Urinary Markers in Healthy Young and Aged Dogs and Dogs with Chronic Kidney Disease

Background: Blood urea nitrogen and serum creatinine concentrations only detect a decrease of >75% of renal functional mass. Therefore, there is a need for markers that allow early detection and localization of renal damage.
Hypothesis: Urinary albumin (uALB), C-reactive protein (uCRP), retinol binding protein (uRBP), and N -acetyl-β- d -glucosaminidase (uNAG) concentrations are increased in dogs with chronic kidney disease (CKD) compared with healthy controls and in healthy older dogs compared with young dogs.
Animals: Ten dogs with CKD, 10 healthy young dogs (age 1–3 years), and 10 healthy older dogs (age > 7 years) without clinically relevant abnormalities on physical examination, hematology, biochemistry, and urinalysis.
Methods: Urinary markers were determined using an ELISA (uALB, uCRP, and uRBP) or a colorimetric test (uNAG). Results were related to urinary creatinine (c). The fixed effects model or the Wilcoxon rank sum test were used to compare the different groups of dogs.
Results: uALB/c, uRBP/c, and uNAG/c were significantly higher in CKD dogs than in healthy dogs. No significant difference was found for uCRP, which was not detectable in the healthy dogs and only in 3 of the CKD dogs. Between the healthy young and older dogs, no significant difference was detected for any of the markers.
Conclusion: The urinary markers uALB/c, uRBP/c, and uNAG/c were significantly increased in dogs with CKD compared with healthy controls. Additional studies are needed to evaluate the ability of these markers to detect renal disease before the onset of azotemia.