Duplex imaging for the detection of renal artery stenosis.

To determine the accuracy of ultrasonic duplex scanning in detecting and classifying renal artery stenosis, we compared the results of duplex scanning with arteriograms in 41 patients with a total of 74 arteries available for comparison. By using a peak systolic velocity of more than 180 cm/s, duplex scanning was able to discriminate between normal and diseased renal arteries with a sensitivity of 95% and a specificity of 90%. Since blood flow velocity across an area of narrowing will increase is roughly proportional to the degree of narrowing, it appeared that the ratio of peak systolic velocity in the area of stenosis to that in the aorta (RAR) of greater than 3.5 predicted the presence of a more than 60% diameter reduction of the renal artery. Using a RAR of 3.5, duplex scanning agreed in 44 renal arteries the sensitivity was 92%. In the 26 renal arteries in which the lesions were less than 60% by arteriography, duplex scanning agreed in 16 arteries and correctly detected an area of focal narrowing in nine of the 10 remaining vessels. Ten of the 11 occluded renal arteries were correctly identified by duplex scanning. Duplex scanning identified the location of the renal artery stenosis with an accuracy of 95%. We believe the data shows that duplex scanning is an accurate method of detecting renal artery stenosis and provides a suitable method of estimating the degree of narrowing.