Renal biomarkers in domestic species

Current conventional tests of kidney damage and function in blood (serum creatinine and urea nitrogen) and urine (urine protein creatinine ratio and urine specific gravity) are widely used for diagnosis and monitoring of kidney disease. However, they all have important limitations, and additional markers of glomerular filtration rate and glomerular and tubular damage are desirable, particularly for earlier detection of renal disease when therapy is most effective. Additionally, urinary markers of kidney damage and function may help localize damage to the affected portion of the kidney. In general, the presence of high- and intermediate-molecular weight proteins in the urine are indicative of glomerular damage, while low-molecular weight proteins and enzymes in the urine suggest tubular damage due to decreased reabsorption of proteins, direct tubular damage, or both. This review aims to discuss many of these new blood and urinary biomarkers in domestic veterinary species, focusing primarily on dogs and cats, how they may be used for diagnosis of renal disease, and their limitations. Additionally, a brief discussion of serum creatinine is presented, highlighting its limitations and important considerations for its improved interpretation in domestic species based on past literature and recent studies.