Experience with renal vein renin ratios in the identification of a pressor kidney

The positive, preoperative recognition of a pressor kidney has many important ramifications, the most important being the ability to predict a reduction in blood pressure following surgical reconstruction or nephrectomy. One hundred forty hypertensive patients were selected for study for renal artery stenosis by measuring the differential plasma renin activity by either radioimmunoassay or bioassay. Bilateral renal vein renin determinations and renal arteriography were made consecutively in supine position and without stimulation of renin secretion. Unilateral or bilateral renal artery stenosis was found in 55 patients (39%). Twenty-eight of the 55 patients (51%) were treated surgically. Eighteen patients (64%) were cured of hypertension and seven (25%) were improved. All but one of the surgically treated patients had renal vein renin ratios of greater than 1.3 on the affected side over the unaffected or less-affected side. Increasing the ratio to greater than 1.5 or greater than 2.0 as a criterion for selection of patients for operation would not have decreased the failure rate. If used as the only criterion, increasing the ratios would have resulted in nonsurgical treatment of up to 50% of the patients cured or improved by surgery. Stimulation of renin secretion, although not used in this study, has been shown by others to more accurately identify a pressor kidney by increasing differential renal vein renin ratios. Although a combination of renin activity with renal plasma flow may lead to more accurate diagnosis, a careful clinical evaluation has not yet been replaced as the best method of selection of the patients for operation.