertain risk of bias: if it was not clear if the trial was conducted by a party with vested interest in the outcome of the trial.

  • High risk of bias: if the trial was conducted by a party with vested interests in the outcome of the trial (such as abdominal wall lift or pneumoperitoneum device manufacturer).

Trials were divided into two groups: trials with low risk of bias encompassing the trials assessed as being at low risk of bias in all the above domains, and trials with high risk of bias encompassing the trials assessed as being at uncertain or high risk of bias.

Statistical methods

We performed the meta-analyses according to the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011) and the Cochrane Hepato-Biliary Group Module (Gluud 2013). We used the software package Review Manager 5 (RevMan 2012). For dichotomous variables, we calculated the risk ratio (RR) with 95% confidence interval (CI) if there were two or more trials for an outcome. For continuous variables, we calculated the mean difference (MD) or standardised mean difference (SMD) (for outcomes such as quality of life where different scales might have been used) with the 95% CI. For count outcomes such as serious adverse events, we calculated the rate ratio (RaR). For all the outcomes a P value of less than 0.05 was considered statistically significant, even if this included only one trial. We used a random-effects model (DerSimonian 1986) and a fixed-effect model (DeMets 1987) for meta-analysis in the presence of two or more trials included under the outcomes. In the case of discrepancy between the two models, we have reported both results; otherwise we have reported the results of the fixed-effect model. Statistical heterogeneity was explored by the Chi² test with significance set at a P value of 0.10, and the amount of heterogeneity was measured by the I² statistic (Higgins 2002; Higgins 2011).

The analysis was performed on an intention-to-treat basis (Newell 1992) whenever possible using the good outcome and poor outcome scenarios. Otherwise, we adopted the 'available-patient analysis' (Higgins 2011). We did not impute any data for the post-randomisation drop-outs for any of the continuous outcomes.

Trial sequential analysis

We used the trial sequential analysis to control for random errors due to sparse data and repetitive testing of the accumulating data for the primary outcomes (CTU 2011; Thorlund 2011). We added the trials according to the year of publication, and if more than one trial was published in a year, add the trials in alphabetical order according to the last name of the first author. We planned to construct the trial sequential monitoring boundaries on the basis of the required information size (Brok 2008; Wetterslev 2008; Brok 2009; Thorlund 2009, Wetterslev 2009; Thorlund 2010).

We applied trial sequential analysis (CTU 2011; Thorlund 2011) using a required sample size calculated from an alpha error of 0.05, a beta error of 0.20, a control group proportion obtained from the results, and a relative risk reduction of 20% for binary outcomes with two or more trials to determine whether more trials are necessary on this topic (if the trial sequential monitoring boundary and the required information size is reached or the futility zone is crossed, then more trials are unnecessary) (Brok 2008; Wetterslev 2008; Brok 2009; Thorlund 2009, Wetterslev 2009; Thorlund 2010). For operating time, the required sample size was calculated from an alpha error of 0.05, a beta error of 0.20, the variance estimated from the meta-analysis results of low risk of bias trials, and a minimal clinically relevant difference of 15 minutes. For pain scores, we planned to use a minimal clinically relevant difference of 1 cm with the other parameters being the same as operating time. It is not possible to perform trial sequential analysis for rate ratios or standardised mean difference and so we did not perform trial sequential analysis for rate of serious adverse events and quality of life.

Subgroup analysis

We intended to perform the following subgroup analyses.

  • Trials with low bias risk compared to trials with high bias risk.

  • Trials with participants belonging to American Society of Anesthesiology (ASA) I or ASA II (mild or no disease) compared to ASA III or ASA IV (severe systemic disease) status.

  • Emergency compared to elective laparoscopic cholecystectomy.

  • Different gases used for pneumoperitoneum.

  • Different pressures used for pneumoperitoneum.

  • Different devices used for abdominal wall lift.

Reporting bias

We planned to use a funnel plot to explore bias (Egger 1997; Macaskill 2001), using asymmetry in the funnel plot of trial size against treatment effect to assess this bias. We planned to perform the linear regression approach described by Egger 1997 to determine the funnel plot asymmetry. We planned to do this for primary outcomes only. Selective outcome reporting where the primary outcomes were not reported on was also considered as evidence for reporting bias.

Summary of findings

We planned to present all the outcomes with at least two trials included in the meta-analysis in the summary of findings tables prepared using GradePro 3.6.

Results

Description of studies

We identified a total of 1057 references through electronic searches of the Cochrane Hepato-Biliary Group Controlled Trials Register and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (n = 202), MEDLINE (n = 240), EMBASE (n = 233), and Science Citation Index Expanded (n = 382). We excluded 465 duplicates and 552 clearly irrelevant references through reading abstracts. Forty references were retrieved for further assessment. One reference was identified through scanning reference lists of the identified randomised trials. We excluded seven references for the reasons listed under the table 'Characteristics of excluded studies'. Thirty-four references of 23 randomised trials involving 904 patients fulfilled the inclusion criteria. All 23 were completed trials and 20 provided data for the meta-analysis. The reference flow is shown in Figure 1. Details about the sample size; patient characteristics; the inclusion and exclusion criteria used in the trials; subcutaneous or intra-peritoneal lift; and the risk of bias in the trials are shown in the table 'Characteristics of included studies'.

Figure 1.

Study flow diagram.

Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum

A total of 130 participants who underwent elective laparoscopic cholecystectomy were randomised in five trials (Lindgren 1995; Koivusalo 1996b; Koivusalo 1997b; Meijer 1997; Alijani 2004) to abdominal wall lift with pneumoperitoneum (n = 53) versus pneumoperitoneum (n = 52). One trial (Koivusalo 1997b) which included 25 people did not state the number in each group. The number of participants in each trial ranged from 18 to 40. We were not able to establish the percentage of women in one trial (Koivusalo 1997b). The percentage of women in the remaining trials was 87.9%. We were not able to obtain the mean age of participants in two trials (Koivusalo 1997b; Meijer 1997). The mean age of participants in the remaining trials was 50.8 years. All the trials included patients of ASA I or ASA II status (no or mild systemic disease). The main outcomes were cardiopulmonary variables, surgical morbidity, operating time, pain, and hospital stay. The outcomes reported by individual trials are reported in the table 'Characteristics of included studies'.

Abdominal wall lift versus pneumoperitoneum

A total of 774 participants who underwent elective laparoscopic cholecystectomy were randomised in 18 trials (Kitano 1993; Koivusalo 1996a; Koivusalo 1997a; Yoshida 1997; Ninomiya 1998; Gamon 1999; Vezakis 1999; Tanpravoon 2000; Galizia 2001; Larsen 2001; Ortiz-Oshiro 2001; Uen 2002; Andersson 2003; Larsen 2004; Egawa 2006; Talwar 2006; Uen 2007; Koivusalo 2008) to abdominal wall lift (n = 338) versus pneumoperitoneum (n = 352). One trial which included 84 participants did not state the number in each group (Tanpravoon 2000). The number of participants in each trial ranged from 10 to 95. The percentage of women in the trials ranged between 12.5% and 100% in the trials that reported this. The average age of participants in the trials ranged between 37 and 74 years, in the trials that reported this. Nine trials (Koivusalo 1996a; Koivusalo 1997a; Gamon 1999; Vezakis 1999; Galizia 2001; Larsen 2001; Uen 2002; Andersson 2003; Egawa 2006) included patients of ASA I or II status (low anaesthetic risk). Among the other five trials, two trials (Yoshida 1997; Ninomiya 1998) excluded people with cardiac or pulmonary diseases. One trial (Ortiz-Oshiro 2001) included patients of ASA I to IV status (all except moribund patients). One trial included patients with ASA II or ASA IV status (at high anaesthetic risk). The participants' general or cardiopulmonary health status was not stated in two trials (Kitano 1993; Larsen 2004). The outcomes reported by the trials are shown in the table 'Characteristics of included studies'.

