Diagnostic utility of different models used to assess the acid-base balance in cats with chronic kidney disease.

Metabolic acidosis is diagnosed based on the concentration of bicarbonate ions and partial pressure of carbon dioxide in arterial blood, although acid-base balance (ABB) disorders may also be diagnosed based on the serum ion concentrations in order to determine the values of strong ion difference (SID), anion gap (AG), corrected anion gap (AGcorr) and chloride/sodium ratio (Cl-/Na+). The aim of this study was to assess and compare the classic model, the value of the AG, AGcorr, and Cl-/Na+ in the diagnosis of ABB disorders in cats with chronic kidney disease (CKD). The study group consisted of 80 cats with CKD, divided into four groups based on the guidelines of the International Renal Interest Society (IRIS). The control group (C) included 20 healthy cats. Metabolic acidosis - diagnosed based on the classic model (Hendersson-Hasselbalch equation) - was found in IRIS group IV. AG, AGcorr, SID calculated for IRIS groups II, III and IV were lower than in group C, while the value of AGdiff and Cl-/Na+ in those groups was higher than in group C. We can conclude that ABB analysis using the classic model enabled the detection of ABB disorders in cats in stage IV CKD. However, the analysis of the AG, AGcorr and Cl-/Na+ values enabled the diagnosis of acid-base balance disorders in cats with IRIS stage II, III and IV CKD.