Colovesical fistulas are difficult to visualize. However, CT is sensitive for the detection of air in the bladder, which, in the absence of previous bladder catheterization or cystoscopy, is virtually diagnostic of an enterovesical fistula. The detection of bladder wall thickening adjacent to an area of diverticulitis supports the diagnosis. Cystoscopy frequently reveals focal mucosal inflammation in the area of the fistula, and contrast cystography may opacify the fistula. Barium enema often fails to opacify a colovesical fistula, although secondary changes of diverticulitis are often apparent.
Colonoscopy is necessary to exclude colon cancer and inflammatory bowel disease.
CT, cystoscopy, barium enema, and colonoscopy are complementary studies for the evaluation of suspected colovesical fistula. Patients with a fistula caused by diverticulitis should have elective surgical resection of the involved segment of colon when the acute inflammatory process has been controlled. In colovesical fistulas, the adherent colon can usually be dissected off the bladder and resected. The bladder defect is oversewn. It usually occurs after repeated episodes of diverticulitis but may be the initial manifestation.