Glomerular filtration rate evaluation in the dog throughout the plasmatic clearance of iohexol: Simplified methods

GFR (glomerular filtration rate - GFR) shows the rate of glomerular filtration through renal glomeruli and, despite of the most used paramethers for the evaluation of renal disfunction (plasmatic creatinine, urea and urinary specific gravity), allows an early diagnosis of renal failure. Iohexol, a non-ionic low osmolarity contrast medium, has renal clearance only and can be used as a reliable GFR marker in humans and animals. The pourpose of the present study was to establish simplified methods of GFR determination in dogs through the plasmatic clearance of iohexol and to evaluate the accuracy of Cockroft-Gault equations GFR prediction. In the 35 dogs of our study the plasmatic concentration of iohexol was directly evaluated by using an HPLC method. A linear regression analysis among the reference 11-point method (5, 15', 30', 45" 60', 90" 180', 240', 300', 420'e 24 hours) and the four simplified five-sample models was performed. The best time for sampling in the 5-sample method was 5, 15, 60, 90 and 180 minutes. The linear regression analysis among the reference 11-point method and the equations for the prediction of GFR in the dog showed no significant correlation. GFR determination can be considered the only reliable method to assess renal function in dogs. Plasma clearance of iohexol can be estimated in dogs from 5 blood samples with a reasonable margin of error and used as a good routine method of GFR evaluation in early diagnosis of nephropaties