Diagnosis of renovascular disease by extra- and intrarenal Doppler parameters

It is still a matter of debate as to which parameters should be used for noninvasive diagnosis of renovascular disease by renal Doppler sonography (RDS). The accuracy of RDS in the detection of renal artery stenosis (RAS) was tested in 95 consecutive, moderate to severe hypertensive patients (I-II World Health Organization [WHO] stages). Reno-aortic ratio (RAR) for peak systolic velocity (PSV) was also calculated to assist in the diagnosis of significant (>50%) RAS. Paired receiver-operating characteristic (ROC) analysis was plotted for evaluating the relationship between sensitivity and specificity for each parameter. In a subset of 57 kidneys, the influence of blood pressure and age on intraparenchymal parameters was evaluated. Measurements of maximal peak systolic velocity (PSV) at the site of stenosis, RAR for PSV, and minimum acceleration index in the main renal artery showed high accuracy (areas under the ROC curve 0.97, 0.88, and 0.80, respectively). Among intraparenchymal parameters, early systolic acceleration showed the best area under the ROC curve (0.90), but provided a low positive predictive value (29%) and was significantly influenced by blood pressure (multiple r=0.56; p=0.001). Pulsatility and resistive indices were found to be less powerful as absolute values, and both significantly influenced by blood pressure and age (multiple r = 0.60 and 0.50; p=0.001, p=0.02, respectively). However, interindividual variance of intrarenal indices should be minimized by calculation of side difference, although this procedure would become misleading or impossible in patients with bilateral RAS or a single kidney, respectively. These results support the use of extraparenchymal parameters for noninvasive detection of RAS, and emphasize that intrarenal parameters cannot be considered as absolute values.