Abstract
BACKGROUND: Combined measurement of functional, glomerular, and tubular markers in aging dogs is essential to detect early renal disease. OBJECTIVES: Prospective longitudinal study to describe renal function and assess which biomarkers are associated with the development of early renal disease or death. ANIMALS: One hundred and twenty-two apparently healthy senior and geriatric dogs. METHODS: Prospective longitudinal study. Renal function was evaluated at baseline (T0) and every 6-12 months over 2 years, using systolic blood pressure measurements (SBP) and validated serum (creatinine, symmetric dimethylarginine, cystatin C [sCysC]), and urinary (specific gravity [USG], protein:creatinine [UPC], albumin:creatinine, retinol-binding protein:creatinine [uRBPcr]) biomarkers. Glomerular filtration rate (GFR) was measured in a subgroup. Survival models were used to assess the predictive value of measured biomarkers at baseline for the onset of azotemic chronic kidney disease (CKD) or death, respectively. RESULTS: A total of 122 dogs were included; follow-up was available in 106 (T12) and 92 (T24); and GFR was estimated in 18 (T0), 11 (T12), and 10 (T24) dogs. Throughout the study, 15/122 (12%) dogs showed evidence of non-azotemic CKD, and in 11/106 (10%) dogs, azotemic CKD developed. Proteinuria was not associated with azotemic CKD, in contrast to muscle condition score, functional markers, and uRBPcr. Death was weakly associated with USG, UPC, and sCysC. CONCLUSIONS AND CLINICAL IMPORTANCE: Over a 2-year period, 20% (26/122) of older dogs developed CKD, mostly persistent renal proteinuria (15/122). Muscle wasting and functional markers combined with uRBPcr had the best predictive value for the onset of azotemic CKD in these older, previously apparently healthy dogs.