This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inflammatory bowel disease, Subject name: Surgery
[{'content': 'In ulcerative colitis, after colectomy least likely to resolve is: \nSelect and explain. \nA. Ankylosing spondylitis, B. PSC, C. Pyoderma gangrenosum, D. Erythema nodosum', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Extraintestinal Manifestations of Ulcerative Colitis Ahritis Ankylosing spondylitis Erythema nodosum Pyoderma gengrenosum Primary sclerosing cholangitis (PSC) Colectomy has no effect on the course of PSC in UC. Pyoderma gangrenosum is more common in UC. MC cutaneous manifestation of IBD: Erythema nodosum Erythema nodosum is the most responsive to treatment of the bowel and persistence of the lesion indicates inadequate control of IBD.', 'role': 'assistant'}]