Assessment of renal functional reserve by dynamic renal function testing.
Renal clearances of suitable clearance markers such as inulin and p-aminohippurate, determined before and after protein load, have been used for a long time to determine glomerular filtration rate (GFR), renal blood-flow, renal functional reserve as well as renal vascular resistance. Despite this long history, inconsistent results were achieved in determining renal functional reserve after protein ingestion or aminoacids infusion. Most authors found acute 'blunted increases' in GFR after dietary stresses, whereas others found acute decreases. In hypertensive patients showing hyperfiltration, a contradictory situation was observed; the traditionally observed 'blunted increase' in GFR and increase in the intraglomerular pressure were neither accompanied by a change in albumin excretion nor by an expected dynamic GFR response after administration of angiotensin converting enzyme (ACE)-inhibitors. We are of the opinion that the traditional clinical methods for assessing acutely provoked changes in renal function have been inappropriate and that an approach based on the two-compartment model of pharmacokinetics is more adequate for studying dynamic clearance changes within clinically feasible time horizons. Such test evaluations performed in patients within a washout period, and after long-term treatment with various drugs enable one to assess the efficacy of the therapeutic regimens especially in patients showing apparently normal or increased baseline clearances in hyper filtering kidneys.
Zitta
Sabine
S
Department of Medicine, Division of Nephrology, University of Graz, Austria.
Holzer
Herwig
H
Estelberger
Willibald
W