Polycythemia in a Patient With Atonic Bladder and Hydronephrosis.

Kidneys influence the production of red blood cells by secreting most of the erythropoietin (EPO) in adults. Consequently, renal diseases often impact erythropoiesis and hemoglobin levels. Chronic kidney diseases lead to anemia due to EPO deficiency. However, erythrocytosis can occur in patients with cystic diseases of the kidney and renal artery stenosis due to upregulation of hypoxia-inducible factors (HIFs) and increased EPO production. Here, we present a patient with secondary polycythemia who was found to have atonic bladder and hydronephrosis. Resolution of hydronephrosis led to the reversal of erythrocytosis, highlighting the intricate regulation of red cell production.