Diagnosis of renal artery stenosis and renovascular hypertension.

Renovascular hypertension resulting from renal artery stenosis is a potentially curable form of secondary hypertension. Although uncommon in the general hypertensive population, the prevalence of renovascular hypertension rises in selected groups of hypertensive patients. Because of the possibility of cure, screening measures for renal artery stenosis are warranted in hypertensive patients with clinical features suggestive of renovascular disease. For a long time, angiography has been considered the 'gold standard' in screening for arterial stenosis. However, it is invasive and associated with inherent morbidity. Thus, less invasive screening measures with high diagnostic sensitivity and specificity are currently being sought. Magnetic resonance angiography and captopril renal scintigraphy are safer alternatives to angiography, but are expensive and not widely available. Duplex ultrasound is more widely available and provides both anatomic and functional assessment of renal artery stenosis; however, sensitivity and specificity vary considerably among different laboratories. Echo-enhanced duplex ultrasound using the galactose-based agent Levovist(R) produces higher quality images of the renal artery than conventional color Doppler, while significantly reducing mean examination time and improving diagnostic confidence. In addition, Levovist does not compromise the safety of duplex ultrasound. Other advances in Doppler imaging techniques that may improve ultrasound sensitivity and specificity in detection of renal artery stenosis are power Doppler, echo-enhanced harmonic spectral Doppler imaging, and echo-enhanced harmonic power Doppler imaging.