A parastomal hernia is a type of incisional hernia that occurs in relation to a previously constructed stoma. Most develop within the first few years after construction of the stoma, but they can occur up to 20 years afterwards (Londono-Schimmer 1994; Carne 2003). Parastomal herniation remains a relatively common complication amongst stoma patients, with reported incidences between 2 and 56 per cent, depending on the type of stoma and the length of follow-up (Cheung 2001; Carne 2003; Shabbir 2010). Although many parastomal hernias remain asymptomatic (Pearl 1989), they can be a considerable cause of patient morbidity, with up to a third requiring surgical intervention for complications such as pain, bowel obstruction and fistulation (Janes 2004; Janes 2009; Wara 2011).
Once a parastomal hernia has become established, it may be repaired surgically by an open or a laparoscopic approach (Israelsson 2008; Hansson 2009; Lopez-Cano 2009; Pastor 2009). Open surgical techniques include relocation of the stoma, direct repair of the fascial defect and repair using a prosthetic mesh. Results to date when these techniques are used have been disappointing, with reported recurrence rates of 30 to 76 per cent (Burns 1970; Kronborg 1974; Sjodahl 1988; Williams 1990; Rubin 1994; Martin 1996; Amin 2001; Hansson 2009); research is ongoing (NCT00771407). Although short-term results of laparoscopic repair appear promising, with reported recurrence rates less than 2 per cent (Hansson 2009), patient selection remains an issue, and those who have extensive intra-abdominal adhesions are not well suited to laparoscopic repair (Pilgrim 2010).
Because of the frequency of parastomal herniation and the relatively limited success of repair, attention has been focused on preventing parastomal herniation at the outset－at the time of stoma formation. Techniques such as placement of the stoma through the rectus abdominis have traditionally been thought to reduce the incidence of herniation (Eldrup 1982; Sjodahl 1988; Stephenson 2010) and are often performed routinely. In recent times, mesh reinforcement of the stoma has been advocated to further decrease the incidence of hernia formation (Janes 2004; Janes 2004a; Hammond 2008; Janes 2009; Serra-Aracil 2009; Ellis 2010), although safety concerns persist regarding the use of prosthetics in a contaminated surgical field (Tam 2010).
Description of the condition
A parastomal hernia is a type of incisional hernia that occurs in relation to a previously constructed stoma. Development of a parastomal hernia remains a relatively common occurrence within colorectal surgery, with incidences as high as 56 per cent (Cheung 2001; Carne 2003; Shabbir 2010). Although many remain asymptomatic, presenting symptoms range from unacceptable cosmesis and poorly fitting stoma devices to bowel strangulation, ischaemia and obstruction (Carne 2003). Repair rates of around 30 per cent are variable (Carne 2003; Israelsson 2005; Tam 2010), and repair is associated with its own risk of morbidity. Cost-analysis has shown that the repair itself can be expensive despite continued high recurrence rates after surgical repair (Carne 2003; Israelsson 2005; Tam 2010).
Description of the intervention
A prosthetic mesh is placed surgically at the time of stoma formation, circumferentially adjacent to the stoma, and is secured to one of the fascial layers of the abdominal wall. The level at which the mesh is placed and secured can vary between intraperitoneal, preperitoneal and subcutaneous approaches, with the mesh inserted and secured locally at the time of stoma formation via an open (Janes 2004; Janes 2004a; Hammond 2008; Janes 2009; Serra-Aracil 2009; Ellis 2010) or a laparoscopic technique (Lopez-Cano 2009; Lopez-Cano 2013). The material used may vary; both prosthetic (Vijayasekar 2008) and biological/composite (Wijeyekoon 2010) types of mesh have been described.
How the intervention might work
A prosthetic mesh placed at the time of stoma formation may act as a mechanical buttress, strengthening the abdominal wall at a site of potential weakness, thus preventing future hernia formation. Studies have shown that placement of such a mesh may reduce the incidence of parastomal herniation (Hammond 2008; Janes 2009; Serra-Aracil 2009; Tam 2010). Mesh placement at the time of index surgery has been considered relatively safe, with complication rates of < 5 per cent (Tam 2010).
Why it is important to do this review
In colorectal surgery, stomas are often constructed on a temporary basis, sometimes to protect a downstream colorectal anastomosis, with future reversal intended. Indications for permanent stoma formation persist, however, in individuals with cancer (i.e. abdominoperineal excision of the rectum), inflammatory bowel (e.g. total colectomy) and functional bowel surgery. Some patients, many of whom are young, are required to live a significant proportion of their lives with a permanent stoma.
