Many aging cats have renal disease leading to renal insufficiency and failure. The pattern of progression varies, with some cats remaining mildly azotemic for years after initial diagnosis. In humans with naturally occurring renal disease, proteinuria is an independent risk factor for progressive loss of renal function. Leakage of protein across the glomerulus can lead to further kidney damage. This may also be important in cats with renal disease. Two studies of naturally occurring chronic renal failure in cats have shown that proteinuria can be used to predict long-term survival. In the first study of 117 cats, a urine protein to creatinine (UPC) ratio above 0.43 predicted survival. The second study of 193 cats found an inverse correlation between initial UPC ratio and survival time in the placebo group. It is not clear whether treatment of cats with antiproteinuric drugs will improve survival, but studies are currently underway.

COMMENTARY: Because renal disease is such an important factor in the health of aging cats, anything that can be done to slow the progression of disease is important. The earlier the disease can be identified the better. Diagnostic tests are now available that can detect microalbuminuria, allowing earlier recognition of disease.

Importance of proteinuria in cats with chronic renal failure. Elliott J. ACVIM PROC, 2004, pp 708-709.