The role of duplex sonography and angiography in the investigation of carotid artery disease

Some patients with symptomatic carotid stenoses of greater than 70 % benefit from carotid endarterectomy. This study was designed to compare the accuracy of duplex ultrasound with angiography in assessing the degree of carotid stenosis in 73 patients with symptoms of recent carotid territory ischaemia. Ultrasound was found to be most accurate in the group of patients with normal vessels or mild stenoses (0-29 %) when there was 90 % concordance between ultrasound and angiography. Ultrasound was found to be least accurate in the group of patients with severe stenoses (70-99 %) in whom it was more likely to underestimate than to overestimate the degree of stenosis. Only one patient said to have < 30 % stenosis on ultrasonography had a > 70 % stenosis on IADSA. Our results indicate that patients with normal arteries or mild disease shown by ultrasound have a very small chance of having surgically amenable lesions in the neck. Ultrasound is reliable as an exclusory screening test. However, all other stenoses should also be investigated by catheter angiography if surgery is considered. Taking angiography as the reference, only 52 % of patients with severe stenoses,which might be taken as an indication for surgery, were correctly identified on ultrasonography. Ultrasound alone is a poor technique for identifying patients for surgery and a combination of ultrasound screening with angiography for > 30 % stenoses detected by ultrasound is recommended.