New method for the determination of the maximum tubular transport (Tm PAH) of p-amino hippuric acid without urine analysis in children with renal transplants

For clearance studies in children with renal grafts methods without indwelling catheters in the urinary bladder are necessary. The determination of the glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) takes place by means of single injection of radioactively labelled clearance substances. The maximum tubular secretory function may be established by means of the Tm PAH. Up to now for this purpose the quantitative determination of PAH in the urine was necessary. By means of a basically other method by determination of 125I-hippuran clearance under infusion of PAH the Tm PAH may be indirectly calculated without investigation of the urine. In 9 children with renal diseases the parallel determination was performed with classical methods as well as with the new method, in order to prove the good correspondence of the two methods. The Tm PAH in 7 children with renal grafts was at first relatively decreased, after several years relatively increased compared to ERPF. (author)