Risk of bias in included studies

The risk of bias in the trials is shown in Figure 2 and Figure 3. None of the trials was at low risk of bias.

Figure 2.

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

Figure 3.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Effects of interventions

See: Summary of findings for the main comparison Abdominal lift for laparoscopic cholecystectomy; Summary of findings 2 Abdominal lift for laparoscopic cholecystectomy

The summary measures used were relative risk (RR), rate ratio (RaR), mean difference (MD), and standardised mean difference (SMD). The 95% confidence intervals (95% CI) are also stated. The main results are summarised in Summary of findings for the main comparison and Summary of findings 2. As mentioned in the Methods section, the results of the random-effects model were reported only if they were different from the fixed-effect model.

Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum

Mortality

There was no mortality in either group in the two trials that reported this outcome (Meijer 1997; Alijani 2004) (Analysis 1.1). Since there was no mortality in either group, we were unable to use the control group proportion for the calculation of the required information size of the trial sequential analysis. Instead, we used a proportion of 0.2% in the control group based on data from approximately 30,000 patients included in a database in Switzerland (Giger 2011). The proportion of information accrued was only 0.02% of the diversity-adjusted required information size and so the trial sequential monitoring boundaries were not drawn (Figure 4). The cumulative Z-curve does not cross the conventional statistical boundaries.

Figure 4.

Trial sequential analysis of mortality (abdominal wall lift with pneumoperitoneum versus pneumoperitoneum)
The diversity-adjusted required information size (DARIS) was calculated to 352,564 patients, based on the proportion of patients in the control group with the outcome of 0.2%, a relative risk reduction of 20%, an alpha of 5%, a beta of 20%, and a diversity of 0%. To account for zero event groups, a continuity correction of 0.01 was used in the calculation of the cumulative Z-curve (blue line). After accruing a total of 397 patients in seven trials, only 0.12% of the DARIS has been reached. Accordingly, the trial sequential analysis does not show the required information size and the trial sequential monitoring boundaries. As shown, the conventional boundaries have also not been crossed by the cumulative Z-curve.

Serious adverse events

There was no significant difference between the two groups (RaR 1.00; 95% CI 0.14 to 7.10) (Alijani 2004) (Analysis 1.2). In this trial there were two bile leaks, the treatment for which was not reported. Including these bile leaks in the analysis did not result in a change in the results (RaR 1.99; 95% CI 0.36 to 10.97) (Alijani 2004) (Analysis 1.2). There were no serious adverse events in another trial (Meijer 1997). Trial sequential analysis cannot be performed for rate ratios.

Quality of life

None of the trials reported quality of life.

Conversion to open cholecystectomy

None of the participants required conversion to open cholecystectomy in the two trials that reported this outcome (Meijer 1997; Alijani 2004) (Analysis 1.3). Since there was no conversion to open cholecystectomy in either group, we were unable to use the control group proportion for the calculation of the required information size of the trial sequential analysis. Instead, we used a proportion of 5% in the control group based on data from approximately 500,000 patients included in a database in USA (Livingston 2004). The proportion of information accrued was only 0.43% of the diversity-adjusted required information size and so the trial sequential monitoring boundaries were not drawn (Figure 5). The cumulative Z-curve does not cross the conventional statistical boundaries.

Figure 5.

Trial sequential analysis of conversion to open cholecystectomy (abdominal wall lift with pneumoperitoneum versus pneumoperitoneum)
The diversity-adjusted required information size (DARIS) was calculated to 13,493 patients, based on the proportion of patients in the control group with the outcome of 5%, a relative risk reduction of 20%, an alpha of 5%, a beta of 20%, and a diversity of 0%. To account for zero event groups, a continuity correction of 0.01 was used in the calculation of the cumulative Z-curve (blue line). After accruing a total of 58 patients in two trials, only 0.43% of the DARIS has been reached. Accordingly, the trial sequential analysis does not show the required information size and the trial sequential monitoring boundaries. As shown, the conventional boundaries have also not been crossed by the cumulative Z-curve.

Operating time

The operating time was significantly longer in those who underwent laparoscopic cholecystectomy using abdominal wall lift versus those who underwent laparoscopic cholecystectomy using pneumoperitoneum (MD 15.61 minutes; 95% CI 4.01 to 27.22; P = 0.008) (heterogeneity: I² = 39%; P = 0.18) by the fixed-effect model (Lindgren 1995; Koivusalo 1996b; Meijer 1997; Alijani 2004) (Analysis 1.4). There was no significant difference in the groups when the random-effects model was adopted (MD 13.39 minutes; 95% CI -2.73 minutes to 29.51 minutes). Trial sequential analysis of operating time showed that the cumulative Z-curve does not cross the trial sequential monitoring boundaries suggesting that the observed differences could be due to random error and that more trials are necessary to conclude that laparoscopic cholecystectomy performed by abdominal wall lift with pneumoperitoneum takes longer operating time than that performed with pneumoperitoneum (Figure 6).

Figure 6.

Trial sequential analysis of operating time (abdominal wall lift with pneumoperitoneum versus pneumoperitoneum)
Trial sequential analysis of operating time showing that the cumulative Z-curve crosses the conventional boundary after the third trial. However, the cumulative Z-curve does not cross the trial sequential monitoring boundaries (inward sloping red lines). The diversity-adjusted required information size (DARIS) was 505 participants based on a minimal relevant difference (MIRD) of 15 minutes, a variance (VAR) of 1875.28, an alpha (a) of 5%, a beta (b) of 20%, and a diversity (D2) of 48.17%. After accruing 107 participants in four trials, the information fraction was too small (21.18%) to draw the futility area. The results suggest that the observed statistical significance favouring pneumoperitoneum may be due to random error and that more trials are necessary to conclude that laparoscopic cholecystectomy performed by abdominal wall lift with pneumoperitoneum takes longer operating time than that performed with pneumoperitoneum.

Proportion discharged as day-procedure patients

None of the trials reported the proportion of people who were discharged as laparoscopic cholecystectomy day-patients.

Pain (four to eight hours)

None of the trials reported the pain scores between four and eight hours post-operatively.

Abdominal wall lift without pneumoperitoneum versus pneumoperitoneum

Mortality

There was no mortality in either group in the seven trials that reported this outcome (Kitano 1993; Koivusalo 1996a; Uen 2002; Larsen 2004; Talwar 2006; Uen 2007; Koivusalo 2008) (Analysis 2.1). Since there was no mortality in either group, we were unable to use the control group proportion for the calculation of the required information size of the trial sequential analysis as before. Instead, we used a proportion of 0.2% in the control group based on data from approximately 30,000 patients included in a database in Switzerland as before (Giger 2011). The proportion of information accrued was only 0.11% of the diversity-adjusted required information size and so the trial sequential monitoring boundaries were not drawn (Figure 7). The cumulative Z-curve does not cross the conventional statistical boundaries.

Figure 7.

Trial sequential analysis of mortality (abdominal wall lift without pneumoperitoneum versus pneumoperitoneum)
The diversity-adjusted required information size (DARIS) was calculated to 352,564 patients, based on the proportion of patients in the control group with the outcome of 0.2%, a relative risk reduction of 20%, an alpha of 5%, a beta of 20%, and a diversity of 0%. To account for zero event groups, a continuity correction of 0.01 was used in the calculation of the cumulative Z-curve (blue line). After accruing a total of 393 patients in seven trials, only 0.11% of the DARIS has been reached. Accordingly, the trial sequential analysis does not show the required information size and the trial sequential monitoring boundaries. As shown, the conventional boundaries have also not been crossed by the cumulative Z-curve.

