Protective effect of appendectomy on the development of ulcerative colitis - Matched, case-control study

PURPOSE: Appendectomy and cigarette smoking have been suggested to reduce the chance of developing ulcerative colitis. A case-control study was undertaken to determine the relative incidence of appendectomy in patients with ulcerative colitis. METHODS: This case-control study examined the incidence of appendectomy in patients with ulcerative colitis and patients attending an orthopedic outpatient clinic. RESULTS: Of 100 patients with ulcerative colitis, 75 pairs were matched for age, gender, and cigarette smoking. The ulcerative colitis group had an appendectomy rate of 8 percent (6/75), compared with 21 percent in the control group (P = 0.018). The odds ratio was 3.5 (95 percent confidence interval, 1.15-10.6). CONCLUSIONS: No previous study has examined the effect of appendectomy, controlling for cigarette smoking. This study confirms that appendectomy protects against or reduces the chance of development of ulcerative colitis. A possible immunological explanation for this effect is advanced.