Low Prevalence of Colon Polyps in Chronic Inflammatory Conditions of the Colon

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.