[Bilateral Hydronephrosis and Erythrocytosis]

A 36-year-old woman who developed extreme erythrocytosis following partial correction of severe bilateral hydronephrosis by bilateral ureterolithotomy is presented. Hydronephrosis appears to stimulate renal synthesis and release of erythropoietin. The mechanism could involve increase in medullary hypoxia by increased pressure of the renal pelvis on the medullary vasculature. This might be especially marked when the renal blood supply is compromised by concomitant atherosclerosis, as in this case.