Appendectomy and subsequent risk of inflammatory bowel diseases

Background. Case-control studies have reported an inverse relationship betw een appendectomy and the risk of ulcerative colitis, but the association ha s not been confirmed in prospective studies. Methods. Using national hospital discharge registry data in Denmark, the au thors followed up 154,434 patients who underwent appendectomy during the pe riod 1977 to 1989 to investigate whether they had subsequent hospitalizatio ns for ulcerative colitis and Crohn's disease. Ratios of observed-to-expect ed first hospitalizations for inflammatory bowel diseases served as measure s of the relative risk (RR). Results. Hospitalization for ulcerative colitis occurred in 84 patients who had appendectomies versus 97.0 expected (RR = 0.87; 95% CI, 0.69-1.09). RR s were not significantly reduced in subgroups defined by sex, age, time sin ce appendectomy, calendar period, or cause of appendectomy. Hospitalization for Crohn's disease occurred in excess (RR = 2.88; 95% CI, 2.45-3.39: n = 150), notably in the first year after appendectomy (RR = 10.83; 95% CI, 8.4 9-13.62; n = 73); but after 5 year, the RR was not significantly elevated. Conclusions. This large population-based cohort study failed to support a s ignificant inverse association between appendectomy and ulcerative colitis risk in the first decade after the operation. The excess of Crohn's disease shortly after appendectomy most likely reflects differential diagnostic pr oblems in patients newly presenting with abandoned pain.