A 63-year-old woman presented to our emergency department with an acute onset of severe right flank pain and tachycardia. Abdominal computed tomography (CT) revealed massive retroperitoneal extravasation (thin arrow, Fig. A) arising from right renal angiomyolipoma (AML) containing fat density (thick arrow, Fig. A) within a non-calcified soft tissue mass. Angiography revealed an aneurysm (arrow, Fig. B) arising from renal artery, and subsequent embolization was performed successfully. The patient recovered uneventfully. Follow-up CT scan obtained seven months after embolization shows well-defined renal contour and lipomatous components of the tumor (arrow).