Parastomal herniation often leads to significant lifetime morbidity; therefore, the current emphasis on prevention is particularly important, as traditional revision surgery (aponeurotic repair or relocation) rarely offers a robust long-term solution, and associated recurrence rates are greater than 30 per cent (Tekkis 1999).
Mesh reinforcement of stomas to prevent parastomal herniation seems to be an intuitive way to address this problem and has been advocated in several observational studies (Israelsson 2005; Gogenur 2006; Marimuthu 2006; Berger 2008; Vijayasekar 2008). Nevertheless, the uptake of this technique has been limited to date. Despite current evidence, the perceived lack of robustness of observational studies and uncertainty regarding the applicability of results from small cohorts may have contributed to lack of dissemination of the technique. A meta-analysis of data from available randomised controlled trials would improve the precision of any beneficial treatment effect and would enhance the power of studies to identify adverse outcomes associated with this procedure.
The overall objective of this review is to evaluate whether mesh reinforcement of abdominal wall stomas affects the incidence of parastomal herniation without affecting mortality. More specific objectives for review include the following.
- Is mesh placement more effective in preventing parastomal herniation for certain stoma types (e.g. end vs loop, ileostomy vs colostomy)?
- Does mesh placement affect the incidence of surgical intervention for adverse symptoms related to parastomal hernia formation?
- Does mesh placement have an effect on total operative time or length of hospital stay?
- What is the incidence of mesh-specific complications (i.e. stoma aperture stenosis/stricture, intestinal fistulation, mesh-related infection (with/without reoperation) and mortality)?
- Does mesh placement have an influence on patient-reported symptoms and postoperative quality of life (i.e. difficulty with bag application, leakage of stoma bag contents, nausea, vomiting, abdominal bloating and parastomal discomfort)?
- What is the impact of the intervention on rehospitalisation/ambulatory visits required for parastomal hernia problems/treatment?
Criteria for considering studies for this review
Types of studies
Only randomised controlled trials (RCTs) of parallel design, irrespective of blinding, sample size, publication status or language, will be included. Quasi-randomised studies and other study designs in the presence of RCTs will be excluded because of the potential for bias (Gurusamy 2009; Higgins 2011).
Types of participants
All individuals receiving a permanent or a temporary abdominal wall stoma for colorectal (ileostomy or colostomy) or urological (urostomy) reasons in elective and emergency settings will be included, regardless of the underlying indication for surgery.
Types of interventions
Any form of mesh reinforcement of the stoma site at the index operation will be considered, regardless of type of mesh, type of stoma, anatomical plane of placement, and experience of the operating surgeon.
Types of outcome measures
- Overall incidence of parastomal herniation with and without placement of parastomal mesh support at the time of the index operation
- Incidence of parastomal herniation (defined as above) by stoma type (e.g. end vs loop, ileostomy vs colostomy)
- Incidence of surgical intervention for adverse symptoms related to parastomal hernia formation
- Operative time for index operation
- Postoperative length of hospital stay
- Mesh-specific complications (i.e. stoma aperture stenosis/stricture, intestinal fistulation, mesh-related infection (with/without reoperation) and mortality)
- Patient-reported symptoms and postoperative quality of life (i.e. difficulty with bag application, leakage of stoma bag contents, nausea, vomiting, abdominal bloating and parastomal discomfort)
- Number of rehospitalisations/ambulatory visits required for parastomal hernia problems/treatment.
Search methods for identification of studies
The first reference to parastomal herniation in the literature appeared in 1974 (Lynne 1974), hence searches will be commenced from 1970 onwards.
We will search:
- the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library; latest version);
- MEDLINE (Ovid; 1970 to date);
- EMBASE (Ovid; 1974 to date); and
- Science Citation Index Expanded (1970 to date).
No limitations based on language were applied. For comprehensive search strategies, see Appendix 1 (CENTRAL), Appendix 2 (MEDLINE), Appendix 3 (EMBASE) and Appendix 4 (Science Citation Index Expanded).
Searching other resources
We will search the references of identified trials for further relevant trials. We will also search the metaRegister of Controlled Trials (mRCT). This register includes the ISRCTN Register and the NIH ClinicalTrials.gov Register, among others.
