An 18-cm-large renal arteriovenous fistula treated by nephrectomy.

Idiopathic renal arteriovenous fistulas are extremely rare. They are believed to occur as the result of congenital renal artery aneurysm that erodes into an adjacent vein. We report a case of a 48-year-old man in whom we discovered fortuitously a painless mass of the right flank. Computed tomography revealed a huge renal artery aneurysm with giant arteriovenous fistula in the absence of any clinical stigmata. Given the size of the fistula and the partial destruction of the renal parenchyma, nephrectomy was successfully performed.