Low frequency of polyps in colonic regions with diverticulosis

Purpose: Conflicting evidence exists regarding any association between diverticulosis and adenomatous polyps. We evaluated the prevalence of polyps and cancer in colonic regions containing diverticula. Methods: Six hundred consecutive colonoscopy reports from a single endoscopist were reviewed to determine prevalence and location of diverticulosis and polyps. Additionally, pathology reports of 88 colon cancer resection specimens were reviewed for the presence of diverticulosis, and compared with expected prevalence of diverticulosis in that colonic region based on the collected colonoscopy data. Results: Overall, rates of detected polyps were comparable between patients with and without diverticulosis. However, analyzing the data by colonic segment containing diverticulosis, the prevalence of adenomatous polyps was reduced in regions of diverticulosis compared to the same colonic segment unaffected by diverticulosis (7 vs. 17% for rectosigmoid (p = 0.005); 5 vs. 18% for descending (p < 0.0001); and 17 vs. 27% for ascending colon (p = 0.0495)). Among colon cancer resection specimens, the prevalence of diverticulosis was significantly reduced in the rectosigmoid and ascending colon, compared with expected rates of diverticulosis in those regions. (13 vs. 42% in rectosigmoid (p = 0.0006); 3 vs. 17% in ascending colon (p = 0.043)). Conclusion: Despite similar overall frequency of polyps in patients with and without diverticulosis, polyps were significantly less likely in the colonic segment affected by diverticulosis. Additionally, the frequency of diverticulosis in areas of cancer in the rectosigmoid and ascending colon was significantly lower than expected compared with the expected frequency of diverticulosis for those colonic regions. These observations suggest a true negative association between colonic neoplasia and diverticulosis.