Spontaneous aorto-left renal vein fistula: the "abdominal pain, hematuria, silent left kidney" syndrome. Spontaneous aorto-left renal vein fistula (ALRVF) is a rare occurrence; with this case, only 16 have been reported to date. Common features in patients with ALRVF include abdominal pain (81%), hematuria (100%), impaired renal function (85%), and nonvisualization of the left kidney (100%). Less common but also present in the majority of cases are a left sided bruit (73%), pulsatile abdominal mass (63%), and proteinuria (50%). Also important, 94% have a retroaortic left renal vein, unlike the six cases of traumatic ALRVF that have been reported. This magnifies the diagnostic value of contrast abdominal computed tomographic scanning, which demonstrates not only the anomalous location of the left renal vein but also the abdominal aortic aneurysm and poor enhancement of the left kidney. These findings rule out the possibility of the "nutcracker syndrome" (left renal vein compression between aorta and superior mesenteric artery). Although confirming the presence of a fistula by early caval opacification, aortography does not always distinguish ALRVF from the more common aortocaval fistula. This can be accomplished by Duplex scanning with deep probes and even preferably color coding of velocity signals. With such precise preoperative localization, surgical repair is relatively easy and safe. 