Data collection and analysis
Selection of studies
James Cragg (JC) and Huw Jones (HJ) will independently identify the trials for inclusion. Excluded trials and reasons for exclusion will be listed.
Data extraction and management
James Cragg (JC) and Huw Jones (HJ) will independently extract data for the review. In addition to outcomes, population characteristics (such as sex, age and disease etiology) and interventions used in each trial will be evaluated. We will independently assess the methodological quality of the trials, without masking of trial names. Differences in opinion will be resolved through discussion, with the final decision resting with the senior review author.
Assessment of risk of bias in included studies
The methodological quality of trials regarding sequence generation; allocation concealment; blinding of participants, personnel and outcome assessors; incomplete outcome data; selective outcome reporting; and other sources of bias (as described below) will be assessed (Gurusamy 2009; Higgins 2011).
• Low risk of bias (the method used is adequate (e.g. computer-generated random numbers, table of random numbers) or is unlikely to introduce confounding)
• Uncertain risk of bias (information is insufficient to permit assessment of whether the method used is likely to introduce confounding)
• High risk of bias (the method used (e.g. quasi-randomised trials) is improper and is likely to introduce confounding)
• Low risk of bias (the method used (e.g. central allocation) is unlikely to induce bias on the final observed effect)
• Uncertain risk of bias (information is insufficient to permit assessment of whether the method used is likely to induce bias on the estimate of effect)
• High risk of bias (the method used (e.g. open random allocation schedule) is likely to induce bias on the final observed effect)
Blinding of participants and outcome assessors
It is impossible to blind surgeons as to whether mesh reinforcement was performed. However, it is possible to blind participants and outcome assessors to the groups.
• Low risk of bias (blinding was performed adequately, or the outcome measurement is not likely to be influenced by lack of blinding)
• Uncertain risk of bias (information is insufficient to permit assessment of whether the type of blinding used is likely to induce bias on the estimate of effect)
• High risk of bias (no blinding or incomplete blinding, and the outcome or the outcome measurement is likely to be influenced by lack of blinding)
Incomplete outcome data
• Low risk of bias (underlying reasons for loss of data are unlikely to make treatment effects depart from plausible values, or proper methods have been employed to handle missing data)
• Uncertain risk of bias (information is insufficient to permit assessment of whether the missing data mechanism in combination with the method used to handle missing data is likely to induce bias
on the estimate of effect)
• High risk of bias (the crude estimate of effects (e.g. complete case estimate) will clearly be biased because of underlying reasons for the loss of data, and the methods used to handle missing data are unsatisfactory)
Selective outcome reporting
• Low risk of bias (the trial protocol is available, and all prespecified outcomes that are of interest for the review have been reported or are similar)
• Uncertain risk of bias (information is insufficient to permit assessment of whether the magnitude and direction of the observed effect are related to selective outcome reporting)
• High risk of bias (not all of the trial’s prespecified primary outcomes have been reported or are similar)
• Low risk of bias (sample size calculation was reported and the trial was not stopped, or the trial was stopped early by a formal stopping rule at a point where the likelihood of observing an extreme intervention effect due to chance was low)
• Uncertain risk of bias (sample size calculations were not reported, and it is not clear whether the trial was stopped early
• High risk of bias (the trial was stopped early because of an informal stopping rule, or the trial was stopped early by a formal stopping rule at a point where the likelihood of observing an extreme intervention effect due to chance was high)
• Low risk of bias (adequate level of standardisation of technique/level of surgeon experience/number)
• Uncertain risk of bias (level of standardisation of technique/level of surgeon experience/number not explicitly stated)
• High risk of bias (considerable variation in the level of standardisation of technique/level of surgeon experience/number)
Measures of treatment effect
For dichotomous variables, the risk ratio (RR) will be calculated with 95 per cent confidence intervals (CIs).
Unit of analysis issues
The unit of analysis will be each participant recruited into the trials.
Dealing with missing data
An intention-to-treat analysis will be followed (Newell 1992).
Assessment of heterogeneity
Assessment of reporting biases
A funnel plot will be used to explore bias by assessing asymmetry in the funnel plot of trial size
against treatment effect (Egger 1997).
Meta-analyses will be performed according to the recommendations of The Cochrane Collaboration (Higgins 2011) using the software package Revman 5.2. A random-effects model (DerSimonian 1986) will be used (the random-effects model is perceived to be superior in that it better incorporates between-study variability in the presence of heterogeneity, thus encouraging more conservative interpretation (Higgins 2011)).
