When renal arterial thrombosis occurs, the etiologic process plays an important role in the impact of ischemia on renal tissue. If the occlusion is caused by trauma, infarction rapidly occurs. However, when renal arterial thrombosis results from other processes, collateral vessels may develop and thus enables a prolonged ischemia without necrosis. The following is a case report of an acute renal failure caused by renal arterial thrombosis of a single functional kidney, which had a favorable outcome despite delayed treatment by percutaneous angioplasty. This report suggests that detection by ultrasonography of a venous renal flow could be of significant value to assess a collateral vascularization and thus should require an arteriography with angioplasty even after a delayed presentation.