Influence of kidney function on urinary excretion of albumin and retinol-binding protein in dogs with naturally occurring renal disease.

OBJECTIVE: To evaluate excretion of urinary albumin (UAlb) and urinary retinol-binding protein (URBP) in dogs with naturally occurring renal disease. ANIMALS: 64 client-owned dogs. PROCEDURES: Dogs were assigned to groups according to plasma creatinine concentration, urinary protein-to-urinary creatinine ratio (UP:UC), and exogenous plasma creatinine clearance (P-Cl(Cr)) rates: group A (n = 8), nonazotemic (plasma creatinine < 125 μmol/L) and nonproteinuric (UP:UC < 0.2) with P-Cl(Cr) rate > 90 mL/min/m²; group B (26), nonazotemic and nonproteinuric with P-Cl(Cr) rate 50 to 89 mL/min/m²; group C (7), nonazotemic but proteinuric with P-Cl(Cr) rate 53 to 98 mL/min/m²; group D (8), azotemic and borderline proteinuric with P-Cl(Cr) rate 22 to 45 mL/min/m²); and group E (15), azotemic and proteinuric (P-Cl(Cr) not evaluated). The UAlb and URBP concentrations were measured via ELISA; UAlb-to-urinary creatinine (UAlb:UC) and URBP-to-urinary creatinine (URBP:UC) ratios were determined.
RESULTS: UAlb:UC and URBP:UC did not differ between groups A and B. Increased UAlb: UCs and URBP:UCs were paralleled by increased UP:UCs in groups C, D, and E relative to values from groups A and B, independent of azotemia. There were significant positive correlations of UP:UC with UAlb:UC and of UAlb:UC with URBP:UC (r = 0.82 and 0.46, respectively). However, UP:UC, UAlb:UC, and URBP:UC were not significantly correlated with P-ClCr rate. CONCLUSIONS AND CLINICAL RELEVANCE: UAlb and URBP concentrations were paralleled by urinary protein concentrations and may be useful in assessing renal management of plasma proteins. Determination of urinary protein, UAlb, or URBP concentration was not sufficiently sensitive to detect reduced P-Cl(Cr) in nonazotemic dogs.