| Figure 1. Study flow diagram. |
| 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. |
| 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. |
| 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. |
| 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 (D^{2}) 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. |
| 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. |
| 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. |
| 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. |
| 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 (D^{2}) 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. |
| 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). |
| Analysis 1.1. Comparison 1 Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, Outcome 1 Mortality. |
| 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. |
| Analysis 1.4. Comparison 1 Abdominal wall lift with pneumoperitoneum versus pneumoperitoneum, Outcome 4 Operating time. |
| Analysis 2.1. Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 1 Mortality. |
| 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). |
| Analysis 2.7. Comparison 2 Abdominal wall lift without pneumoperitoneum (AWL) versus pneumoperitoneum (PP), Outcome 7 Proportion discharged as day-patient laparoscopic cholecystectomy. |
| 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. |