Diagnosis and evaluation of renovascular hypertension. Indications for therapy. Renovascular hypertension is caused by two distinct conditions with different causes, fibromuscular dysplasia and atheroma. Diagnosis of the former is both simpler and more rewarding, whereas atheromatous lesions of the renal artery may be secondary to essential hypertension. It is therefore important to establish existence of functional renal ischemia as well as an anatomical lesion. Universal screening of all hypertensive patients is not recommended because of the relatively low prevalence of the disease and insufficient accuracy of available screening tests. When renovascular hypertension is clinically suspected, an oral captopril test is the most reliable office screening test. After this, digital subtraction angiography with renal vein renins or captopril renography are appropriate steps. However, the latter procedure, while promising, requires further evaluation. Duplex scanning of the renal arteries also comes into this category. Arteriography is done last, so that if renal ischemia is indicated, angioplasty can be attempted at the same time as arteriography. 