IS Case 135: Renal Vein Varix
Imaging Sciences URMC 2008
Publication Date: 2009-05-21
Frequent incidental finding, renal varices can be idiopathic and found incidentally or associated with either renal vein thrombosis, obstruction or congenital anomalies of inferior vena cava, as well as azygous or portal hypertension [1,2]. Idiopathic renal varices demonstrate left predominance, with incidence of 6-10% in renal donors on phlebography [1,3]. Etiology of left predominance in idiopathic cases has been postulated to be stretching of this renal vein over aorta and compression between superior mesenteric artery (SMA) and aorta, the nutcracker phenomenon [1,4]. In addition, extensive collaterals from other organs and weakness of the wall of the vein may be contributing factors . Furthermore, absence of gonadal vein valves and abnormal collaterals between renal and gonadal veins have been suggested as contributing factors . In 31% of renal vein varix there is associated saphenous vein varicosity.
The extrarenal varices are more common than intrarenal . The latter may have calcifications and can simulate renal masses, especially if thrombosed [5,6]. The differential of renal varix includes renal or urothelial neoplasm, hemangioma, blood clots, pyelo-ureteritis cystica, leukoplakia, tuberculosis, and radiolucent calculi [4,5]. Failure to recognize characteristic appearance may lead to unnecessary nephrectomy .
Although the excretory urogram may demonstrate external compression of renal pelvis or proximal ureter by the varix, phlebography with or without epinephrine is a historic diagnostic modality of choice [1,6]. However, contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) noninvasively detect renal varices . The CT demonstrate attenuation matching and continuous with that of renal vein on pre and post-contrast images . The MRI demonstrates signal voids on axial spin-echo and T2-weighted images and high-signal on modified gradient echo and phase contrast with gadolinium imaging similar to that in other veins . The sagittal plane is especially useful for evaluation of nutcracker syndrome. In these patients MRA demonstrates acute take off angle of SMA from aorta . It could be used to diagnose this condition noninvasively, rather than demonstrating pressure gradient between the renal vein and IVC during venography . In addition, Technetium-99m red blood cells have been used to demonstrate pooling in a case of renal varix caused hematuria .
Pain with renal varices is extremely rare. They are typically asymptomatic and only infrequently associated with hematuria [5,8]. Whether renal varices actually cause hematuria is controversial . Nevertheless, surgical ligation or embolization are frequently used in patients with hematuria and/or pain and no other explanation . The transposition of the left renal vein to more caudal location has been successfully used in the nutcracker syndrome . Other complications include partial or complete obstruction and renal stone formation .
Renal vein varices are frequent incidental finding on CT or MRI. Intrarenal varices may mimic renal masses especially on non-contrast CT scans. The continuity with renal vein and similar appearance on all imaging modalities are important differentiating factors. The complications are rare and include hematuria, obstruction and stone formation. Surgical ligation or embolization may be used to treat varices associated with pain or hematuria.
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