Diverticulitis is the most common cause of colovesical fistula accounting for about 60% of cases. Other causes includes malignancy, Crohn disease, trauma, irradiation and appendicitis. The presence of gas in the urinary bladder in absence of history of Foley catheter insertion or instrumentation and positive presentation of one of the aforementioned causes, the diagnosis of colovesical fistula should be considered. Contrast-enhanced scan is needed for diagnosis either through the bladder (cystogram) or through the rectum (contrast enema) and the fistula can be demonstrated by CT or fluoroscopy.