Evaluation of plasma clearance of inulin in clinically normal and partially nephrectomized cats

To evaluate accuracy of measuring plasma clearance of inulin as an alternative renal function test for estimation of glomerular filtration rate (GFR) in cats.

10 cats, first studied with intact kidneys and subsequently studied following partial nephrectomy.

Clearance studies were performed in 10 clinically normal cats; those same cats then underwent partial nephrectomy, and clearance studies were performed again. Plasma concentration of inulin was determined after administration at 50 mg/kg of body weight to cats while renally intact and 45 mg/kg after the partial nephrectomy. Plasma clearance of inulin (PCin) was determined by dividing the dose by the area under the plasma inulin concentration versus time curve. Results for PCin were compared with values obtained simultaneously for urinary clearance of exogenously administered creatinine (Ccr), a widely accepted method for measurement of GFR in cats with intact kidneys and cats with reduced renal mass.

Results of PCin were strongly correlated (r2 = 0.912, P < 0.001) with Ccr. Repeatability of determination of PCin was similar to that of Ccr. Sensitivity and specificity of PCin were superior and equivalent to that of Ccr, respectively.

Determination of PCin provides a reliable estimate of GFR in cats and is a promising alternative to determining Ccr in cats.