Ans. D. Colovesical fistulaUlcerative colitisa. Inflammatory bowel diseaseb. Rectum is always involvedc. Bloody diarrhea is the most common presentationDouble Contrast Barium Enema (DCBE) is the radiological examination of choice to show disease extent and severityInstant enema - In UC the large bowel is inflamed and contains no fecal matter, and hence enema study can be done without bowel preparation.Acute changes:a. Earliest radiological change on DCBE is blurring of mucosal lining and a fine mucosal granularity (enface) due to edema.b. Colorectal narrowing and incomplete filling due to spasm and irritabilityc. Scalloping of the edges of colon, especially the sigmoid colond. Mucosal stippling due to crypt abscesses (continuous; not transmural)e. 'Collar button' ulcersf. Toxic megacolong. PseudopolypsChronic changes:a. Shortening and narrowing of colonb. 'Lead pipe' colonc. Loss of haustrationd. Backwash ileitise. Thickened rectal valvef. Widening of Presacral space (normally 1.5cm at S_4 vertebral level)g. Benign strictureh. Carcinoma of colon/rectum