Risk of colon cancer after computed tomography-diagnosed acute diverticulitis: is routine colonoscopy necessary?

Current guidelines recommend computed tomography (CT) for diagnosing diverticulitis and for routine follow-up colonoscopy to rule out cancer. Scientific data to support routine colonoscopy after acute diverticulitis are scarce and conflicting. This study aimed to evaluate the risk of colon cancer mimicking diverticulitis, and hence the need for routine colonoscopy after CT-diagnosed acute diverticulitis. This study was a retrospective analysis of patients treated for acute diverticulitis in a single academic institution during 2006-2010. Data regarding age, sex, laboratory parameters, prior diverticulitis, surgical operations, pathology reports, and CT characteristics were collected. Risk factors for finding colon cancer after CT-diagnosed acute diverticulitis were identified by multivariate analysis. The study enrolled 633 patients with CT-diagnosed acute diverticulitis. Of these patients, 97 underwent emergency resection, whereas 536 were treated conservatively, 394 of whom underwent colonoscopy. The findings showed 17 cancers (2.7 %) in patients with an initial diagnosis of acute diverticulitis. As shown by CT, 16 cancer patients (94 %) had abscess, whereas one patient had pericolic extraluminal air but no abscess. Of the patients with abscess, 11.4 % had cancer mimicking acute diverticulitis. No cancer was found in the patients with uncomplicated diverticulitis. Besides abscess, other independent risk factors for cancer included suspicion of cancer by a radiologist, thickness of the bowel wall exceeding 15 mm, no diverticula observed, and previously undiagnosed metastases. Routine colonoscopy after CT-proven uncomplicated diverticulitis seems to be unnecessary, but colonoscopy should be performed for patients with a diagnosis of diverticular abscess.