Anemia in canine chronic kidney disease is multifactorial and associated with decreased erythroid precursor cells, gastrointestinal bleeding, and systemic inflammation

OBJECTIVE Compare erythropoiesis-related factors between different stages of canine chronic kidney disease (CKD). ANIMALS 8 healthy adult dogs (controls), and 24 dogs with CKD, equally divided into 3 groups based on International Renal Interest Society-CKD Guidelines (stage 2, 3, and 4) were recruited between December 2012 and December 2014. METHODS The following were assessed in all dogs and then compared between groups: bone marrow cytology, CBC, reticulo-cyte count, urinalysis, serum biochemistry, blood pressure, occult gastrointestinal bleeding, and serum concentra-tions of parathyroid hormone (PTH), erythropoietin, interleukin-1β, interleukin-3, tumor necrosis factor-α (TNFα), and interferon-γ. RESULTS Erythropoiesis inducing and suppressing factors and the results of the bone marrow cytology of dogs in stage 2 CKD did not differ from the control group. The presence of reticulocytosis in CKD stage 2 suggests that blood loss or erythrocyte destruction might be contributing to developing anemia. Anemia in dogs with progressive CKD was associated with increasing PTH and TNFα and with elevation of the ratio of myeloid to erythroid precursor cells caused by hypoplasia of the erythroid series. The latter was represented mainly by a decrease in the population of polychromatophilic rubricytes and metarubricytes. CLINICAL RELEVANCE Increased PTH and TNFα seem to contribute to the reduced percentage of polychromatophilic rubricytes and ery-throid population, thereby aggravating the anemia of dogs with advanced CKD. Gastrointestinal blood loss contrib-utes to anemia in all canine CKD stages.