Background
About 10% to 15% of the adult western population have gallstones. Between 1% and 4% become symptomatic each year. Removal of the gallbladder (cholecystectomy) is the mainstay treatment for symptomatic gallstones. More than half a million cholecystectomies are performed per year in the United States alone. Laparoscopic cholecystectomy (removal of the gallbladder through a keyhole, also known as a port) is now the preferred method of cholecystectomy. While laparoscopic cholecystectomy is generally considered to be less painful than open surgery, pain is one the major reasons for delayed hospital discharge after laparoscopic cholecystectomy. Administration of local anaesthetics (drugs that numb part of the body, similar to the ones used by the dentist to prevent people from feeling pain) into the surgical wound (local anaesthetic wound infiltration) may be an effective way of decreasing pain after laparoscopic cholecystectomy. However, the benefits and harms of local anaesthetic wound infiltration is not known. We sought to answer these questions by reviewing the medical literature and obtaining information from randomised clinical trials on the benefits related to the treatment. When conducted well, such studies provide the most accurate information on the best treatment. We also considered comparative non-randomised studies for treatment-related harms. Two authors searched the literature until February 2013 and obtained information from the studies thereby minimising errors.

Study characteristics
We identified 19 randomised clinical trials in this review. Most participants in the trials were low anaesthetic risk people undergoing planned laparoscopic cholecystectomy.

Key results
A total of 1095 participants were randomised to local anaesthetic wound infiltration (587 participants) or no local anaesthetic wound infiltration (508 participants) in 17 trials. The choice of whether the participants received local anaesthetic agents (or not) was determined by a method similar to the toss of a coin so that the treatments were compared in groups of patients who were as similar as possible. There were no deaths in either group in the seven trials (539 participants) that reported deaths. The difference in serious complications between the groups was imprecise. There were no local anaesthetic-related complications in nearly 450 participants who received local anaesthetic wound infiltration in the different trials that reported complications. None of the trials reported quality of life or the time taken to return to work. The proportion of participants who were discharged as day surgery patients was higher in the local anaesthetic group than in the control group in the only trial that reported this information. The difference in the length of hospital stay or the time taken to return to normal activity was imprecise. Pain was lower in the participants who received intra-abdominal local anaesthetic administration compared with those in the control groups at four to eight hours and at nine to 24 hours, as measured by the visual analogue scale (a chart which rates the amount of pain on a scale of 1 to 10). In the comparisons of different methods of local anaesthetic infiltration, there were differences between the groups in some outcomes but the changes were not consistent. There is, therefore, no evidence to prefer any particular drug or method of administering local anaesthetics. Serious adverse events were rare in studies evaluating local anaesthetic wound infiltration. There is very low quality evidence that infiltration reduces pain in low anaesthetic risk people undergoing elective laparoscopic cholecystectomy. However, the clinical importance of this reduction in pain is likely to be small.

Quality of evidence
Most of the trials were at high risk of bias, that is there is a possibility of arriving at wrong conclusions by overestimating the benefits or underestimating the harms of one method over another because of the way a study was conducted. The overall quality of evidence was very low.

Future research
Further trials are necessary. Such trials should include outcomes such as quality of life, hospital stay, the time taken to return to normal activity, and the time taken to return to work, which are important for the person undergoing laparoscopic cholecystectomy and the people who provide funds for the treatment.