A 30-year-old man was admitted to the Kitami Red Cross Hospital for the evaluation of erythrocytosis. Laboratory findings on admission was as follows: RBC, 697×104/mm3; hemoglobin, 22.0 g/dl; hematocrit, 67%, WBC, 6,700/mm3; platelet, 16.1×104/mm3; arterial oxygen saturation, 96.4%; and red blood cell mass, 46.4 ml/kg. Scintiscans of liver and spleen showed a slight degree of splenomegaly. A stenosis of left renal artery was documented by arteriography. The erythropoietin activity of peripheral blood, which was determined by the CFU-E colony assay method, was elevated. From these findings a diagnosis of secondary erythrocytosis was made. Blood samples were obtained by simultaneous catheterization of the renal veins and inferior vena cava for the assay of erythropoietin. The Erythropoietin activity of left renal vein was significantlly higher than those of right renal vein and of inferior vena cava at the level of L4. The association between polycythemia and renal artery stenosis was discussed.
