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Is duplex scanning the best screening test for renal artery stenosis?

Screening for renal artery stenosis is indicated in patients with suspected renovascular hypertension or ischemic nephropathy to identify those who could benefit from renal artery interventions. The critical requirements for a clinically useful screening test include safety, low cost, and a high sensitivity or low false-negative rate. Arteriography remains the "gold standard" for the anatomic diagnosis of renal artery disease, but it is unsuitable for screening because of its high cost and invasive nature. Although renal duplex scanning technically is difficult, experienced laboratories have been able to achieve sensitivities and specificities in the range of 93% to 98% for identification of stenoses in the main renal arteries. Renal duplex scanning also provides a method for assessing the renal parenchyma and predicting the clinical outcome of renal revascularization. The principal limitation of renal duplex scanning is failure to identify accessory renal arteries. The finding of one or more widely patent main renal arteries makes ischemic nephropathy unlikely, because this condition results from "total" renal ischemia. However, renovascular hypertension can be present with normal main renal arteries when there are isolated stenoses involving accessory renal arteries, so further testing may be indicated in selected hypertensive patients with normal main renal arteries by duplex scanning. Currently, duplex scanning in a qualified vascular laboratory arguably is the best screening test for renal artery stenosis. Other methods for assessing the renal arteries, particularly spiral computed tomography and magnetic resonance angiography, are evolving rapidly and also may play a role in screening of selected patients.