Abstract
Background:
Anemia is a common systemic complication of chronic kidney disease (CKD) in cats, arising mainly from insufficient endogenous erythropoietin synthesis and impaired iron utilization. These disturbances reduce oxygen delivery, worsen clinical status, and accelerate CKD progression. Although recombinant human erythropoietin (rHuEPO) is used in selected cases, detailed evaluations of its therapeutic performance in veterinary practice remain limited.

Aim:
This study investigated the hematologic and biochemical response to an erythropoietin-based treatment protocol in anemic cats diagnosed with CKD.

Methods:
The control group (Control I) consisted of healthy cats (n = 10). Following stabilization, cats were randomly allocated into two equal groups (n = 10 per group):Group I: Received standard CKD management, including a prescription renal diet, phosphate binders (lanthanum carbonate), and subcutaneous fluid therapy as required; Group II (rHuEPO-treated): Received the same standard therapy supplemented with recombinant human erythropoietin (rHuEPO; Eprex®, 1000 IE/0.5 ml, Janssen-Cilag, Switzerland) administered subcutaneously at a dose of 100 IU/kg, three times weekly for 28 days. Clinical evaluations and sample collections were carried out on days 0, 7, 14, 21, and 28 Blood and urine samples were collected at baseline and at subsequent checkpoints. The following parameters were assessed: hematocrit, hemoglobin, erythrocyte count, reticulocytes, serum iron markers (iron, ferritin, TIBC), creatinine, blood urea nitrogen (BUN), and urine protein-to-creatinine ratio (UPC). Temporal dynamics were analyzed to determine treatment effectiveness.

Results:
Clinically, CKD cats presented with dehydration, chronic wasting, and small irregular kidneys on palpation, with ultrasonography confirming bilateral cortical thinning. Hematologically, affected cats exhibited significant normocytic, normochromic, non-regenerative anemia (RBC 4.35±0.14×10¹²/L; HGB 84.5±1.27 g/L; p<0.01) and reduced thrombocytes. Biochemically, azotemia was evident (urea 11.18±0.22 mmol/L; creatinine 172.4±1.11 µmol/L; p<0.01). Despite elevated serum iron (16.78±0.07 µmol/L), ferritin (137.30±1.25 µg/L) and endogenous EPO (0.64±0.03 pmol/L) were significantly decreased. Urinalysis confirmed proteinuria (UPC 0.68±0.008) and cylindruria (2.74±0.48 casts/hpf). rHuEPO therapy (Group II) normalized erythrogram parameters, renal markers, and urinalysis by day 28, with efficacy significantly exceeding standard care (Group I).

Conclusion:
Subcutaneous rHuEPO effectively corrected anemia in feline CKD, producing early reticulocyte activation, sustained improvement of red cell indices, normalization of iron parameters, and stabilization of renal biomarkers.

Key words: Anemia; Cats; Chronic kidney disease; Erythropoietin; Hematology.