Serious adverse events

There was no significant difference between the two groups (RaR 1.73; 95% CI 0.35 to 8.61; heterogeneity: I² = 0%; P = 0.37) (Kitano 1993; Uen 2002; Koivusalo 2008) (Analysis 2.2). There was no change in the results by adopting the random-effects model. Three other trials reported that there were no serious adverse events in the peri-operative period (Koivusalo 1996a; Talwar 2006; Uen 2007). There was no significant difference in the proportion of people who developed serious adverse events (RR 2.01; 95% CI 0.52 to 7.80; heterogeneity: I² = 4%; P = 0.35). The trial sequential analysis showed that the proportion of information accrued was only 0.59% of the diversity-adjusted required information size and so the trial sequential monitoring boundaries were not drawn (Figure 8). The cumulative Z-curve does not cross the conventional statistical boundaries.

Figure 8.

Trial sequential analysis of serious adverse events (abdominal wall lift without pneumoperitoneum versus pneumoperitoneum)
The diversity-adjusted required information size (DARIS) was calculated to 58,231 patients, based on the proportion of patients in the control group with the outcome of 1.2%, a relative risk reduction of 20%, an alpha of 5%, a beta of 20%, and a diversity of 0%. To account for zero event groups, a continuity correction of 0.01 was used in the calculation of the cumulative Z-curve (blue line). After accruing a total of 343 patients in six trials, only 0.59% of the DARIS has been reached. Accordingly, the trial sequential analysis does not show the required information size and the trial sequential monitoring boundaries. As shown, the conventional boundaries have also not been crossed by the cumulative Z-curve.

Quality of life

None of the trials reported quality of life.

Conversion to open cholecystectomy

There was no significant difference in the proportion of people who required conversion to open cholecystectomy (RR 0.76; 95% CI 0.26 to 2.21; P = 0.62; heterogeneity: I² = 55%; P = 0.11) (Kitano 1993; Koivusalo 1997a; Yoshida 1997; Gamon 1999; Vezakis 1999; Galizia 2001; Larsen 2001; Uen 2002; Larsen 2004; Talwar 2006; Koivusalo 2008) (Analysis 2.4). There was no change in the results by adopting the random-effects model. The trial sequential analysis showed that the proportion of information accrued was only 2.01% of the diversity-adjusted required information size and so the trial sequential monitoring boundaries were not drawn (Figure 9). The cumulative Z-curve does not cross the conventional statistical boundaries.

Figure 9.

Trial sequential analysis of conversion to open cholecystectomy (abdominal wall lift without pneumoperitoneum versus pneumoperitoneum)
The diversity-adjusted required information size (DARIS) was calculated to 22,911 patients, based on the proportion of patients in the control group with the outcome of 3%, a relative risk reduction of 20%, an alpha of 5%, a beta of 20%, and a diversity of 0%. To account for zero event groups, a continuity correction of 0.01 was used in the calculation of the cumulative Z-curve (blue line). After accruing a total of 560 participants in 11 trials, only 2.01% of the DARIS has been reached. Accordingly, the trial sequential analysis does not show the required information size and the trial sequential monitoring boundaries. As shown, the conventional boundaries have also not been crossed by the cumulative Z-curve.

Operating time

The operating time was significantly longer in those who underwent laparoscopic cholecystectomy using abdominal wall lift compared to those who underwent laparoscopic cholecystectomy using pneumoperitoneum (MD 6.87 minutes; 95% CI 4.74 minutes to 9.00 minutes; P < 0.0001; heterogeneity: I² = 67%; P < 0.001) (Kitano 1993; Koivusalo 1996a; Koivusalo 1997a; Yoshida 1997; Ninomiya 1998; Gamon 1999; Vezakis 1999; Tanpravoon 2000; Galizia 2001; Larsen 2001; Ortiz-Oshiro 2001; Uen 2002; Andersson 2003; Larsen 2004; Egawa 2006; Talwar 2006; Uen 2007; Koivusalo 2008) (Analysis 2.5; Analysis 2.6). There was no change in the results by adopting the random-effects model. The trial sequential analysis showed that the trial sequential monitoring boundary favouring laparoscopic cholecystectomy performed using pneumoperitoneum was crossed by the cumulative Z-curve (Figure 10), suggesting that new trials are unlikely to dispute the finding that the operating time is significantly longer in the abdominal wall lift group compared to the pneumoperitoneum group.

Figure 10.

Trial sequential analysis of operating time (abdominal wall lift without pneumoperitoneum versus pneumoperitoneum)
Trial sequential analysis of operating time showing that the cumulative Z-curve crosses the trial sequential monitoring boundary after the tenth trial. The diversity-adjusted required information size (DARIS) was 304 participants based on a minimal relevant difference (MIRD) of 15 minutes, a variance (VAR) of 384.2, an alpha (a) of 5%, a beta (b) of 20%, and a diversity (D2) of 82.29%. The results are compatible with significantly higher operating time in the abdominal wall lift group compared with pneumoperitoneum group without risk of random errors.

Proportion discharged as day-procedure patients

There was no significant difference in the proportion of people who were discharged as day-patients between the two groups (RR 1.67; 95% CI 0.85 to 3.26; P = 0.14; heterogeneity: I² = 75%; P = 0.05) (Koivusalo 1996a; Vezakis 1999) (Analysis 2.7). There was no change in the results by adopting the random-effects model. The trial sequential analysis showed that the proportion of information accrued was only 0.47% of the diversity-adjusted required information size and so the trial sequential monitoring boundaries were not drawn (Figure 11). The cumulative Z-curve does not cross the conventional statistical boundaries.

Figure 11.

Trial sequential analysis of proportion discharged as day-patient laparoscopic cholecystectomy (abdominal wall lift without pneumoperitoneum versus pneumoperitoneum)
The diversity-adjusted required information size (DARIS) was calculated to 13,293 patients, based on the proportion of patients in the control group with the outcome of 29.0%, a relative risk reduction of 20%, an alpha of 5%, a beta of 20%, and a diversity of 86.45%. After accruing a total of 62 patients in two trials, only 0.47% of the DARIS has been reached. Accordingly, the trial sequential analysis does not show the required information size and the trial sequential monitoring boundaries. As shown, the conventional boundaries have also not been crossed by the cumulative Z-curve (blue line).

Pain (four to eight hours)

None of the trials reported the pain scores between four and eight hours post-operatively.

Subgroup analysis

None of the planned subgroup analyses was performed because of the few trials included in each outcome. A post hoc subgroup and sensitivity analysis included all the trials irrespective of whether pneumoperitoneum was used along with abdominal wall lift. This revealed that there was no change in the conclusions on combining the two main analyses. There were no significant subgroup differences for any of the comparisons in which this analysis was possible (Analysis 3.1; Analysis 3.2; Analysis 3.3).

Trial sequential analysis

Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum
We were unable to perform trial sequential analyses for the comparison abdominal wall lift with pneumoperitoneum versus pneumoperitoneum since there was no mortality in any of the trials that reported mortality, and none of the trials reported the proportion of patients with serious adverse events or the quality of life.

Abdominal wall lift without pneumoperitoneum versus pneumoperitoneum
For the comparison abdominal wall lift without pneumoperitoneum versus pneumoperitoneum, we performed a trial sequential analysis (TSA) only for the proportion of people with serious adverse events. The trial sequential analysis showed that the information fraction was too small to draw any definite conclusions. We performed trial sequential analysis using the proportion with serious adverse events in the control group (Pc) of 1.2%, a relative risk reduction (RRR) of 20%, an alpha error of 0.05, a beta error of 0.20, and a diversity (D) (ie, D²) of 0%. The diversity-adjusted required information size (DARIS) is 58,231 patients and with only 341 patients randomised, we have only obtained 0.59% of the required information size. The TSA programme does not show the required information size or the trial sequential monitoring boundaries. The horizontal dashed lines are equivalent to a two-sided P value of 0.05 (Figure 8).

