Assessment of renal artery stenosis: Side-by-side comparison of angiography and duplex ultrasound with pressure gradient measurements

Aims: A ratio of distal renal pressure to aortic pressure (P _d/P_a) <0.90 can be considered a threshold for defining a significant renal artery stenosis (RAS). The aim of this study was to compare renal angiography (QRA) and colour duplex ultrasound (CDUS) to pressure measurements in assessing RAS. Methods and results: In 56 RAS, percent diameter stenosis (DS_angio), minimal luminal diameter (MLD), Doppler-derived peak systolic velocity (PSV), end-diastolic velocity (EDV), and renal-to-aortic ratio (RAR) were obtained and compared with the P_d/P_a measured with a 0.014" pressure wire. P_d/P_a correlated with angiography- and CDUS-derived parameters. The best correlation was observed with EDV (R = -0.61). To identify stenosis associated with a P _d/P_a < 0.90, the diagnostic accuracy of DS _angio > 50%, MLD < 2 mm, PSV > 180 cm/s, EDV > 90 cm/s and RAR > 3.5 were, respectively, 60%, 77%, 45%, 77% and 79%, yet, with a high proportion of false positives (38%, 15%, 55%, 11% and 15%, respectively) indicating an overestimation of the severity of the RAS by both QRA and CDUS. New cut-off values for QRA- and CDUS-derived indices were proposed. Conclusion: Generally accepted QRA and CDUS-derived indices of RAS severity overestimate the actual severity of RAS. This 'overdiagnosis' is likely the main cause of the disappointing results of renal angioplasty for renovascular hypertension.