[Usefulness of captopril test in diagnosis of renal artery stenosis and congenital small kidney in arterial hypertension].

We studied 45 hypertensive subjects to evaluate the usefulness of captopril test for identifying renal artery stenosis and small congenital kidney with the hypoplasia of the renal artery. In 18 hypertensives with hippuran renogram indicating renovascular disease, and in 27 essential hypertensives, the plasma renin activity (PRA) responses to an oral test dose (50 mg) of captopril were studied. A 60-minute post captopril PRA increase of 150% (or 400% if baseline PRA less than 3 ng/ml/h) was considered as positive. Digital venous angiography was performed in all cases. In the group of 18 subjects small congenital kidney in 7, and renal artery stenosis in 11 subjects were detected by angiography. Captopril test resulted negative in all patients with small congenital kidney (mean PRA% increase 58). The test identified 7 of the 11 renal artery stenoses (mean PRA% increase 477), sensitivity and specificity were 64% and 100% respectively. In the essential hypertensives-group, mean PRA% increase was 122; there were three false positives, and both sensitivity and specificity were 88%. This study demonstrates that the PRA response to oral captopril test is a useful screening test for distinguishing small congenital kidney from renal artery stenosis and for identifying the latter in hypertensive patients.