Subgroup analysis and investigation of heterogeneity
The following subgroup analysis is planned, and the Chi
value of 0.05 will be used to identify subgroup differences.
- Parastomal herniation and the incidence of parastomal herniation requiring surgical repair with mesh reinforcement versus conventional stoma formation for 'loop' versus 'end' stomas.
A sensitivity analysis will be performed by imputing missing values using various scenarios such as good outcome analysis, poor outcome analysis, best case analysis and worst case analysis
Thanks to Professor Norman S Williams, MS, FRCS, FMedSci, and Wijeyekoon SP, Gurusamy K, El-Gendy K and Chan CL for allowing us use their protocol as a template.
Appendix 1. CENTRAL
#1 MeSH descriptor: [Enterostomy] explode all trees
#2 MeSH descriptor: [Surgical Stomas] explode all trees
#3 (colostom* or ileostom* or enterostom* or stom* or ostom* or parastom*):ti,ab,kw
#4 (#1 or #2 or #3)
#5 MeSH descriptor: [Hernia, Abdominal] explode all trees
#7 (#5 or #6)
#8 MeSH descriptor: [Surgical Mesh] explode all trees
#9 MeSH descriptor: [Prosthesis Implantation] explode all trees
#10 MeSH descriptor: [Absorbable Implants] explode all trees
#11 MeSH descriptor: [Bioprosthesis] explode all trees
#12 (mesh* or prosthesis* or implant*):ti,ab,kw
#13 (#8 or #9 or #10 or #11 or #12)
#14 (#4 and #7 and #13)
Appendix 2. MEDLINE (Ovid)
1. exp Enterostomy/
2. exp Surgical Stomas/
3. (colostom* or ileostom* or enterostom* or stom* or ostom* or parastom*).mp.
4. 1 or 2 or 3
5. exp Hernia, Abdominal/
7. 5 or 6
8. exp Surgical Mesh/
9. exp Prosthesis Implantation/
10. exp Absorbable Implants/
11. exp Bioprosthesis/
12. (mesh* or prosthesis* or implant*).mp.
13. 8 or 9 or 10 or 11 or 12
14. 4 and 7 and 13
15. randomized controlled trial.pt.
16. controlled clinical trial.pt.
19. clinical trial.sh.
22. 15 or 16 or 17 or 18 or 19 or 20 or 21
24. 22 and 23
25. 14 and 24
26. limit 25 to yr="1970 -Current"
Appendix 3. EMBASE (Ovid)
1. exp enterostomy/
2. *colon pouch/
3. *stoma bag/
4. (colostom* or ileostom* or enterostom* or stom* or ostom* or parastom*).m_titl.
5. 1 or 2 or 3 or 4
6. exp hernia/
8. 6 or 7
9. exp surgical mesh/
12. (mesh* or prosthesis* or implant*).m_titl.
13. 9 or 10 or 11 or 12
14. 5 and 8 and 13
15. randomized controlled trial/
17. controlled study/
18. multicenter study/
19. phase 3 clinical trial/
20. phase 4 clinical trial/
21. double blind procedure/
22. single blind procedure/
23. ((singl* or doubl* or trebl* or tripl*) adj (blind* or mask*)).ti,ab.
24. (random* or cross* over* or factorial* or placebo* or volunteer*).ti,ab.
25. 20 or 17 or 21 or 23 or 16 or 22 or 18 or 15 or 24 or 19
27. (animal* or nonhuman*).ti,ab.
28. 27 and 26
29. 27 not 28
30. 25 not 29
31. 14 and 30
Appendix 4. Science Citation Index Expanded
#1 Topic=(colostom* or ileostom* or enterostom* or stom* or ostom* or parastom*)
#3 Topic=(mesh* or prosthesis* or implant*)
#4 Topic=(random* OR controlled OR RCT OR placebo OR trial OR group* OR trial*)
#5 (#1 AND #2 AND #3 AND #4)
Contributions of authors
Data extraction and analysis (JC, HJ and Michael Rees (MR)).
Manuscript preparation (all review authors named in the byline).
Declarations of interest
The review authors declare that all analyses and interpretations reflect their opinions; no company was involved in analysis
or interpretation of data, or in the writing of this systematic review.
Sources of support
- None, Not specified.
- None, Not specified.