Summary
To evaluate renal function and obtain reference values for measurements of urinary excretion of various substances, quantitative urinalysis was performed in healthy, growing kittens from 4 to 30 weeks after birth. Endogenous creatinine clearance, 24-hour urine protein excretion, and urine protein-to-creatinine ratio were determined. Additionally, fractional excretion to creatinine clearance was calculated for calcium, inorganic phosphorus, sodium, potassium, and chloride. Mean ± SD endogenous creatinine clearance values (range, 3.80 ± 0.48 to 4.74 ± 0.61 ml/min/kg) were significantly (P < 0.0001) higher in kittens 9 to 19 weeks old, compared with younger (range, 1.39 ± 0.85 to 3.59 ± 0.86 ml/min/kg) and older kittens (range, 2.69 ± 0.40 to 3.46 ± 0.37 ml/min/kg). Mean values for all kittens for 24-hour urine protein excretion (range, 2.54 ± 1.81 mg/kg at 4 weeks to 11.39 ± 7.61 mg/kg at 14 weeks) and for urine protein-to-creatinine ratio (range, 0.14 ± 0.03 to 0.34 ± 0.18) varied from week to week of age. The urine protein-to-creatinine ratio in kittens > 9 weeks old correlated well (R2 = 0.861) with 24-hour urine protein excretion. Urinary fractional excretion of calcium, inorganic phosphorus, sodium, potassium, and chloride in kittens varied among age groups, being significantly (P < 0.01) different for potassium and calcium in young kittens (4 to 6 weeks) and older kittens (≥ 7 weeks).
