Plasma Renin Activity in Renovascular Hypertension

Dynamics of plasma renin activity (PRA) in peripheral and renal vein was studied in 22 patients with various types of renovascular hypertension. Significant elevation of resting peripheral vein PRA (PPRA) was observed in 7 out of 8 cases with unilateral main renal artery stenosis (type I). However, PPRA remained normal or slightly elevated in 5 cases with unilateral branch renal artery stenosis (type II), in 5 out of 6 cases with bilateral main renal artery stenosis (type III), and in one with unilateral main renal artery stenosis of the remaining kidney after contralateral nephrectomy. In all cases with type I and II higher renal vein PRA (RPRA) was found on the affected side, while RPRA in type III remained in normal range or slightly elevated on both sides. The ratio of RPRA between higher and lower sides was 1.27±0.10 (SE) in type III. These values were smaller than that of 2.02±0.24 (SE) in type I and II, and were not significantly different from that of 1.20±0.04 (SE) in control group. In statistical analysis of 79 cases including 57 cases reported by other authors, normal PPRA level was found in 69.1% of patients with type III stenosis, while PPRA was normal in only 19.5% Of cases with type I stenosis, and in 50.0% of cases with type II. There was significant difference in frequencies of normal PPRA between type I and III (P<0.001), and also between type I and II (P<0.05), respectively. Dynamics of PRA in renovascular hypertension was in close association with the types of renal arterial abnormality. Patients with renovascular hypertension, irrespective of their resting PPRA, responded to i.v. injection of furosemide and upright position with remarkable increase in renin secretion. This procedure was practically useful for the differential diagnosis of renovascular hypertension.