Abstract
A 68-year-old man complained of abdominal pain and went into shock. Abdominal computed tomography revealed the presence of a large, low-density mass located in the left retroperitoneal space. Hematologic examination revealed anemia; abdominal paracentesis demonstrated the presence of blood. A clinical diagnosis of hemorrhage due to the rupture of an abdominal visceral artery was made and emergency surgery was therefore performed. A hematoma located in the transverse colonic mesentery was noted during the surgery. The hematoma was removed with the hemorrhagic colonic mesentery. A few days later, the patient was diagnosed as having hemorrhage from a ruptured dissecting aneurysm which was located near the branch of the middle colic artery. The patient’s postoperative course was uneventful. The pathological finding was segmental arterial Mediolysis (SAM), which is characterized by no inflammation, no arteriosclerosis, fusion of the tunica media and a medial island.
