A case report: spontaneous rupture of dissecting aneurysm of the middle colic artery.

Aneurysms of the superior mesenteric artery branches are rarely reported, even among them colic artery aneurysms are seldom. We report a case of 78-year-old male with ruptured dissecting aneurysm of middle colic artery. The patient complained abdominal pain and nausea during hospital stay for renal stone. The patient suddenly developed severe abdominal pain, leading to shock. He underwent emergency surgery under a preoperative diagnosis of intraperitoneal hemorrhage. At exploratory laparotomy, a large hematoma involving the mesentery root of the transverse colon was associated with a ruptured aneurysm measuring 15 x 10 mm in size, which was located to the mid-portion of middle colic artery. Right-hemicolectomy was carried out because of ischemic changes in the ascending colon. Histological examination demonstrated a ruptured dissecting aneurysm of the middle colic artery approximately 5 cm in length, associated with destruction of the tunica interna and media. The aneurysm was thought to result from idiopathic segmental arterial mediolysis, because no definitive evidence of atherosclerosis or arteritis was observed.