A middle aged male presented to the emergency room with acute abdominal pain. CECT revealed sigmoid diverticulitis. A focus of air was also seen within the bladder. 3D reformatted images demonstrated a fistulous connection between the sigmoid colon and bladder (best seen on the second and third images above). The diagnosis of colovesicular fistula was made.
Colovesical fistulas arise most often in the setting of diverticular disease. Findings that suggest fistula formation on CT include intravesical air, bladder wall thickening and perivesicular inflammatory changes. The precise fistulous connection is not always visualized.
In addition to diverticulitis, colovesicular fistulas can occur in the setting of inflammatory bowel disease, gastrointestinal or genitourinary neoplasms, radiation therapy, pelvic surgery, and foreign body impaction.
Yu NC, Raman SS, Patel M, et al. Fistulas of the genitourinary tract: a radiologic review. Radiographics 2004;24:1331-52.