Evaluation of a single-injection method for estimating glomerular filtration rate in dogs with reduced renal function

Two methods for evaluating glomerular filtration rate (GFR), after single i.v. administration of inulin, were assessed in dogs after partial nephrectomy. The first method, determination of plasma clearance of inulin (PCIn), was taken as the quotient of the administered dose of inulin (1,000 mg) divided by the area under the plasma inulin concentration vs time curve. The second estimate of renal function was obtained from the plasma concentration of inulin 75 minutes after i.v. administration of 1,000 mg: C(75). The values for PCIn and C(75) were related (R2 = 0.955, P < 0.0001 and R2 = 0.867, P < 0.0001, respectively) to a previously validated method for measurement of GFR in dogs, urinary clearance of exogenous creatinine (CCr). Results of this study support use of PCIn and C(75) values to estimate GFR in dogs with reduced renal function. In particular, PCIn and C(75) were closely related to CCr in partially nephrectomized dogs with plasma creatinine concentration within the reference range for clinically normal dogs.