Renal artery stenosis: evaluation with color Doppler flow imaging. Renal artery stenosis (RAS) is the most common correctable cause of hypertension. The current study was undertaken to evaluate the usefulness of color Doppler flow imaging as a screening examination in the detection of significant RAS. Fifty-five kidneys in 30 patients were examined with aortography and color Doppler flow imaging in a double-blind fashion. The peak systolic velocity (PSV) in the renal artery, the renal-aortic ratio (RAR) (ie, the ratio of the PSV in the renal artery to the PSV in the aorta), and the renal artery resistive index were determined and compared with the percentage of stenosis as determined with angiography. Ultrasound (US) criteria used to diagnose RAS were (a) an RAR of 3.5 or greater and/or (b) a renal artery PSV of greater than 100 cm/sec. Doppler tracings were obtained in 25 (69%) of 36 kidneys with a patent single renal artery. RAR and PSV each yielded a sensitivity of 0% in the diagnosis of RAS. Doppler tracings were obtained in three (50%) of six occluded renal arteries. Accessory arteries were present in 13 (24%) of 55 kidneys, but none were visualized with color Doppler flow imaging. The authors conclude that with current technical capability, color duplex US is not an adequate screening method for the detection of RAS. 