This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Radiology
[{'content': "Pipe stem colon on barium enema is seen with: \nSelect and explain. \nA. Crohn's disease, B. Ulcerative colitis, C. Ischemic colitis, D. Amoebic colitis", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Ulcerative colitisBarium Enema Findings in Ulcerative Colitis:* Earliest finding on air-contrast Barium enema is loss of and fine mucosal granularity.* Pseudo-polyps which are scattered islands of edematous mucosa in vast expanse of ulcerated mucosa* Double-tracking-tong, longitudinal ulcers in submucosa* Bowel margins appear spicule like from tiny, multiple ulcerations* Collar button ulcers- rom undermining* Shortening of the colon-may be from spasm of longitudinal muscles or from irreversible fibrosis (lead- pipe colon/pipe stem colon)* Loss of haustration on left side of colon.', 'role': 'assistant'}]