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.