Appendectomy and the risk of developing ulcerative colitis or Crohn's disease: results of a large case-control study. South Limburg Inflammatory Bowel Disease Study Group.

Appendectomy has been pointed out as a protective factor for ulcerative colitis (UC). The aim of this study was to elucidate the role of appendectomy in inflammatory bowel disease (IBD). Prevalent as well as incident cases with IBD were studied separately using a pairwise age- and sex-matched case-control study design. In 232 prevalent UC cases, the risk of developing UC was significantly lower after previous appendectomy (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.15-0.80); subgroup analysis found a protective effect only in pancolitis (OR, 0.2; 95% CI, 0.02-0.7). In 208 patients with Crohn's disease (CD), the OR was not significantly increased but a positive association with appendectomy was observed in ileocecal disease. A significant larger proportion of appendectomies was performed close to the time of diagnosis. Smoking was not a confounding factor. No statistically significant associations were observed in incident IBD patients. Prevalent and incident patients taken together resulted in ORs of 0.44 (95% CI, 0.24-0.78) in UC and 1.65 (95% CI, 0.96-2.91) in CD. An overall protective role of appendectomy for UC was observed. The observations in CD suggest that appendectomy in some cases was a result of still undiagnosed CD.