Observations on the use and limitations of renal vein renins in hypertensive patients.

From our consecutive series of renal vein renin studies in 170 patients with kidney disorders and hypertension, we present those cured by surgical correction of a unilateral renal artery stenosis during the period 1973--75. The renin secretion patterns of these patients range between no demonstrable abnormality, even with a stimulating procedure using dihydralazine 7.5 i.v., and massive renin secretion already during basal conditions. Thus, the renin secretion may not be increased even after stimulation in some patients with durable unilateral renovascular hypertension. This fact may be explained by the rise of the systemic blood pressure, eventually maintained by sodium and water retention and accompanied by adaptive changes in the contralateral kidney. The perfusion pressure is thereby kept normal in the affected kidney, eliminating a stimulus for renin secretion. It is likely that many cases of renovascular hypertension pass through an early stage where no involvement of the renin-angiotensin system may be discovered. Of course, these patients will also benefit from surgery. The conclusion is that renin studies for diagnostic purposes should be performed when patients are on treatment and kept normotensive for some time, and that an additional challenge of the perfusion pressure, i.e., by use of dihydralazine, intravenously should be performed.