An aberrant, pathological communication between the colon and the bladder.
Comment:
The most common cause of colovesicular fistulas is the sequelae of complicated diverticulitis and accounts for over two-thirds of cases. The second most common cause is a malignancy in 10% to 20% of cases and is usually adenocarcinoma of the colon. Crohn's colitis is the third most common cause (5% to 7% of cases) and usually is a result of long-standing disease.