Duplex ultrasound for identifying renal artery stenosis: direct criteria re-evaluated

Background Renal artery duplex ultrasound (RADUS) is an established method for diagnosis of renal artery stenosis (RAS), but there is no consensus regarding optimal RADUS criteria. Purpose To define optimal cutoff values for RADUS parameters when screening for RAS using intra-arterial trans-stenotic pressure gradient measurement (PGM) as reference. Material and Methods The renal arteries of 58 consecutive patients evaluated for renovascular hypertension were examined by RADUS and PGM. Conclusive measurements with both methods were obtained in 76 arteries. Hemodynamically significant RAS was defined as PGM ≥15 mmHg and was found in 43 of the 76 arteries. RADUS parameters included renal artery peak systolic velocity (PSV) and the renal–aortic ratio (RAR) of flow velocities. Receiver operating characteristic curves (ROCs) and Youden’s index were used to calculate optimal RADUS criteria for RAS. Results When traditional RADUS criteria for RAS were used, with a combination of PSV ≥180 cm/s and RAR ≥3.5, the sensitivity was 62% and the specificity was 91%. When RADUS criteria were optimized for sensitivity, then RAR ≥2.6 alone resulted in a sensitivity of 89% and a specificity of 69%. Conclusion The RAR ≥2.6 is a more sensitive criterion than traditional RADUS criteria when screening patients with clinical suspicion of RAS.