Noninvasive assessment of renal artery stenosis: Current imaging protocolsand future directions in ultrasonography

Doppler ultrasound is one of many modalities that have been evaluated for t he detection of renal artery stenosis. The lack of standardization in exami nation protocols and diagnostic criteria, as well as the wide differences i n reported accuracy among different laboratories have, however, prevented u niversal acceptance of this technique as a reliable screening test for rena l artery stenosis. The recent introduction of ultrasound contrast agents ha s substantially expanded the potential of color Doppler ultrasound. The use of microbubble echoenhancers in combination with harmonic Doppler imaging has been shown to improve diagnostic confidence by improving the operator's ability to visualize the renal arteries, and to significantly reduce the n umber of equivocal examinations. Moreover, contrast-enhanced Doppler ultras ound can provide functional information through analysis of renal time-inte nsity wash in/wash out curves. State-of-the-art contrast-enhanced Doppler u ltrasound seems to have the potential to become a useful screening test for patients at risk from renovascular hypertension.