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.

BACKGROUND & AIMS: 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).
METHODS: Prevalent as well as incident cases with IBD were studied separately using a pairwise age- and sex-matched case-control study design.
RESULTS: 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.
CONCLUSIONS: 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.