New intrarenal echo-Doppler velocimetric indices for the diagnosis of renal artery stenosis

We aimed at comparing the positive and negative predictive values (PPV, NPV) of several intrarenal velocimetric indices for revealing the presence of renal artery stenosis (RAS) among hypertensive patients who underwent a renal angiography for the clinical suspicion of renovascular hypertension. In 106 patients (200 kidneys), the pulsatility index (PI) and resistive index (RI), the acceleration time (AT), and the mean systolic acceleration (ACCsys) were evaluated. In addition, the maximal systolic acceleration (ACCmax), that is, the maximal slope of the acceleration phase, and the maximal acceleration index (AImax), that is, the ratio between ACCmax and the relative peak systolic velocity, were calculated. On angiography, we found that 56 (28%) of the 200 arteries had a greater than 60% RAS. PI and RI had an NPV below 75%, whereas AT, ACCsys, ACCmax, and AImax had an NPV always above 95%. However, ACCmax, and AImax, at their best cutoff limits, had higher PPV than ACCsys and AT (60 and 70% vs 45 and 51%, respectively). Thus, in a cohort of patients with a high prevalence of RAS, PI and RI failed to reach an NPV adequate for a screening test. In contrast, all the acceleration indices we tested had a sufficiently high NPV but AImax appears superior to the others because of higher PPV. We propose the evaluation of AImax as an additional screening test in patients with hypertension and the clinical suspicion of RAS.