Misdiagnosis of Anterior Superior Pancreaticoduodenal Artery Aneurysm Rupture Likely Due to Segmental Arterial Mediolysis: A Case Report

An aneurysm of the abdominal internal organs is relatively rare. Recently, segmental arterial mediolysis (SAM) and median arcuate ligament syndrome (MALS) were identified as specific causes for aneurysms of the pancreaticoduodenal artery arcade. Herein, we report a ruptured anterior superior pancreaticoduodenal artery (ASPDA) aneurysm due to SAM that was misdiagnosed as acute pancreatitis. The patient was a 59-year-old male with acute, severe, and sharp pain in the upper abdomen. He was clinically diagnosed with acute pancreatitis based on abdominal computed tomography (CT). However, a follow-up CT scan revealed an aneurysm of the ASPDA. We therefore diagnosed this case as retroperitoneal hemorrhage due to aneurysm rupture, and we performed an angiogram and transcatheter arterial embolization to prevent aneurysm re-rupture. Based on a subsequent review of all the findings for this patient, we retrospectively determined the cause of the ASPDA aneurysm to be SAM. Such case reports are rare, and further accumulation of similar cases is necessary in the near future to establish proper diagnostic criteria and appropriate treatment protocols