Abstract: A total of 1092 participants randomly assigned to the low pressure group (509 participants) and the standard pressure group (583 participants) in 21 trials provided information for this review on one or more outcomes. Three additional trials comparing low pressure pneumoperitoneum with standard pressure pneumoperitoneum (including 179 participants) provided no information for this review. Most of the trials included low anaesthetic risk participants undergoing elective laparoscopic cholecystectomy. One trial including 140 participants was at low risk of bias. The remaining 20 trials were at high risk of bias. The overall quality of evidence was low or very low. No mortality was reported in either the low pressure group (0/199; 0%) or the standard pressure group (0/235; 0%) in eight trials that reported mortality. One participant experienced the outcome of serious adverse events (low pressure group 1/179, 0.6%; standard pressure group 0/215, 0%; seven trials; 394 participants; RR 3.00; 95% CI 0.14 to 65.90; very low quality evidence). Quality of life, return to normal activity, and return to work were not reported in any of the trials. The difference between groups in the conversion to open cholecystectomy was imprecise (low pressure group 2/269, adjusted proportion 0.8%; standard pressure group 2/287, 0.7%; 10 trials; 556 participants; RR 1.18; 95% CI 0.29 to 4.72; very low quality evidence) and was compatible with an increase, a decrease, or no difference in the proportion of conversion to open cholecystectomy due to low pressure pneumoperitoneum. No difference in the length of hospital stay was reported between the groups (five trials; 415 participants; MD -0.30 days; 95% CI -0.63 to 0.02; low quality evidence). Operating time was about two minutes longer in the low pressure group than in the standard pressure group (19 trials; 990 participants; MD 1.51 minutes; 95% CI 0.07 to 2.94; very low quality evidence). Laparoscopic cholecystectomy can be completed successfully using low pressure in approximately 90% of people undergoing laparoscopic cholecystectomy. However, no evidence is currently available to support the use of low pressure pneumoperitoneum in low anaesthetic risk patients undergoing elective laparoscopic cholecystectomy. The safety of low pressure pneumoperitoneum has to be established. Further well-designed trials are necessary, particularly in people with cardiopulmonary disorders who undergo laparoscopic cholecystectomy.

Plain-language summary: A total of 1092 patients were studied in 21 trials. Patients were assigned to a low pressure group (509 patients) or a standard pressure group (583 patients). The choice of treatment was determined by a method similar to the toss of a coin. Most of the trials included low surgical risk patients undergoing planned laparoscopic cholecystectomy. Laparoscopic cholecystectomy could be completed successfully using low pressure in approximately 90% of people undergoing this procedure. No deaths were reported in either low pressure or standard pressure groups in eight trials that reported deaths (total of 434 patients in both groups). Seven trials with 394 patients described complications related to surgery. One participant experienced the outcome of serious adverse events (low pressure group 1/179, 0.6%; standard pressure group 0/215, 0%). Quality of life, return to normal activity, and return to work were not reported in any of the trials. The difference in the percentage of people undergoing conversion to open operation (from key-hole operation) between the low pressure group (2/269; 0.8%) and the standard pressure group (2/287; 0.7%) was imprecise. This was reported in 10 studies. No difference was noted in the length of hospital stay between the groups. Operating time was about two minutes longer (very low quality evidence) in the low pressure group than in the standard pressure group. Currently no evidence is available to support the use of low pressure pneumoperitoneum in low surgical risk patients undergoing planned laparoscopic cholecystectomy. The safety of low pressure pneumoperitoneum has to be established. Only one trial including 140 participants was at low risk of bias (low chance of arriving at wrong conclusions because of study design). The remaining 20 trials were at high risk of bias (high chance of arriving at wrong conclusions because of trial design). The overall quality of evidence was very low. Further well-designed trials are necessary, particularly in high surgical risk patients undergoing laparoscopic cholecystectomy.