There was no mortality in either group in the trials that reported this outcome and none of the trials reported the quality of life, so TSA was not performed.

Reporting bias

The number of trials that reported serious adverse events were few, so that we did not produce a funnel plot or Egger's linear regression approach (Egger 1997). However, fewer than half the trials reported the primary outcomes of the present systematic review, indicating reporting bias.

Discussion

The abdominal wall lift was introduced to laparoscopic surgery primarily as a method to reduce the cardiopulmonary changes which are seen with a carbon dioxide pneumoperitoneum. The previous version of this systematic review suggested that abdominal wall lift is associated with fewer cardiopulmonary changes during surgery (Gurusamy 2008). We assessed whether the reduction in these cardiopulmonary changes translates to any significant advantages to the patients or healthcare funders. Based on the evidence from this review, there does not appear to be any benefit in performing abdominal wall lift with or without pneumoperitoneum compared to carbon dioxide pneumoperitoneum.

There was no mortality in any of the trials that reported this outcome. Mortality is a rare event in laparoscopic cholecystectomy. Peri-operative complications were reported in only eight of the 24 included trials. Peri-operative cardiopulmonary complications were rare during or after laparoscopic cholecystectomy in the trials that reported the complications. Based on the decreased cardiopulmonary changes with abdominal lift (Gurusamy 2008), it is unlikely that abdominal wall lift results in greater morbidity due to cardiopulmonary complications. The main issue in abdominal wall lift is adequate visualisation of the structures so that the surgery can be performed safely. There is some weak evidence that the operating time was longer in the abdominal wall lift group compared to pneumoperitoneum. This could be related to the poor exposure or the time required to establish the exposure. In the absence of this information, it is difficult to comment upon the reason for the increased operating time, but one cannot rule out poor exposure which can be potentially detrimental to the patient. As mentioned earlier, only a third of the trials reported on the safety of abdominal wall lift. There have been no larger cohort studies or case-control studies that show potential advantages of abdominal wall lift over pneumoperitoneum with regards to complications. However, the majority of the participants included in this review had low anaesthetic risk. This review is therefore applicable only to people at low anaesthetic risk.

Quality of life was not reported in any of the trials. Quality of life is an important patient-oriented outcome and is one of the ways that the cost effectiveness of an intervention is assessed. In the absence of such information, it is not possible to determine whether one intervention is more cost-effective than another. This information is particularly important for state-funded health systems in light of the fact that there is weak evidence that the operating time is longer in those undergoing laparoscopic cholecystectomy using the abdominal wall lift method.

There were no significant differences in the other important outcomes that are of interest to patients and healthcare funders, such as conversion to open cholecystectomy and the proportion discharged as laparoscopic cholecystectomy day-patients.

Pain between four and eight hours post-procedure is an important outcome from the patient and healthcare funder perspectives. Pain is one of the important reasons for failed day-patient laparoscopic cholecystectomy (Gurusamy 2008a; Gurusamy 2008b). None of the trials reported this outcome. Future trials should include such outcomes.

In such a situation where the safety of the procedure has not been established completely, with no major advantages over the standard practice, we are unable to recommend abdominal wall lift. In the previous version of the review we did not recommend abdominal wall lift over pneumoperitoneum but mentioned that it was probably safe. While we continue to recommend that abdominal wall lift cannot be preferred over pneumoperitoneum in those at low anaesthetic risk, we have revised our conclusion regarding the safety. We now believe that the safety of abdominal wall lift has not been established and so should be considered only in the trial setting. Our conclusions have been revised from the previous version of the review (Gurusamy 2008) because of the updated version of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), which has resulted in a better understanding of the interpretation of evidence.

Authors' conclusions

Implications for practice

Abdominal wall lift with or without pneumoperitoneum does not seem to be beneficial compared to pneumoperitoneum in any of the patient-oriented or healthcare funder outcomes in low anaesthetic risk people. The safety of abdominal wall lift has to be established. Hence it cannot be recommended routinely.

Implications for research

Future randomised clinical trials with low risk of bias and sufficient sample size are necessary to compare abdominal wall lift with or without pneumoperitoneum versus pneumoperitoneum alone.

The role of laparoscopic cholecystectomy using abdominal wall lift as an alternative to pneumoperitoneum and to open cholecystectomy in those with severe systemic disease (ASA III and ASA IV) also needs further assessment.

Trials need to be conducted and reported according to the CONSORT statement (www.consort-statement.org) (Moher 2001; Boutron 2008; Schulz 2010). Future randomised trials ought to include people at higher anaesthetic risk and to employ blinded assessments of outcomes.

Acknowledgements

To the authors of reports of randomised clinical trials who answered the questions asked (AM Koivusalo and LB Koay).
To the Cochrane Hepato-Biliary Group for the support that they have provided.

To K Samraj, India independently assessed the trials for inclusion and extracted data on included trials for the first version of the review (Gurusamy 2008).

Review update
Peer Reviewer: Ronald L Koretz, USA.
Contact Editor: Christian Gluud, Denmark.

This project was funded by the National Institute for Health Research (NIHR).

Disclaimer

Department of Health disclaimer: The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, NHS (National Health Service), or the Department of Health.

Data and analyses

Download statistical data

Comparison 1. Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Mortality  Other dataNo numeric data
2 Adverse events1 Rate Ratio (Fixed, 95% CI)Subtotals only
2.1 Serious adverse events1 Rate Ratio (Fixed, 95% CI)1.0 [0.14, 7.10]
2.2 Unknown severity1 Rate Ratio (Fixed, 95% CI)1.99 [0.36, 10.97]
3 Conversion to open cholecystectomy  Other dataNo numeric data
4 Operating time4107Mean Difference (IV, Random, 95% CI)13.39 [-2.73, 29.51]

Analysis 1.1.

Comparison 1 Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, Outcome 1 Mortality.

Mortality
StudyObservation in abdominal wall lift groupObservation in pneumoperitoneum groupStatistical significance
Alijani 20040/20 (0%)0/20 (0%)Not estimable
Meijer 19970/9 (0%)0/9 (0%)Not estimable
Analysis 1.2.

Comparison 1 Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, Outcome 2 Adverse events.

Analysis 1.3.

Comparison 1 Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, Outcome 3 Conversion to open cholecystectomy.

Conversion to open cholecystectomy
StudyObservation in abdominal wall lift groupObservation in pneumoperitoneum groupStatistical significance
Alijani 20040/20 (0%)0/20 (0%)Not estimable
Meijer 19970/9 (0%)0/9 (0%)Not estimable
Analysis 1.4.

Comparison 1 Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, Outcome 4 Operating time.

Comparison 2. Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP)
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Mortality  Other dataNo numeric data
2 Serious adverse events3 Rate Ratio (Fixed, 95% CI)1.73 [0.35, 8.61]
3 Proportion of patients with serious adverse events6343Risk Ratio (M-H, Fixed, 95% CI)2.01 [0.52, 7.80]
4 Conversion to open cholecystectomy11460Risk Ratio (M-H, Fixed, 95% CI)0.76 [0.26, 2.21]
5 Operating time16649Mean Difference (IV, Fixed, 95% CI)6.87 [4.74, 9.00]
6 Operating time (trials that could not be included for the meta-analysis)  Other dataNo numeric data
7 Proportion discharged as day-patient laparoscopic cholecystectomy262Risk Ratio (M-H, Fixed, 95% CI)1.67 [0.85, 3.26]

Analysis 2.1.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 1 Mortality.

Mortality
StudyObservation in abdominal wall lift groupObservation in pneumoperitoneum groupStatistical significance
Kitano 19930/41 (0%)0/42 (0%)Not estimable
Koivusalo 1996a0/13 (0%)0/13 (0%)Not estimable
Koivusalo 20080/10 (0%)0/10 (0%)Not estimable
Larsen 20040/24 (0%)0/26 (0%)Not estimable
Talwar 20060/20 (0%)0/20 (0%)Not estimable
Uen 20020/48 (0%)0/47 (0%)Not estimable
Uen 20070/40 (0%)0/39 (0%)Not estimable
Analysis 2.2.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 2 Serious adverse events.

