Late Development of a Large Arteriovenous Fistula with Aneurysm in an In Situ Vein Bypass Graft

We report a case of saphenous vein bypass aneurysm and arteriovenous fistula in a 65-year-old man, 20 years after an in situ vein bypass for occlusive disease. He was found to have patent venous branches which kept the bypass open despite distal anastomotic occlusion. The saphenous vein was successfully excised without distal revascularization due to sufficient native arterial flow. This is the first reported case of aneurysmal degeneration of an in situ vein conduit with occluded distal anastomosis and patent venous side branches. Ultrasound surveillance is warranted for all bypass procedures, and early endovascular or open revisions can prevent late complications.