The relationship between renal cortical volume and predisposition to hypertension

It has been proposed that a reduction in the number of nephrons is a renal abnormality that plays an important role in the pathogenesis of essential hypertension. The objective of this study was to determine whether renal cortical volume, used as a measure of the number of nephrons, is lower in normotensive subjects with a familial predisposition to develop essential hypertension than in subjects who lack this predisposition. For this purpose, we measured renal cortical volume using electron beam computed tomography in 26 white offspring of two hypertensive parents (OHT; 14 women, 12 men) and 27 white offspring of two normotensive parents (ONT; 13 women, 14 men) who were stabilized on a high sodium diet for 3 days (200 mmol/day). In women, mean age was significantly greater in OHT than ONT (46.1 +/- 4.9 [standard deviation] v 41.8 +/- 5.1 years, respectively, P = .04). In men, means for age and weight were greater in OHT than ONT (age: 47.1 +/- 7.7 v 37.9 +/- 8.1 years, P < .01; weight: 90.2 +/- 10.7 v 81.1 +/- 9.4 kg, P = .03.) In women, mean total cortical volume did not differ significantly between OHT and ONT (156 +/- 33.3 v 166 +/- 30.9 cc, P = .80). After adjustment for interindividual differences in age, mean total cortical volume remained not significantly different in OHT than ONT (160 +/- 29.0 v 162 +/- 32.4 cc, P = .83), In men, mean total cortical volume was significantly greater in OHT than ONT (210 +/- 33.6 v 180 +/- 20.0 cc, P < .01). After adjustment for interindividual differences in age, mean total cortical volume remained significantly greater in OHT than ONT (207 +/- 33.2 v 182 +/- 19.8 cc, P = .02). After adjustment for interindividual differences in body weight, mean total cortical volume did not differ significantly between OHT and ONT (201 +/- 21.7 v 187 +/- 20.1 cc, P = .09). The results of this study do not support the hypothesis that a decrease in renal cortical volume, as a result of a decrease in number of nephrons, is a characteristic of white women or men with a familial predisposition to develop essential hypertension.