Analysis 2.3.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 3 Proportion of patients with serious adverse events.

Analysis 2.4.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 4 Conversion to open cholecystectomy.

Analysis 2.5.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 5 Operating time.

Analysis 2.6.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 6 Operating time (trials that could not be included for the meta-analysis).

Operating time (trials that could not be included for the meta-analysis)
StudyObservation in abdominal wall lift groupObservation in pneumoperitoneum groupStatistical significance
Andersson 2003125 minutes (median; 9 patients)120 minutes (median; 10 patients)Not reported
Tanpravoon 2000104 minutes (mean)64.6 minutes (mean)< 0.001
Analysis 2.7.

Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 7 Proportion discharged as day-patient laparoscopic cholecystectomy.

Comparison 3. Abdominal wall lift (AWL) versus pneumoperitoneum (PP) - subgroup analyses
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Serious adverse events5 Rate Ratio (Fixed, 95% CI)Subtotals only
1.1 AWL with pneumoperitoneum2 Rate Ratio (Fixed, 95% CI)1.0 [0.17, 5.77]
1.2 AWL without pneumoperitoneum3 Rate Ratio (Fixed, 95% CI)1.73 [0.35, 8.61]
2 Conversion to open cholecystectomy13518Risk Ratio (M-H, Fixed, 95% CI)0.76 [0.26, 2.21]
2.1 AWL with pneumoperitoneum258Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]
2.2 AWL without pneumoperitoneum11460Risk Ratio (M-H, Fixed, 95% CI)0.76 [0.26, 2.21]
3 Operating time20756Mean Difference (IV, Random, 95% CI)9.20 [4.40, 14.00]
3.1 AWL with pneumoperitoneum4107Mean Difference (IV, Random, 95% CI)13.39 [-2.73, 29.51]
3.2 AWL without pneumoperitoneum16649Mean Difference (IV, Random, 95% CI)8.53 [3.48, 13.58]
Analysis 3.1.

Comparison 3 Abdominal wall lift (AWL) versus pneumoperitoneum (PP) - subgroup analyses, Outcome 1 Serious adverse events.

Analysis 3.2.

Comparison 3 Abdominal wall lift (AWL) versus pneumoperitoneum (PP) - subgroup analyses, Outcome 2 Conversion to open cholecystectomy.

Analysis 3.3.

Comparison 3 Abdominal wall lift (AWL) versus pneumoperitoneum (PP) - subgroup analyses, Outcome 3 Operating time.

Appendices

Appendix 1. Search strategies

DatabasePeriod of searchSearch strategy
Cochrane Hepato-Biliary Group Controlled Trials Register and The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Wiley)Issue 1, 2013#1 MeSH descriptor Cholecystectomy, Laparoscopic explode all trees
#2 (laparoscop* OR coelioscop* OR celioscop* OR peritoneoscop*) AND cholecystectom*
#3 (#1 OR #2)
#4 MeSH descriptor Pneumoperitoneum, Artificial explode all trees
#5 MeSH descriptor Insufflation explode all trees
#6 MeSH descriptor Abdominal Wall explode all trees
#7 pneumoperitoneum OR insufflation OR "abdominal wall lift" OR gasless
#8 (#4 OR #5 OR #6 OR #7)
#9 (#3 AND #8)
MEDLINE (PubMed)1987 to February 2013(laparoscop* OR coelioscop* OR celioscop* OR peritoneoscop*) AND (cholecystectom* OR cholecystectomy, laparoscopic[MeSH]) AND (pneumoperitoneum OR Pneumoperitoneum, Artificial[MeSH] OR insufflation OR insufflation[MeSH] OR "abdominal wall lift" OR Abdominal Wall[MeSH] OR gasless) AND (((randomised controlled trial [pt] OR controlled clinical trial [pt] OR randomised controlled trials [mh] OR random allocation [mh] OR double-blind method [mh] OR single-blind method [mh] OR clinical trial [pt] OR clinical trials [mh] OR ("clinical trial" [tw]) OR ((singl* [tw] OR doubl* [tw] OR trebl* [tw] OR tripl* [tw]) AND (mask* [tw] OR blind* [tw])) OR (placebos [mh] OR placebo* [tw] OR random* [tw] OR research design [mh:noexp]) NOT (animals [mh] NOT human [mh]))))
EMBASE (OvidSP)1987 to February 2013

1. exp CROSSOVER PROCEDURE/

2. exp DOUBLE BLIND PROCEDURE/

3. exp SINGLE BLIND PROCEDURE/

4. exp RANDOMIZED CONTROLLED TRIAL/

5. (((RANDOM* or FACTORIAL* or CROSSOVER* or CROSS) and OVER*) or PLACEBO* or (DOUBL* and BLIND*) or (SINGL* and BLIND*) or ASSIGN* or ALLOCAT* or VOLUNTEER*).af.

6. 1 or 2 or 3 or 4 or 5

7. (laparoscop* or coelioscop* or celioscop* or peritoneoscop*).af.

8. "cholecystectom*".af.

9. 8 and 7

10. exp Cholecystectomy/

11. exp Laparoscopic Surgery/

12. 11 and 10

13. 9 or 12

14. (pneumoperitoneum or insufflation or "abdominal wall lift" or gasless).af.

15. exp Pneumoperitoneum/

16. exp Abdominal Wall/

17. 16 or 15 or 14

18. 6 and 13 and 17

Science Citation Index Expanded (ISI Web of Science)1987 to February 2013#1 TS=(laparoscop* OR coelioscop* OR celioscop* OR peritoneoscop*)
#2 TS=(cholecystectom*)
#3 TS=(pneumoperitoneum OR insufflation OR "abdominal wall lift" OR gasless)
#4 TS=(random* OR blind* OR placebo* OR meta-analysis)
#5 #4 AND #3 AND #2 AND #1

What's new

Last assessed as up-to-date: 19 February 2013.

DateEventDescription
30 April 2013AmendedTwo publications (a full text article and a conference abstract) may be two different randomised trials. We did not receive a reply from the authors on our e-mail sent in February 2007 and July 2013. Only one of the reports contain information that can be used for analysis. So, whether these are two reports of the same trial or two different trials does not affect the meta-analysis in any way. For the purpose of this review, we considered them to be two reports of the same trial.
26 February 2013New citation required and conclusions have changedConclusions partially changed. In the previous version of the review, we did not recommend abdominal wall lift over pneumoperitoneum but mentioned that it was probably safe. While we continue to recommend that abdominal wall lift cannot be preferred over pneumoperitoneum in those at low anaesthetic risk, we have revised our conclusion regarding the safety. We now believe that the safety of abdominal wall lift has not been established and so should be considered only in the trial setting. Our conclusions have been revised from the previous version of the review (Gurusamy 2008) because of the updated version of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), which has resulted in a better understanding of the interpretation of evidence..
19 February 2013New search has been performed

Searches were updated on 19 of February 2013. No new trials were found.

The reference flow was changed due to the updated searches, trial sequential analyses were revised, and the funder who provided funding for the update of this review is now acknowledged.

Contributions of authors

KS Gurusamy wrote the review and assessed the trials for inclusion and extracted data on included trials. R Koti identified new trials and extracted data from them for the update. BR Davidson commented critically on the review and provided advice for improvements.

Declarations of interest

None known.

Sources of support

Internal sources

  • University College London, UK.

External sources

  • National Institute of Health Research, UK.

Differences between protocol and review

Differences between first version and second version of review

  1. The methods of the review have been updated to reflect the recommendations of Version 5.1 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). This has resulted in change of outcomes, the methods of assessing risk of bias, inclusion of summary of findings tables, and better interpretation of the data.

