A 9-year-old spayed female domestic shorthair cat was referred for erythrocytosis. Even after the correction of dehydration, blood analyses showed that there had been no improvement. An abdominal ultrasonography and computed tomography identified the presence of a mass on the left kidney. Measurement of serum erythropoietin (EPO) showed higher concentration than the reference interval. These findings suggested a direct association of the erythrocytosis with excessive EPO production. The cat underwent nephrectomy of the affected (left) kidney. Subsequent histopathology was consistent with a diagnosis of renal adenocarcinoma. Following the nephrectomy, serum EPO concentrations decreased gradually, and the erythrocytosis resolved 15 days postoperatively. This case describes the diagnosis and treatment of secondary inappropriate erythrocytosis in a cat with renal adenocarcinoma.

Key words: Erythropoietin, FELINE, Renal tumor