Intramesenteric penetration is relatively uncommon. As far as we know, only 13 cases, including the present one, have been reported in the world.
A 75-year-old woman was seen at our hospital because of lower abdominal pain and nausea. She had been told that she had diverticulum of the sigmoid colon. After examination, she went home, but the next day she came again because her abdominal pain had not improved. When she was admitted, WBC was 24, 300/mm³ and CRP was 20.0mg/dl. An abdominal CT scan revealed a large tumor in the pelvic cavity which contained a good deal of air. A barium enema study showed that contrast medium had leaked out of the intestine and contrasted like a tumor. Suspecting penetration of the sigmoid colon by the diverticulitis, so we performed laparotomy. Much stool was contained in the sigmoid mesentry, so we resected the sigmoid colon and performed end-to-end anastomosis. Histological diagnosis of the resected specimen material was penetration by diverticulitis.