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Renal vein entrapment syndrome: frequency and diagnosis. A lesson in conservatism.

Two boys investigated for gross hematuria and left loin pain were found on ultrasound (US) to have left renal vein (LRV) entrapment associated with isomorphic urinary red blood cells, but normal renal venograms. Over the next 18 months ten children with gross hematuria were investigated and two more boys were discovered with the LRV entrapment syndrome, i.e., isomorphic red cells and a diagnostic US. Venography has a low yield in detecting renal venous compression, and since urinary red cell morphology may localize the origin of renal bleeding, we strongly recommend simple procedures, i.e., phase microscopy and renal US to evaluate all cases of hematuria before employing invasive or radiation dependent investigations. Since there is a range of LRV compression and associated dilatation in asymptomatic patients, strict criteria must be applied to diagnose renal vein entrapment.