  2. Searches have been updated and four new trials have been identified.

  3. Post hoc subgroup and sensitivity analyses were done, including all the trials irrespective of whether pneumoperitoneum was used along with abdominal wall lift.

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Alijani 2004

MethodsRandomised clinical trial.
Participants

Country: United Kingdom.
Number randomised: 40.
Mean age: 53 years.
Females: 35 (87.5%).

Inclusion criteria:

  1. Elective laparoscopic cholecystectomy

  2. ASA I or II

Exclusion criteria:
Breast feeding.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift with 4 mm Hg pneumoperitoneum (n = 20).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 20).

Device used for abdominal lift: subcutaneous device.

OutcomesThe outcome measures reported were complications, conversion to open cholecystectomy, and operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Low risk

Quote: "Written informed consent was obtained before patients were randomised by selection based on sealed brown envelopes."

Comment: Further details of this method were not available.

Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Low riskComment: There were no post-randomisation drop-outs.
Selective reporting (reporting bias)High riskComment: The treatment of the complications was not stated clearly so as to determine their severity..
Vested interest biasUnclear risk

Quote: "This work was supported in part by a grant fromTayside University Hospitals NHS Trust, Scotland."

Comment: Not clear whether this was the only source of support.

Andersson 2003

MethodsRandomised clinical trial.
Participants

Country: Sweden.
Number randomised: 20.
Mean age: 39 years.
Females: 14 (70%).

Inclusion criteria:

  1. ASA I

  2. Requires laparoscopic cholecystectomy.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 10).
Group 2: pneumoperitoneum with 11 to 13 mm Hg pressure (n = 10).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe outcome measure was operating time.
Notes

One cross-over participant from abdominal wall lift group to control due to poor visualisation.

Attempts were made to contact the author in February 2007.

Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were post-randomisation drop-outs.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear risk

Quote: "This study was supported by Karolinska Institute."

Comment: Not clear whether this was the only source of support.

Egawa 2006

MethodsRandomised clinical trial.
Participants

Country: Japan.
Number randomised: 30.
Mean age: 50 years.
Females: 14 (46.7%).

Inclusion criteria:

  1. Elective laparoscopic cholecystectomy

  2. ASA I or II

  3. Age 38 to 64 years.

Exclusion criteria:
Pre-existing cardiovascular, respiratory or cerebrovascular disease.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 15).
Group 2: pneumoperitoneum with 10 to 12 mm Hg pressure (n = 15).

Device used for abdominal lift: not stated.

OutcomesThe outcome measure reported was operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Galizia 2001

MethodsRandomised clinical trial.
Participants

Country: Italy.
Number randomised: 10.
Mean age: 37 years.
Females: 2 (20%).

Inclusion criteria:

  1. ASA I

  2. Age 45 years or younger

  3. Regular body weight and height.

Exclusion criteria:

  1. Previous abdominal surgery

  2. No gallstone-related complications

  3. Absence of cardiovascular or respiratory dysfunction.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 5).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 5).

Device used for abdominal lift: subcutaneous device.

Another group of participants who were randomised to open cholecystectomy was excluded.

OutcomesThe main outcome measures were conversion to open cholecystectomy and operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear risk

Quote: "A sealed envelope, opened in the operating room, randomised five patients to an open cholecystectomy (OC group), five patients to a CO₂ pneumoperitoneum laparoscopic cholecystectomy (PP group), and five patients to a gasless laparoscopic cholecystectomy (AWL group), respectively."

Comment: This information was not available.

Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Gamon 1999

MethodsRandomised clinical trial.
Participants

Country: Spain.
Number randomised: 30.
Mean age: 55 years.
Females: 22 (73.3%).

Inclusion criteria:

  1. Symptomatic cholelithiasis

  2. ASA I or II.

Exclusion criteria:

  1. Previous abdominal surgery

  2. Concomitant common bile duct stones

  3. Gallbladder cancer.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 15).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 15).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measures were conversion to open cholecystectomy and operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Kitano 1993

MethodsRandomised clinical trial.
Participants

Country: Japan.
Number randomised: 83.
Mean age: 52 years.
Females: 47 (56.6%).

Inclusion criteria:

  1. Radiographic evidence of cholelithiasis

  2. Symptoms consistent with gallbladder disease.

Exclusion criteria:

  1. Previous abdominal surgery

  2. Concomitant common bile duct stones

  3. Gallbladder cancer.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 41).
Group 2: pneumoperitoneum (pressure not stated) (n = 42).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measures were complications and operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Low riskComment: There were no postrandomisation drop-outs.
Selective reporting (reporting bias)Low riskComment: All important outcomes were reported.
Vested interest biasUnclear riskComment: This information was not available.

Koivusalo 1996a

MethodsRandomised clinical trial.
Participants

Country: Finland.
Number randomised: 26.
Mean age: 44 years.
Females: 24 (92.3%).

Inclusion criteria:
1. Elective cholecystectomy
2. ASA I or II.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 13).
Group 2: pneumoperitoneum with 12 to 15 mm Hg pressure (n = 13).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measures were complications, operating time, and proportion discharged as day-patient laparoscopic cholecystectomy.
NotesAttempts were made to contact the author in February 2007 and July 2013.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)Low riskComment: All important outcomes were reported.
Vested interest biasUnclear riskComment: This information was not available.

Koivusalo 1996b

MethodsRandomised clinical trial.
Participants

Country: Finland.
Number randomised: 24.
Mean age: 49 years.
Females: 22 (91.7%).

Inclusion criteria:

  1. Elective cholecystectomy

  2. ASA I or II.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift with or without pneumoperitoneum (pressure not stated) (n = 12).
Group 2: pneumoperitoneum with 12 to 15 mm Hg pressure (n = 12).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measure was operating time.
NotesAttempts were made to contact the author in February 2007 and July 2013.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Koivusalo 1997a

MethodsRandomised clinical trial.
Participants

Country: Finland.
Number randomised: 29.
Mean age: 46 years.
Females: not stated.

Inclusion criteria:

  1. Elective cholecystectomy

  2. ASA I or II

Exclusion criteria:

  1. Bronchial asthma

  2. Chronic pulmonary disease

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 14).
Group 2: pneumoperitoneum with 12 to 13 mm Hg pressure (n = 15).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measures were conversion to open cholecystectomy and operating time.
Notes

Withdrawal, one because of malpositioning of nasogastric tube (in this trial, gastric mucosal pH was measured).

Attempts were made to contact the author in February 2007 and July 2013.

Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were postrandomisation drop-outs.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Koivusalo 1997b

MethodsRandomised clinical trial.
Participants

Country: Finland.
Number randomised: 25.
Mean age: not stated.
Females: not stated.

Inclusion criteria:

  1. Elective cholecystectomy

  2. ASA I or II.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift with or without pneumoperitoneum (pressure not stated) (n = not stated).
Group 2: pneumoperitoneum with 12 to 15 mm Hg pressure (n = not stated).

Device used for abdominal lift: intra-peritoneal device.

OutcomesNone of the outcomes of interest for this review were reported in this trial.
NotesAttempts were made to contact the author in February 2007 and July 2013.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Koivusalo 2008

MethodsRandomised clinical trial.
Participants

Country: Finland.
Number randomised: 20.
Mean age: 74 years.
Females: 11 (55%).
Inclusion criteria:
1. Patients undergoing  elective laparoscopic cholecystectomy without cholangiography or choledochectomy
2. ASA III and IV

Exclusion criteria:
1. Patients with an unacceptably high risk of perioperative morbidity such as those with arterial oxygen tension (PaO₂) at rest less than 8 kPa and/or CO₂ tension (PaCO₂) greater than 7.5 kPa, clinically significant aortic valve stenosis or mitral insufficiency, unstable angina pectoris, terminal renal insufficiency, hepatic cirrhosis, or morbid obesity (body mass index [BMI]) > 35).

