Volume 69, Issue 3, Pages 580-587 (February 2006) New intrarenal echo-Doppler velocimetric indices for the diagnosis of renal artery stenosis  M. Bardelli, F. Veglio, E. Arosio, A. Cataliotti, E. Valvo, A. Morganti  Kidney International  Volume 69, Issue 3, Pages 580-587 (February 2006) DOI: 10.1038/sj.ki.5000112 Copyright © 2006 International Society of Nephrology Terms and Conditions

Figure 1 (a) Analysis of the Doppler spectra. From this, the following hemodynamic parameters can be derived: PSV, EDV, the averaged mean velocity (Vmean) AT taken as the time from the beginning to the peak of the systole; ΔVsys indicates the velocity gradient between the foot and the peak of the systolic phase. From these parameters, the conventional distal Doppler velocimetric indices, that is, PI, RI, and the mean acceleration ACCsys, are calculated as reported in the text. (b) Heterogeneous velocity cycle slope morphologies that can be found in normal and stenotic renal arteries. The type ‘A’ morphology has a constant systolic acceleration until the systolic peak and it is characteristic of a normal hemodynamic pattern. However, in normal and stenotic arteries also the ‘B1’ and ‘B2’ morphologies can be found, characterized respectively by a double peak during the systolic acceleration and by a shoulder that divides the early steeper acceleration from the late, less steep phase. The type ‘C’ morphology is characterized by a flattered cycle with a rounded systolic shape and is typical of a post-stenotic flow regimen. (c) Illustration of how the cycle morphologies can affect the calculation of velocimetric indices. It is obvious that in normal arteries both B type morphologies can cause a delayed AT resulting in dampened ACCsys, mimicking a condition similar to that found in stenotic arteries (type C morphology). (d) Illustration of how the new indices proposed in this study can improve the diagnostic accuracy in arteries with type ‘B’ morphology. Focusing on the estimation of the acceleration in the early systolic phase, we derived the maximal systolic acceleration (ACCmax=ΔVmax/ATmax) defined as the mean slope of the systolic acceleration until any significant change of its first derivative has been introduced (white arrow). Moreover, by correcting the acceleration for the relative absolute velocity regimen, which may differ at different levels of the renal vascular tree, we derived the maximal acceleration index (AImax=ACCmax/PSV). Kidney International 2006 69, 580-587DOI: (10.1038/sj.ki.5000112) Copyright © 2006 International Society of Nephrology Terms and Conditions

Figure 2 Distribution of the 72 stenotic kidneys with respect to the site, type, and severity of RAS. As expected, there was a prevalence of fibromuscular RAS in the renal artery trunk in comparison with atherosclerotic RAS, which was more frequently located at the ostium; between the two types of RAS, there were no significant differences in the severity of the stenosis. Kidney International 2006 69, 580-587DOI: (10.1038/sj.ki.5000112) Copyright © 2006 International Society of Nephrology Terms and Conditions

Figure 3 Scatter distribution of the pulsatility and resistive indices (PI and RI) and their mean (±s.d.) values sampled in parenchymal arteries in kidneys without RAS and with significant and not significant RAS. A large overlapping between the three subgroups of arteries is evident. Kidney International 2006 69, 580-587DOI: (10.1038/sj.ki.5000112) Copyright © 2006 International Society of Nephrology Terms and Conditions

Figure 4 Histogram distribution of ACCsys, AT, ACCmax, and AImax in the 144 renal arteries with no RAS (n=128) and with not significant RAS (n=16). The gray area includes the false positive studies, which are clearly reduced with ACCmax and even more so with AImax (abbreviations are as in the text). Kidney International 2006 69, 580-587DOI: (10.1038/sj.ki.5000112) Copyright © 2006 International Society of Nephrology Terms and Conditions

Figure 5 Scatter distribution of (a) ACCsys, (b) AT, (c) ACCmax, and (d) AImax values sampled in stenotic and non-stenotic kidneys in the parenchymal arteries. The dotted line represents the ideal cutoff values calculated for each index with the ROC curve analysis, whereas the gray and less gray areas include the false negative and false positive studies subdivided according to the cycle morphology curve described in Figure 1. For all indices, the rate of false negatives is obviously lower than that of PI and RI shown in Figure 3. Note that the majority of the false positive studies are attributable to arteries with type B cycle morphology and that erroneous diagnoses are reduced with ACCmax and AImax (abbreviations are as in the text). Kidney International 2006 69, 580-587DOI: (10.1038/sj.ki.5000112) Copyright © 2006 International Society of Nephrology Terms and Conditions

Figure 6 Values of ACCsys, AT, ACCmax, and AImax sampled at the pre-hilar and parenchymal sites. For all indices except AImax, there were significant differences between (mean±s.d.) the two sites of sampling as a result of the hemodynamic gradient along the renal circulation. Figures on the vertical axis refer to the units used to calculate the indices shown on the horizontal axis. Kidney International 2006 69, 580-587DOI: (10.1038/sj.ki.5000112) Copyright © 2006 International Society of Nephrology Terms and Conditions