Figure 9b. Sigmoidovesical fistulas as a complication of colonic adenocarcinoma in two patients. (a) Cystogram obtained by using a suprapubic catheter shows opacification of the sigmoid colon (S) and rectum (R) in addition to the bladder (B). The fistula is not clearly seen. (b) Cystogram shows contrast material throughout the large intestine. The contrast material originates at the sigmoid colon, which is contiguous to the bladder at the site of the carcinoma (arrow).