2. Patients with psychiatric or neurologic conditions impairing their ability to cooperate.

Interventions

The participants were randomised to the following groups:
Group 1: abdominal wall lift (n = 10).
Group 2: pneumoperitoneum with 8 to 12 mm Hg pressure (n = 10).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe outcome reported was mortality, serious adverse events, and operating time.
NotesAuthors replied to questions related to the trial in February 2012.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Low riskQuote: "'Open LCC' and 'retractor' were written in a small paper,then it was sealed in on envelope. All the 'envelopes' ( 20 pieces) were made at the same time. when the eligible patient was identified, he/she was asked for the approval to the study. after that the anaesthesiologist pulled the envelope, and told the surgeon which technique to use." (author replies).
Allocation concealment (selection bias)Unclear risk

Quote: "'Open LCC' and 'retractor' were written in a small paper,then it was sealed in on envelope. All the 'envelopes' ( 20 pieces) were made at the same time. when the eligible patient was identified, he/she was asked for the approval to the study. after that the anaesthesiologist pulled the envelope, and told the surgeon which technique to use." (author replies).

Comment: Further information regarding opacity was not available.

Blinding of participants and personnel (performance bias)
All outcomes
Low risk

Quote: "An independent doctor, not aware of the method used. Also the patients were unaware of the method. They had similar 'plasters' in their stomachs" (author replies). 

Comment: It is not possible to blind the healthcare providers regarding the groups.

Blinding of outcome assessment (detection bias)
All outcomes
Low riskQuote: "An in depended doctor, not aware of the method used. Also the patients were unaware of the method. They had similar 'plasters' in their stomachs" (author replies). 
Incomplete outcome data (attrition bias)
All outcomes
Low riskQuote: "All met the inclusion criteria and thus no patients needed to be excluded."
Selective reporting (reporting bias)Low riskComment: Mortality and serious adverse events were not reported.
Vested interest biasLow riskQuote: "With governmental investigational money" (author replies).

Larsen 2001

MethodsRandomised clinical trial.
Participants

Country: Denmark.
Number randomised: 50.
Mean age: 51 years.
Females: 35 (70%).

Inclusion criteria:

  1. Elective participants

  2. ASA I or II

  3. > 18 years

  4. BMI of 30 or less.

Exclusion criteria:

  1. Acute pancreatitis

  2. Cholecystitis

  3. Cholangitis

  4. Blood diseases

  5. Rheumatic diseases

  6. Acute infectious diseases

  7. Renal diseases

  8. Liver diseases.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 24).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 26).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measures were complications, conversion to open cholecystectomy, and operating time.
Notes

One cross-over from abdominal wall lift to control group because of poor visualisation.

Attempts were made to contact the author in February 2007.

Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Low riskQuote: "The allocation sequence was generated by random numbers".
Allocation concealment (selection bias)Unclear risk

Quote: "Patients were allocated randomly to the two groups by opening sealed envelopes on the day of operation."

Comment: Further information was not available.

Blinding of participants and personnel (performance bias)
All outcomes
Unclear risk

Quote: "The intervention assignments were concealed from the patients and the ward nursing staff."

Comment: It was not clear whether the other healthcare providers were blinded.

Blinding of outcome assessment (detection bias)
All outcomes
Unclear risk

Quote: "The intervention assignments were concealed from the patients and the ward nursing staff."

Comment: It was not clear whether the other healthcare providers were blinded.

Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were postrandomisation drop-outs.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear risk

Quote: "This study was supported by grants from Nordjyllands Amts Forskningsrád, Aalborgs Stifts Julelotteri and Det Obelske Familiefond."

Comment: Not clear whether these were the only sources of support.

Larsen 2004

MethodsRandomised clinical trial.
Participants

Country: Denmark.
Number randomised: 50.
Mean age: 49 years.
Females: 18 (36%).

Inclusion criteria:

  1. Elective participants

  2. > 18 years

  3. BMI of 30 or less.

Exclusion criteria:

  1. Acute pancreatitis

  2. Cholecystitis

  3. Cholangitis

  4. Blood diseases

  5. Rheumatic diseases

  6. Acute infectious diseases

  7. Renal diseases

  8. Liver diseases.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 22).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 28).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measure was operating time.
Notes

Withdrawal = 4 because of technical problems with recording echocardiography (in this trial, echocardiographic changes were compared between the groups).

Attempts were made to contact the author in February 2007.

Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Low riskQuote: "The allocation sequence was generated by random numbers".
Allocation concealment (selection bias)Unclear risk

Quote: "Patients were allocated randomly by opening sealed envelopes on the day of operation."

Comment: Further information was not available.

Blinding of participants and personnel (performance bias)
All outcomes
Unclear risk

Quote: "The intervention assignments were unknown to the patients and the nursing staff."

Comment: It was not clear whether the other healthcare providers were blinded.

Blinding of outcome assessment (detection bias)
All outcomes
Unclear risk

Quote: "The intervention assignments were unknown to the patients and the nursing staff."

Comment: It was not clear whether the other healthcare providers were blinded.

Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were postrandomisation drop-outs.
Selective reporting (reporting bias)Low riskComment: All important outcomes were reported.
Vested interest biasUnclear risk

Quote: "This study was supported by funding from Nordjyllands Amts Forskningsraad, Aalborg Stifts Julelotteri and Det Obelske Familefond."

Comment: Not clear whether these were the only sources of support.

Lindgren 1995

MethodsRandomised clinical trial.
Participants

Country: Finland.
Number randomised: 25.
Mean age: 49 years.
Females: 22 (88%).

Inclusion criteria:

  1. Elective cholecystectomy

  2. ASA I or II.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift with or without pneumoperitoneum (pressure not stated) (n = 12).
Group 2: pneumoperitoneum with 12 to 15 mm Hg pressure (n = 13).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measure was operating time.
NotesAttempts were made to contact the author in February 2007 as besides missing data, a conference abstract publication with 24 patients was identified. Reading through the text, we could assume that the published conference abstract had presented data on the same trial. However the conference abstract did not report any outcomes of interest and the inclusion or exclusion of the abstract makes no difference to any of the effect estimates.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Meijer 1997

MethodsRandomised clinical trial.
Participants

Country: Netherlands.
Number randomised: 18.
Mean age: not stated.
Females: 15 (83.3%).

Inclusion criteria:

  1. Elective cholecystectomy

  2. ASA I or II.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift with 5 mm Hg pneumoperitoneum (n = 9 ).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 9).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measures were complications, conversion to open cholecystectomy and operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)Low riskComment: All important outcomes were reported.
Vested interest biasUnclear riskComment: This information was not available.

Ninomiya 1998

MethodsRandomised clinical trial.
Participants

Country: Japan.
Number randomised: 20.
Mean age: 52 years.
Females: 12 (60%).

Inclusion criteria:
1. Laparoscopic cholecystectomy for symptomatic cholelithiasis.

Exclusion criteria:

  1. Choledocholithiasis

  2. Cardiovascular or renal disorders

  3. Serious complications.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 10).
Group 2: pneumoperitoneum with 10 mm Hg pressure (n = 10).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measure was operating time.
NotesAttempts were made to contact the author in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Ortiz-Oshiro 2001

MethodsRandomised clinical trial.
Participants

Country: Spain.
Number randomised: 34.
Mean age: 56 years.
Females: 21 (61.8%).

