Screening for renovascular disease with captopril-enhanced renography

Changes in renal function caused by angiotensin-converting-enzyme (ACE) inhibitors can be detected on 99mTc-DTPA renography so that DTPA scanning before and after a single dose of captopril can be used to screen for renovascular disease. We have performed captopril-DTPA scans with renal arteriography on 104 patients, of whom 27 had renal artery stenosis, all due to atheroma. Using a 5% fall in divided function or a delay of greater than 15 min in time to peak activity on one side after captopril, or the finding of greater than 90% divided function on one side before captopril as criteria for a positive scan, a sensitivity of 93% and specificity of 70% was achieved. The negative predictive value of the test in our population was 93%. Bilateral improvement in renographic function after captopril was seen in patients with accelerated phase hypertension. The presence of bilateral renal artery disease did not reduce the sensitivity of the test, but sensitivity was reduced (75%) in patients with renal impairment. Clinical characteristics in our patients most strongly associated with renal artery stenosis were abdominal bruit, recurrent left ventricular failure, and peripheral vascular disease. In view of the well-publicized risks of ACE inhibitor therapy, care should be exercised in the use of these agents in such patients.