Population-based study of the need for cholecystectomy after obesity surgery.Plecka Östlund M, Wenger U, Mattsson F, Ebrahim F, Botha A, Lagergren J. Br J Surg. 2012 Mar 7 [Epub ahead of print] BACKGROUND: Weight loss following obesity surgery is associated with gallstone formation, but there is limited evidence on whether prophylactic cholecystectomy is indicated during obesity surgery. The aim of this study was to clarify the need for cholecystectomy following obesity surgery. METHODS: A Swedish nationwide, population-based cohort study was conducted during the 22-year interval 1987-2008. Need for later cholecystectomy for gallstone disease was assessed in patients who had undergone obesity surgery in comparison with the general population of corresponding age, sex and calendar year. This need was also compared with the need for cholecystectomy in cohorts of patients who had undergone antireflux surgery and appendicectomy. Standardized incidence ratios (SIRs) with 95 per cent confidence intervals (c.i.) were calculated to estimate the relative risk.RESULTS: In the obesity surgery cohort of 13 443 patients, the observed number of cholecystectomies (1149, 8·5 per cent) exceeded the expected number by over fivefold (SIR 5·5, 95 per cent c.i. 5·1 to 5·8). The observed need for imperative cholecystectomy (for cholecystitis, cholangitis, pancreatitis, or jaundice; 427, 3·2 per cent) was also greater than expected (SIR 5·2, 4·7 to 5·7). The SIR peaked 7-24 months after obesity surgery and decreased with longer follow-up. The SIRs for cholecystectomy after antireflux surgery and appendicectomy were 2·4 (2·2 to 2·6) and 1·7 (1·6 to 1·7) respectively.CONCLUSION: An increased need for cholecystectomy after obesity surgery was confirmed, but was probably partly due to an increased detection of gallbladder disease only because of the surgery; the individual’s risk of imperative cholecystectomy was low. Therefore, prophylactic cholecystectomy might not be recommended during obesity surgery.