THE INTERRELATIONSHIPS AMONG FILTRATION SURFACE-AREA, BLOOD-PRESSURE, AND CHRONIC RENAL-DISEASE

A primary role for the kidney in hypertension has long been recognized, but the pathogenetic interactions among renal hemodynamics, hormonal and hereditary factors, and dietary sodium intake remain ill defined. Reduction in the filtration surface area, whether acquired in the course of intrinsic renal disease or after surgical renal ablation, leads to systemic hypertension as well as to progressive renal insufficiency, sequellae made even more severe by dietary sodium excess. Moreover, hypertension and progressive renal disease occur in some individuals born with a solitary kidney, and occur almost invariably with more severe degrees of dysgenesis. Hypertension is also commonly observed in certain inbred rat strains in which the filtration surface area is congenitally deficient. Based on these and other lines of evidence reviewed herein, we postulate that a renal abnormality that contributes to essential hypertension in the general population is a reduced number of glomeruli and tubules, the consequences of which are limitations in the ability to excrete sodium and thus salt-sensitive hypertension. Furthermore, congenitally decreased filtration surface area may explain why only some, but not all, patients exposed to potentially injurious renal stimuli eventually manifest chronic nephropathy, and may also account for the susceptibility of subsets of type I and type II diabetics to develop overt glomerulopathy. Clinically, tests of renal reserve capacity may serve as a useful guide to identification of those patients at risk for the development of hypertension and progressive renal disease.