- OBJECTIVE: Appendectomy was shown to be protective in patients with ulcerative colitis (UC). There are fewer data in Crohn's disease (CD). Other operations were less studied. The aim of this study was to investigate the prevalence of appendectomy, cholecystectomy, and tonsillectomy, including their timing, in patients with inflammatory bowel disease in comparison to controls. METHODS: Two hundred seventy-one patients with UC and 260 with CD, 475 clinic controls, and 428 community controls were interviewed. RESULTS: Appendectomy was found in 5.5% patients with UC, in 11% of clinic controls (p < 0.05), and 7.7% of community controls (p = not significant). The differences were more significant for appendectomy before onset of disease. Appendectomy was performed in 19.2% of patients with CD, in 10.9% of clinic controls, and in 10.1% of community controls (p < 0.01). However, there were no significant differences when only appendectomy before onset of disease was considered. Cholecystectomy was found in 1.5% of patients with UC, in 6.1% of clinic controls (p < 0.01), and in 4.5% of community controls (p = not significant). The difference remained significant when confined to operations performed before disease onset. No such difference was found in patients with CD. No significant difference was found in the prevalence of tonsillectomy between patients and controls. CONCLUSIONS: Appendectomy is protective in UC; it is more frequent, but not a risk factor in CD. The role of cholecystectomy should be investigated further.