The most common cause is thromboembolism. Emboli may originate in the heart (due to atrial fibrillation, after MI, or from vegetations due to bacterial endocarditis) or the aorta (as atheroemboli); less often, fat or tumor emboli are the cause. Thrombosis may occur in a renal artery spontaneously or after trauma, surgery, angiography, or angioplasty. Other causes of acute occlusion include dissection or rupture of a renal artery aneurysm.