Appendectomy and the development of ulcerative colitis: results of a metaanalysis of published case-control studies

Numerous epidemiological studies have been performed to determine risk factors that might contribute to the development of ulcerative colitis (UC). Recent studies have focused on the role of appendectomy in the disease's pathogenesis. This report aims to review and analyze the degree of evidence from recent published studies.

Medline and Embase databases were scrutinized for studies published between 1987 and January 1999. Reference lists from published articles, reviews, and abstracts from major gastrointestinal (GI) meetings were also reviewed. All studies specifically designed to evaluate the association between appendectomy and UC were selected. Thirteen studies that satisfied our selection criteria were evaluated by metaanalysis.

The 13 case-control studies collectively gathered evidence from 2770 patients with UC and 3352 controls. Combining the results of the individual studies gave an overall odds ratio of 0.307 (95% confidence interval [CI] = 0.249-0.377) in favor of appendectomy (p<0.0001). This suggests that appendectomy gives a 69% reduction in the risk of developing UC (95% CI = 62%-75%). The test for heterogeneity (of all 13 studies) was not significant (chi2 = 16.213, d.f. = 12, p>0.10). The influence of potential confounding factors (mainly smoking) on these results could be excluded.

The review of the literature and the metaanalysis of the selected studies suggest that the inverse association between appendectomy and UC is strong and consistent. Further studies are needed to establish whether a causal relationship exists.