Screening for Renal Artery Stenosis: Are Scans More Accurate Than Clinical Criteria?

Deciding which patients with hypertension to investigate for renal artery stenosis remains one of the most perplexing and controversial decisions facing the internist. No screening test has been sufficiently accurate, inexpensive, noninvasive, reproducible, and adequately validated in practice settings to be accepted universally as a screening procedure. Ideally, the first step in diagnosis is to identify a group of patients with a prevalence of renal artery stenosis that is high enough to justify screening, the second step is to select a test with a high sensitivity, and the third step is to perform arteriography in patients who have positive test results. However, scrutiny of this apparently reasonable process shows that it has been heretofore unsuccessful.

Several important, recent articles have prompted a reevaluation of screening tests for renal artery stenosis. More than 5 years ago, several relatively large, well-controlled studies evaluated the effectiveness of two tests in screening for renal artery stenosis in highly selected, high-prevalence groups: angiotensin-converting enzyme (ACE) inhibitor-induced stimulation of plasma renin activity and changes in the renal scintigram assessed by nuclear medicine techniques. Both tests probably detect a similar physiologic response to ACE inhibitors in functionally substantial renal artery stenosis, namely, a reduction in kidney glomerular filtration rate. An ACE inhibitor-induced decrease in glomerular filtration rate leads to a macula densa-stimulated increase in plasma renin activity (that is, a positive result on a plasma renin activity test after captopril therapy) and a reduction in the rate of clearance of radioactive tracer from the kidney (that is, a positive result on ACE inhibitor scintigraphy). Accordingly, it is not surprising that both tests, under ideal circumstances, yielded similar sensitivities (90% to 95%, with higher specificities for ACE inhibitor scintigraphy than for the plasma renin activity test [1]).

However, the past year has seen the publication of larger …