Critical analysis of renal duplex ultrasound parameters in detecting significant renal artery stenosis

Abstract

Several published studies have reported differing results of renal duplex ultrasound (RDU) imaging in detecting significant renal artery stenosis (RAS) using different Doppler parameters. This study is the largest to date to compare RDU imaging vs angiography and assess various published Doppler criteria. RDU imaging and angiography were both done in 313 patients (606 renal arteries). RAS was classified as normal, <60%, ≥ 60% to 99%, and occlusion. Main outcome measurements included renal peak systolic velocity (PSV), systolic renal-to-aortic ratio (RAR), end-diastolic velocity (EDV), and kidney lengths. The mean PSVs and RARs for normal, <60%, and ≥ 60% stenosis were 173, 236, and 324 cm/s (P < .0001), and 2.2, 2.9, and 4.5, respectively (P < .0001). The PSV cutoff value that provided the best overall accuracy for ≥ 60% stenosis was 285 cm/s, with a sensitivity, specificity, and overall accuracy of 67%, 90%, and 81%, respectively. The RAR cutoff value with the best overall accuracy for ≥ 60% stenosis was 3.7, with a sensitivity, specificity, and overall accuracy of 69%, 91%, and 82%, respectively. A PSV of ≥ 180 cm/s and RAR of ≥ 3.5 had a sensitivity, specificity, and overall accuracy of 72%, 81%, and 78% in detecting ≥ 60% stenosis. A PSV of ≥ 200 cm/s with an RAR of ≥ 3.5 had a sensitivity, specificity, and overall accuracy of 72%, 83%, and 78% in detecting ≥ 60% stenosis. A receiver operator characteristic (ROC) curve analysis showed that the PSV and RAR were better than the EDV in detecting ≥ 60% stenosis: PSV area under the curve (AUC) was 0.85 (95% confidence interval [CI], 0.81-0.88), EDV AUC was 0.71, and RAR AUC was 0.82 (PSV vs EDV, P < .0001; PSV vs RAR, P = .075; EDV vs RAR, P < .0001). A PSV of 285 cm/s or RAR of 3.7 alone were better than any combination of PSVs, EDVs, or RARs in detecting ≥ 60% stenosis. The mean kidney length was 10.4 cm in patients with ≥ 60% stenosis vs 11.0 cm in patients with <60% stenosis (P < .0001). Twelve percent of patients with ≥ 60% stenosis had a kidney length of ≤ 8.5 cm vs 4% in patients with <60% stenosis (P = .0003), and 5.6% (34 of 606) had accessory renal arteries on angiography, with six detected on RDU imaging. The presence of accessory renal arteries, solitary kidneys, or renal fibromuscular dysplasia had no influence on overall accuracy of using PSV values for detecting ≥ 60% stenosis. A PSV of 285 cm/s or an RAR of 3.7 alone can be used in detecting ≥ 60% RAS. Previously published data must be validated in individual vascular laboratories.