Abstract
Recently, we experienced a case of acute appendicitis with mesenterium commune. A 25-year-old man, who had mental retardation, was emergently operated on under a diagnosis of acute abdomen of unknown origin. The intra-operative diagnosis was acute panperitonitis due to gangrenous appendicitis with mesenterium commune. Appendectomy and irrigation drainage were performed. The postoperative course was uneventful, and the patient was discharged on the postoperative day 15. In the circumstances of acute abdomen, it might be useful to take the coexistence of intestinal malrotation like mesenterium commune into consideration.