Renal vein renin sampling in essential hypertension using hydralazine and the tourniquet test

The results of renal vein renin sampling were assessed in 40 patients who had uncomplicated essential hypertension. All had normal creatinine clearance, intravenous pyelography, and arteriography. During sampling, renin release was stimulated in 29 patients with intravenous hydralazine and in 11 with the tourniquet blood trapping test. Simultaneous sequential renal vein samples were drawn over a 30-minute period. Positive renal vein renin ratios (greater than or equal to 1.5) were seen in 52% of the hydralazine group at 0 minutes and in 69% post-hydralazine. In the tourniquet group, 27% had a positive ratio at 0 minutes as compared with 64% post-tourniquets. A significant difference was found in renal vein plasma renin activity between the two kidneys (p greater than or equal to .0001). The asymmetry of renal vein renin activity and the large renal vein renin ratios in these two groups suggest the presence of true differences in renin secretion. These differences may be due to focal nephrosclerosis. The therapeutic significance of a positive renal vein renin ratio in the hypertensive patient should be determined in conjunction with arteriography.