Kidney diseases constitute a significant clinical problem in dogs and cats due to the extended lifespan of animals and, most often, the co-occurrence of other chronic diseases. Acute kidney injury (AKI) is a clinical condition with a sudden deterioration of their filtration function developing for various reasons and characterized by high mortality. Chronic kidney disease (CKD), in turn, is a progressive, irreversible loss of nephron function as a result of pre-existing inflammation, tubulointerstitial kidney diseases, stones or systemic diseases damaging the kidneys such as hypertension, diabetes, infectious diseases (including leptospirosis, babesiosis, leishmaniasis).