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: Medicine
[{'content': 'The operation of choice in ulcerative colitis \nSelect and explain. \nA. Proctocolectomy with ileoanal anastomosis, B. Subtotal colectomy and ileostomy, C. Proctocolectomy and permanent end ileostomy, D. Subtotal colectomy and ileorectal anastomosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The operation of choice in ulcerative colitis is proctocolectomy (with preservation of the anal sphincter complex) with ileoanal J pouch anastomosis (IPAA).Total proctocolectomy has the advantage of removing all diseased mucosa, thereby preventing fuher inflammation and the potential for progression to dysplasia or carcinoma. ie; Total colon and rectum are removed, ileal pouch is constructed (to function like rectum) and anastomosed to the anal canalRef: Sabiston 20e pg: 1372, Harrison 19e pg: 1962', 'role': 'assistant'}]