Comparison of plasma disappearance and standard clearance techniques for measuring glomerular filtration rate in children with and without vesico-ureteric reflux.

The plasma disappearance rate, or slope clearance, after a single intravenous injection of 51Cr-EDTA was compared with simultaneously determined standard (UV/P) clearances of inulin, creatinine and 51Cr-EDTA in 4 healthy adults and 18 children with renal disease but no reflux. Slope clearance correlated well with standard inulin (r=0.99) and 51Cr-EDTA (r=0.97) clearances and was more accurate than creatinine clearance. Slope clearance x0.82 estimated standard 51Cr-EDTA clearance with +/- 12% accuracy in these subjects. In 18 children with vesico-ureteric reflux the correlations of the standard clearance methods with slope clearance were significantly reduced. Slope clearance may be measured with only two plasma samples and is recommended as the method of choice for determining glomerular filtration rate in children with gross reflux or impaired ability to empty their bladders.