Duplex scanning for diagnosis of peripheral arterial disease.

At the beginning of the 1970's, duplex scanning was developed to delineate arteriosclerotic changes in the region of the carotid bifurcation. Technical improvements subsequently enabled duplex scanning for evaluation of the peripheral arterial system, the mesenteric arteries and lastly, the renal arteries and the deep veins. Ultrasonic frequencies between 2.5 and 10 MHz are necessary for image processing. The B-image alone is not sufficient to assess the severity of stenoses, however, it serves as a guide for positioning the sample volume to analyze the segmental changes in velocity. Based on the flow profile, the degree of stenosis is classified as normal, 1 to 19%, 20 to 49%, 50 to 99% and total occlusion. The blood vessels of each leg are divided into seven segments and the results of duplex scanning and concurrently performed angiography in a total of 50 patients were compared. The duplex sonographic results were superior to those obtained with angiography as determined by two independent observers. Angiography remains the decisive method if surgical or angioplastic methods are considered. The angiographic assessment of stenosis severity in one plane only is however a matter regarded with increasing criticism. Consequently, duplex sonographic measurements of the pressure gradient at rest and after vasodilatation have been carried out and hemodynamic relevance specified by the criteria of a pressure gradient of more than 10 mm Hg at rest and 20 mm Hg after injection of papaverine. As compared with sonographic evaluation of aorto-iliac segments, the angiographic assessment yielded a relatively high rate of false positive and false negative findings. Duplex scanning appears to be a meaningful alternative for assessment of stenosis severity.