Use of plasma clearance of inulin for estimating glomerular filtration rate in cats

Abstract

Objective: To evaluate utility of a method for estimating glomerular filtration rate after a single i.v. injection of inulin.

Animals: Cats that were renal intact (n = 3) or had renal mass reduced by partial nephrectomy (n = 6).

Procedure: Plasma clearance of inulin (PCln) was taken as the quotient of the administered dose of inulin (150 mg) divided by the area under the plasma inulin concentration versus time curve determined by 3 methods (PCln1-PCln3). Results for PCln were compared with simultaneously obtained values for urinary clearance of exogenous creatinine (CCr), an accepted method for the estimation of glomerular filtration rate (GFR) in cats.

Results: Values for PCln were closely related (R2 ranged from 0.951 to 0.972, P < 0.0001 in all instances) to CCr. However, PCln3 provided an estimate of GFR that consistently overestimated CCr.

Conclusion: Determination of PCln by use of PCln1 and PCln2 provided a reliable estimate of GFR in cats of this study.

Clinical relevance: Determination of PCln appears to provide a reliable estimate of GFR in cats with early-stage renal disease and no evidence of derangement of body fluid status. In particular, PCln2, which requires only 3 determinations of plasma inulin concentration, should be considered when an estimate of GFR is sought in a cat with suspected early-stage renal disease.