Simultaneous Determination of Renal Blood Flow and Glomerular Filtration Rate without Ureteric Catheterization

Abstract

Clearance determination by combined measurement of renal blood flow, using a dye-dilution method, and the extraction of a suitable test substance can have important advantages over the conventional separate clearance determinations based on the principle of urine collection. Ureteric catheterization is not required. After constant blood-concentration has been obtained the determinations are made in a few minutes. the glomerular filtration rate can be determined by the use of ⁵¹Cr-EDTA; the analytical procedure is much simpler than for inulin. Clearance determined by the proposed method was in good agreement with clearance determined in the conventional way, the ratio for the two methods being 1.03; r = 0.89. Other renal clearances can also be determined by the combined technique proposed. Preliminary studies have therefore been carried out using ¹²⁵I-hippuran as a substitute for PAH. Finally the accuracy of the dye-dilution method has been further checked by comparing the determination of renal blood flow according to this method with that performed using ¹²⁵I-hippuran according to Fick's principle. There was good agreement between the results of the two methods, the ratio being 1.01; r = 0.88.