Inclusion criteria:

  1. Laparoscopic cholecystectomy

  2. ASA I to IV

  3. Treated by the same surgeon and anaesthetist.

Exclusion criteria:

  1. Associated surgical procedures (e.g., hiatal hernia repair, inguinal hernia repair, choledocholithiasis)

  2. Did not complete the pre-operative or postoperative protocol

  3. When surgical findings made the surgeon change the technique (conversion to open surgery, associated surgical procedures)

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 15).
Group 2: pneumoperitoneum with 12 mm Hg pressure (n = 19).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe main outcome measure was operating time.
Notes

Withdrawal, two open cholecystectomy, two open cholecystectomy, four protocol violations.

Attempts were made to contact the author in February 2007.

Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Low riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were postrandomisation drop-outs.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Talwar 2006

MethodsRandomised clinical trial.
Participants

Country: India.
Sample size: 40.
Mean age: 35 years.

Females: 5 (12.5%).
Inclusion criteria:
1.ASA I scheduled for laparoscopic cholecystectomy for symptomatic gallstones.

Exclusion criteria:
1. Patients with liver dysfunction, acute inflammation, cardiopulmonary or metabolic disease, or previous upper abdominal surgery.

Interventions

The participants were randomised to the following groups:
Group 1: abdominal wall lift (n = 20).
Group 2: pneumoperitoneum with 14 mm Hg (n = 20).

Device used for abdominal lift: intra-peritoneal device.

OutcomesThe outcomes reported were complications, conversion to open cholecystectomy, and operating time.
NotesAttempts were made to contact the author in January 2012.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Low risk

Quote: "Selection took place on the day before the surgery using numbered and sealed envelopes."

Comment: Although information about the opacity was not reported, the review authors judge that this was probably performed

Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Low riskComment: There were no postrandomisation drop-outs.
Selective reporting (reporting bias)Low riskComment:  All important outcomes were reported.
Vested interest biasUnclear riskComment: This information was not available.

Tanpravoon 2000

MethodsRandomised clinical trial.
Participants

Country: Thailand.
Number randomised: 84.
Mean age: not stated.

Females: not stated.

Inclusion criteria:
1. Patients with gallstones undergoing laparoscopic cholecystectomy.

InterventionsThe participants were randomised to the following groups:
Group 1: abdominal wall lift (n = not stated).
Group 2: pneumoperitoneum (n = not stated).
Device used for abdominal lift: not stated.
OutcomesThe outcomes reported were operating time and pain.
NotesThe number of participants allocated to each group was not stated. Attempts were made to contact the authors in January 2012.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskComment: This information was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Unclear riskComment: This information was not available.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Uen 2002

MethodsRandomised clinical trial.
Participants

Country: Taiwan.
Number randomised: 95.
Mean age: 48 years.
Females: 66 (69.5%).

Inclusion criteria:

  1. Elective laparoscopic cholecystectomy

  2. ASA I or II

  3. Symptomatic cholecystolithiasis

Exclusion criteria:

  1. Liver dysfunction

  2. Acute inflammation

  3. Cardiopulmonary or metabolic disease

  4. Previous upper abdominal surgery

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 48).
Group 2: pneumoperitoneum with 14 mm Hg pressure (n = 47).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measures were complications, operating time, and hospital stay.
NotesThe authors replied to questions on risk of bias information in March 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskQuote: "The random numbers were generated by rv. uniform function constructed in SPSS statistical software." (author replies)
Allocation concealment (selection bias)Low risk

Quote: "Selection took place on the day before the study using numbered and sealed envelopes".

Comment: Although the information on opacity of the envelope was not available, the review authors judged that this was probably performed.

Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Low riskComment: There were no postrandomisation drop-outs.
Selective reporting (reporting bias)Low riskComment: All important outcomes were reported.
Vested interest biasUnclear riskComment: This information was not available.

Uen 2007

MethodsRandomised clinical trial.
Participants

Country: Taiwan.
Number randomised: 80.
Mean age: 50 years.

Females: 51 (64.6%).

Inclusion criteria:
1. Participants who were classified as ASAI and II.
2. Undergoing elective laparoscopic cholecystectomy for symptomatic gallstones.

Interventions

The participants were randomised to the following groups:
Group 1: abdominal wall lift (n = 40).
Group 2: pneumoperitoneum with 8 mm Hg (n = 39).

Device used for abdominal lift: subcutaneous device.

OutcomesThe outcomes reported were complications and operating time.
NotesOne withdrawal - additional procedure for choledocholithiasis.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Unclear riskQuote: "Patient group allocation took place on the day prior to the study commencing, using randomly distributed, numbered and sealed envelopes."
Comment: Further information about the envelopes was not available.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were post-randomisation drop-outs.
Selective reporting (reporting bias)Low riskComment: All important outcomes were reported.
Vested interest biasUnclear riskComment: This information was not available.

Vezakis 1999

MethodsRandomised clinical trial.
Participants

Country: United Kingdom.
Number randomised: 36.
Mean age: 52 years.
Females: 29 (80.6%).

Inclusion criteria:

  1. Elective laparoscopic cholecystectomy

  2. ASA I or II.

Exclusion criteria:

  1. Extensive upper abdominal incisions

  2. Receiving regular analgesic medication.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 18).
Group 2: pneumoperitoneum with 8 mm Hg pressure (n = 18).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measures were operating time and hospital stay.
Notes

Two cross-over from abdominal wall lift group: 1 because of inadequate exposure; 1 because of necessity to perform laparoscopic CBD exploration.

Attempts were made to contact the author in February 2007.

Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Low riskQuote: "Randomisation was performed preoperatively using envelopes with random numbers."
Allocation concealment (selection bias)Low risk

Quote: "Randomisation was performed preoperatively using envelopes with random numbers."

Comment: further details of the sealed envelope were not available.

Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
High riskComment: There were postrandomisation drop-outs.
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear riskComment: This information was not available.

Yoshida 1997

  1. a

    ASA: American Society of Anesthesiologists

MethodsRandomised clinical trial.
Participants

Country: Japan.
Number randomised: 17.
Mean age: 49 years.
Females: 17 (100%).

Inclusion criteria:
1. Females.

Exclusion criteria:

  1. Common bile duct stone

  2. Liver dysfunction

  3. Acute cholecystitis

  4. Metabolic diseases

  5. Cardiopulmonary disease.

Interventions

Participants were randomly assigned to two groups:

Group 1: abdominal wall lift (n = 8).
Group 2: pneumoperitoneum with 8 mm Hg pressure (n = 9).

Device used for abdominal lift: subcutaneous device.

OutcomesThe main outcome measures were operating time and hospital stay.
NotesThe authors replied to the questions related to postrandomisation drop-outs in February 2007.
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: This information was not available.
Allocation concealment (selection bias)Low riskQuote: "Selection took place on the day before the surgery, using numbered and sealed envelopes".
Comment: Although the information on opacity of the envelope was not available, the review authors judged that this was probably performed.
Blinding of participants and personnel (performance bias)
All outcomes
Unclear riskComment: This information was not available.
Blinding of outcome assessment (detection bias)
All outcomes
Unclear riskComment: This information was not available.
Incomplete outcome data (attrition bias)
All outcomes
Low riskComment: There were no postrandomisation drop-outs (author replies).
Selective reporting (reporting bias)High riskComment: Important outcomes were not reported.
Vested interest biasUnclear risk

Quote: "This work was partially supported by a Grant of Public Trust Fund for the Promotion of Surgery."

Comment: Whether this was the only source of funding was not available.

Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion
Alishahi 2005Comment on an included trial (Larsen 2004).
Giraudo 2001Randomised comparison between two pressures of pneumoperitoneum. Abdominal wall lift was performed in patients with contraindications to pneumoperitoneum.
Jolobe 1997Comment on an included trial (Koivusalo 1996b).
Jugool 2004Comment on an included trial (Larsen 2004).
Kim 2002Although the authors say they have randomised the patients, they state that they tried to match up the patients. Attempts were made to contact the author. There was no reply.
Kurauchi 1999Surgeon's preference was used to determine the allocation.

Ancillary