Correlation of Urine Protein/Creatinine Ratio and Twenty‐Four‐Hour Urinary Protein Excretion in Normal Cats and Cats with Surgically Induced Chronic Renal Failure

Urine protein/creatinine (UP/C) ratios and 24‐hour urinary protein excretion were compared in clinically normal cats and cats with surgically induced chronic renal failure (CRF). Mean 24‐hour urinary protein excretion in 30 clinically normal cats fed a 28% protein diet (dry weight basis) was 4.93 mg/kg/ 24‐hour (SD = 1.34) with a range of 2.99 to 8.88. Mean UP/C ratio in these cats was 0.134 (SD = 0.037) with a range of 0.073 to 0.239. Mean 24‐hour urinary protein excretion in CRF cats was 10.49 mg/kg/ 24‐hour (SD = 11.28) with a range of 2.16 to 62.93. Mean UP/C ratio in the CRF cats was 0.359 (SD = 0.374) with a range of 0.061 to 1.916. Linear regression showed high correlation (R²= 0.973, P < 0.001) between 24‐hour urinary protein excretion and UP/C ratio in clinically normal cats and cats with surgically induced chronic renal failure. The regression equation for 24‐hour urinary protein excretion versus UP/C ratio was: 24‐hour urinary protein excretion = 29.39 (UP/C) + 0.18. Results of this study indicate that UP/C ratios are a valid estimate of 24‐hour urinary protein excretion in clinically normal and CRF cats. Dietary protein intake significantly affected UP/C ratios in clinically normal cats and cats with surgically induced CRF. Therefore, the influence of dietary protein should be considered when interpreting UP/C ratios. (Journal of Veterinary Internal Medicine 1992; 6:36–40)