Hemoperitoneum due to aneurysm rupture related to systemic lupus erythematosus: a case report.

Although systemic lupus erythematosus (SLE) is often associated with aneurysm formation, hemoperitoneum due to SLE-related abdominal visceral aneurysm is rare. A 53-year-old man with a 21-year history of SLE presented to our hospital with abdominal pain. Contrast-enhanced computed tomography revealed extravasation around a branch artery of the inferior mesenteric artery (IMA), suggesting hemorrhage from the same region. Emergency laparotomy was performed due to patient's declining condition. A large hematoma in the mesentery of the splenic flexure of the descending colon was observed, and resection of the descending colon and hematoma was performed. Pathological examination revealed aneurysmal dilation of an IMA branch within the hematoma. Affected blood vessels exhibited extreme thinning due to fibrinoid necrosis, possibly caused by SLE. The patient was discharged 28 days after the initial surgery without complications. Aneurysm rupture should be considered in the differential diagnosis of acute abdomen in patients with SLE.