What is the role of Ultrasound in diagnosing renovascular hypertension?
Patients with difficult to control severe hypertension are the group most likely to have hypertension on the basis of main renal artery stenosis (RAS). RAS only accounts for up to 5% of all patients with hypertension but is a potentially curable cause of hypertension. US can be used as an initial screening test for main RAS. It has the advantage of being relatively less expensive and not requiring intravenous contrast material to image the main renal arteries as compared to CTA or MRA of the kidneys. However, it has the disadvantages of a higher technical failure rate due to high operator dependence. The normal main renal artery has a rapid systolic upstroke and continuous diastolic flow. Color spectral Doppler findings of main RAS are a PSV in the main renal artery >200 cm/sec and/or a main renal/aortic PSV ratio >3.5. Detection of a parvus tardus waveform (small-amplitude waveform with a prolonged systolic rise) in more distal intrarenal arteries also suggests more proximal main RAS