Renal Hemodynamics in Patients With Sustained Essential Hypertension and in Patients With Unilateral Stenosis of the Renal Artery

Systemic and renal hemodynamics including split renal function tests were studied in 41 patients with renovascular hypertension (RVH) related to unilateral stenosis of main renal artery in comparison to 36 subjects with essential hypertension (EH). The two populations were matched for age, sex, body surface area, and systemic arterial pressure. Cardiac output and total peripheral resistances were similar in both groups, with total peripheral resistances increased in comparison to normal values (P < .001). Patients with EH had a decreased blood volume (P < .01) with a normal cardiopulmonary blood volume. Patients with RVH had a normal blood volume with an increase in cardiopulmonary blood volume (P < .02). The para-amino hippurate clearance (CPAH) was decreased in EH. The decrease was similar in the right (160.3 ± 56.9 mL/min/m2) and left kidneys (158.7 ± 45 mL/min/m2) . The inulin clearance (Cin) was similar in both kidneys (35.2 ± 12.5 v 33.6 ± 11.6 mL/min/m2) . In addition, in EH, CPAH was negatively correlated with blood pressure (P < .01). In patients with RVH, CPAH of the “stenotic” kidney was reduced (91.5 ± 47.8 mL/min/m2) as well as Cin (22.9 ± 9.3 mL/min/m2). In contrast a significant increase in CPAH (194.1 ± 63.8 mL/ min/m2) and Cin (47.6 ± 12.6 mL/min/m2) was observed in the contralateral kidney. Kidney function (CPAH and Cin) was not correlated with blood pressure in the “stenotic” kidney. The CPAH and Cin of the nonstenotic kidney were positively and significantly correlated with systemic arterial pressure (P < .001). The Cin was positively correlated with CPAH in all kidneys in RVH or in EH. However, in the contralateral kidney of RVH, a significant upward resetting of the correlation was observed. The Cin/CPAH was increased in the stenotic kidney (25.7 ± 7.6%), as well as in the contralateral kidney (25.6 ± 6.2%). The increased filtration fraction (FF) of the “stenotic” kidney and the kidneys in EH was related to a relative increase or conservation of Cin, whereas the high FF of the contralateral kidney in RVH was due to an absolute increase in Cin. Therefore, the hemodynamic response of the contralateral kidney differs from that observed in EH. The “hyperfiltration” of the contralateral kidney was accompanied by a steeper decline of Cin with aging (P < .001). Am J Hypertens 1989;2:244-252