Purpose. To describe the treatment of renal artery thrombosis with ultrasound-accelerated thrombolysis and discuss the management of prolonged renal ischemia. Case. A 76-year-old patient with a single functional kidney, mild chronic renal impairment, and a recent history of endovascular repair of a thoracoabdominal aneurysm with an aortic branch graft presented with acute flank pain, anuria, and renal failure. The side branch from the aortic stent graft to his single, right, functional kidney appeared to be completely thrombosed. Symptoms had started after cessation of oral anticoagulants because of a planned mastectomy for breast cancer. After identification of the occlusion, ultrasound-accelerated thrombolysis was started 19 hours after the onset of anuria. Angiography, 4 hours after beginning of therapy, already showed partial dissolution of the thrombus and angiographic control after 18 hours showed complete patency of the renal artery side branch. Despite a long period of ischemia, renal function was completely recovered. Conclusion. In patients with acute renal ischemia due to thrombosis of the renal artery, complete recovery of function can be achieved with ultrasound-accelerated thrombolysis, even after prolonged periods of ischemia.