Retroperitoneal Hematoma: Rupture of Aneurysm in the Arc of Bühler Caused by Median Arcuate Ligament Syndrome.

We herein report a case with aneurysm rupture in the arc of Bühler (AOB) caused by median arcuate ligament syndrome (MALS). The patient experienced a sudden onset of upper abdominal pain. Contrast-enhanced abdominal computed tomography (CT) showed an iso- to hyper-enhancing area mainly ranging from the dorsal aspect of the pancreatic head to the retroperitoneum around the right kidney. Abdominal angiography revealed marked stenosis in the origin of the celiac artery caused by MALS and a 7-mm saccular aneurysm in the AOB. Thus, we diagnosed the pain as having been caused by aneurysm rupture in the AOB due to MALS. The patient's symptoms and anemia also improved to normal range without surgery. Careful follow-up, considering possible recurrence of aneurysm at other sites in the future, is essential.