OBJECTIVES:Previous studies have reported a low prevalence of colon polyps in patients with microscopic colitis. The aim of the study was to test whether such inverse associations applied to other inflammatory diseases of the colon.METHODS:In a case-control study among 130,204 patients undergoing colonoscopy for the work-up of diarrhea, we compared the prevalence of colon polyps in a case population of patients with inflammatory bowel disease (IBD), microscopic colitis, histologic signs of active colitis, diverticulitis, or ischemic colitis, and in a control population with normal colon mucosa. Case and control subjects were compared using odds ratios and their 95% confidence intervals adjusted for age and sex.RESULTS:In 11,176 patients with microscopic colitis, the prevalence of hyperplastic polyps, serrated adenomas, and tubular adenomas were all reduced: odds ratios=0.46 (95% confidence intervals=0.43-0.49), 0.24 (0.19-0.30), and 0.35 (0.33-0.38), respectively. In 4,435 patients with IBD, the corresponding values were: 0.18 (0.15-0.21), 0.24 (0.16-0.35), and 0.18 (0.15-0.21), respectively. In 6,501 patients with histologically active colitis, the corresponding values were: 0.58 (0.53-0.63), 0.57 (0.46-0.70), and 0.63 (0.58-0.68), respectively. No such consistent reduction in polyp prevalence was found in patients with diverticulitis or ischemic colitis.CONCLUSIONS:Chronic inflammatory conditions of the colon are associated with a decreased prevalence of colon polyps.
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