A 25-year-old-woman with four years history of pancolonic ulcerative colitis (UC) underwent laparoscopy-assisted restorative proctocolectomy. She developed postoperatively abdominal pain, high fever, bloody diarrhea. Computed tomography showed thickening of duodenal and small intestinal wall, and endoscopic examination revealed diffuse mucosal edema, redness, erosion and ulceration involving duodenum, small intestine and ileal pouch that was similar in appearance to UC. She experienced massive melena five times and was successfully treated by transcatheter arterial embolization. Some antibiotics and prednisolone failed to decrease activity of the lesion but the symptoms and endoscopic findings improved since intravenous dexamethasone injection.