Intrarenal arteriovenous fistula causing a "pseudonutcracker effect"

We report a case in which an intrarenal arteriovenous fistula caused the nutcracker effect. Color Doppler sonography of the left renal artery showed a peak systolic velocity of 150 cm/second and renoaortic ratio of 2.1. The left renal vein was significantly dilated, and the adjacent renal artery was kinked. A stenosis in the left renal vein at the aorto-mesenteric bifurcation was demonstrated, with a maximum velocity of 201 cm/second. Renal Doppler evaluation showed an area of high-velocity, low-resistance arterial flow consistent with an arteriovenous fistula in the inferior half of the left kidney. Angiography confirmed the fistula. The fistula was successfully occluded by coil embolization. Follow-up sonography showed almost complete obliteration of the fistula, regression of the renal vein dilatation, and a reduction in renal venous and arterial flow velocities. Given the reversibility of the fistula's effects, we suggest the term "pseudonutcracker effect" to describe this case.