Erythrogram patterns in chronic kidney disease of dogs

Anaemia is considered a common finding in dogs with chronic kid- ney disease (CKD), typically as normochromic, normocytic, and non-regenerative. Although anaemia could be occurring at any CKD IRIS stage, its severity has been related with the loss of kidney function. The aim of the present study was to retrospectively evaluate quantita- tive and morphological abnormalities of the erythrogram in dogs at different CKD IRIS stages. The study included erythrogram of azotaemic dogs with docu- mented history, laboratory, and ultrasonographic findings of CKD. Exclusion criteria were represented by 1) rechecks of the same patient; 2) dogs with history, laboratory and/or ultrasonographic findings, consistent with acute kidney injury (AKI); 3) missing report of the blood smear evaluation; 4) use of alpha-darbepoetin or red blood cell transfusion prior to presentation. Median values of the CBC parameters were compared among the CKD groups (IRIS stag- ing) through Kruskal Wallis test and Dunn's multiple comparisons test. Chi squared test was used to compare the frequency, and the degree of anaemia (mild, moderate, severe), regeneration rate (num- ber of reticulocytes), and morphological abnormalities among differ- ent CKD groups. A total of 482 dogs over 3,648 initially screened, were included in the study. Anaemia was present in 302/482 (63%) dogs, in the majority of which it was normochromic, normocytic, and non-regenerative (295/302; 98%). The number of reticulocytes was <60,000 /μL in the majority of dogs (248/295; 84%), with a strong correlation between poor regeneration and progression of CKD (p=0.0001; Phi=1.03). The frequency of anaemia significantly differed (p=0.0001) among the IRIS stages: 108/231 (47%) in IRIS 2, 77/109 (71%) in IRIS 3, and 117/142 (82%) in IRIS 4. Dogs at IRIS stage 3 and 4 were more likely to have moderate to severe anaemia, compared to dogs at IRIS stage 2 (p=0.0001). Anisocytosis (291/482; 60%) was the most frequent morphological abnormality of the erythrogram in the study popula- tion, although no association with the progression of CKD was noticed. Anaemia was frequently found in CKD dogs, mostly associated with poor regeneration rate. Although anaemia may be present at any IRIS stage, its frequency and its degree of severity were associated with the loss of kidney function. Similarly to human medicine, advanced canine CKD IRIS stages are more frequently characterized by none to poor regeneration rate, compared to early stages. These findings may suggest a more severe condition of impaired bone marrow activity and erythropoietin deficiency.