The decrease of blood pressure and the increase of plasma renin activity (PRA) after oral administration of captopril was evaluated in 104 consecutive hypertensive out-patients in whom the morphology of the renal arteries and parenchyma was assessed thanks to an intravenous digitalized angiography. Twenty five of these patients were excluded because of a natriuresis less than 50 mmol/24 h or non discontinuation of their treatment; 50 of these patients were classified as essential hypertension, 12 had renovascular disease (10 unilateral stenosis 2 of which significant; 2 bilateral significant stenosis); 9 had unilateral small kidneys (4 significant). The significance was ascertained on the PRA in the renal veins and/or the decrease of hypertension after surgery. The decrease of blood pressure after captopril was not different between the various groups. The increase after captopril of PRA was higher in unilateral significant lesions. However the highest post captopril PRA value was found in the essential hypertension group so that renovascular diseases could not be screened by higher post captopril PRA values. However taking into account that these latter were decreasing with age, a better discrimination of significant unilateral disease was possible in the hypertensive patients above 40 years of age. Furthermore once the diagnosis of unilateral kidney disease is established by radiological investigation, the captopril test allows to predict unilateral hypersecretion of renin with a sensitivity of 100% and a specificity of 78%.
In conclusion: the captopril test does not allow to screen the non selected hypertensive patients for an efficient radiological investigation by intravenous digitalized angiography but may help to select the patients with unilateral renal disease for the renal venous PRA evaluation.