Blood pressure and proteinuria in older cats and cats with chronic kidney disease

Background and Aim: Systemic hypertension and proteinuria are key prognostic indicators in cats with chronic kidney disease (CKD). However, their interrelationship in older cats and those with CKD remains unclear. This study aimed to investigate the association between systolic blood pressure (SBP) and proteinuria in older cats and cats with CKD and evaluate the correlation of these parameters with hematological and biochemical markers. Materials and Methods: A cross-sectional observational study was conducted on 51 cats divided into three groups: 19 young adult cats (1-6 years, G1), 19 older cats (>10 years, G2), and 13 cats with CKD (creatinine >1.6 mg/dL, G3). Cats underwent clinical evaluations, blood pressure measurements using the oscillometric method, electrocardiography, and hematological, serum, and urine biochemical analyses. Statistical analyses included bootstrapped t-tests and Spearman's correlation, with significance set at p < 0.05. Results: SBP values did not significantly differ among groups, but absolute SBP values were higher in older cats (G2), suggesting a potential age-related trend. No significant correlations were found between SBP and proteinuria, creatinine, urea, or urine density in G2 and G3. However, kidney injury biomarkers (urinary protein-to-creatinine ratio, creatinine, and urea) were strongly correlated with weight, body score, and total plasma protein in CKD cats (G3), indicating disease progression. Furthermore, G3 exhibited significant reductions in hematocrit, hemoglobin, and red blood cell counts, which were associated with kidney dysfunction. Conclusion: This study did not find a direct correlation between SBP and proteinuria in older cats or cats with CKD. However, the higher SBP values in older cats highlight the importance of monitoring hypertension in aging felines. In addition, proteinuria was significantly associated with declining body condition and biochemical markers of kidney dysfunction, reinforcing its value as a prognostic indicator in CKD. Further studies are needed to explore the role of proteinuria and hypertension in advanced CKD stages.