Endovascular Aneurysm Repair for a Patient with Horseshoe Kidney and the Importance of Watershed Sign and Volumetry by Preoperative Contrast-Enhanced Computed Tomography.

We report a case of endovascular aneurysm repair (EVAR) in a patient with horseshoe kidney (HSK) in whom preoperative contrast-enhanced (CE) computed tomography (CT) showed watershed sign. This sign enabled prediction of postoperative renal function by accurate renal volumetry. A 75-year-old man with HSK and a 59-mm abdominal aortic aneurysm was referred for treatment. Preoperative CECT showed watershed lines at the margin of the isthmus, which was perfused by the accessory renal arteries. Using this sign, we calculated the accurate volume of the isthmus, which was 24.5% of the total parenchyma. EVAR was safely performed without renal dysfunction.