Evaluation of renal artery stenosis with hemodynamic parameters of Doppler sonography.

OBJECTIVE: The purpose of this study was to determine the values of the hemodynamic parameters of Doppler sonography in the diagnosis of renal artery stenosis (RAS) (diameter reduction >/=50%) and to investigate their possible influencing factors.

METHODS: Five Doppler parameters, including renal peak systolic velocity (RPSV), renal-aortic ratio (RAR), renal-renal ratio (RRR), renal-segmental ratio (RSR), and renal-interlobar ratio (RIR), were measured in 81 patients before arteriography. Arteries with >/=50% diameter reduction were considered stenosed at renal arteriography. Receiver operating characteristic curve analysis was performed to determine the optimal parameters. The sensitivity, specificity, positive and negative predictive values, and accuracy at various threshold values were calculated.

RESULTS: Sixteen accessory renal arteries (15 normal, one mild stenosis) were identified at arteriography. Of the 153 main renal arteries demonstrated at arteriography, 79 were normal or demonstrated stenosis <50%, 68 demonstrated moderate stenosis (50%-99%), and 6 demonstrated total occlusion. Doppler sonographic examination was technically successful in 91.7% (154/168) of main and accessory renal arteries. The optimal threshold values of RPSV, RAR, RRR, RSR, and RIR were 170 cm/s, 2.3, 2.0, 4.0, and 5.5, respectively. The parameters RPSV, RSR, and RIR showed good diagnostic results with accuracies equal to or greater than 88%, whereas RAR and RRR presented a sensitivity of only 76.47%. The diagnostic accuracies of RPSV, RAR, and RRR were approximately 3% higher after exclusion of the eight patients with abdominal aorta stenosis.

CONCLUSION: It should be feasible and necessary to measure three representative hemodynamic parameters (RAR, RPSV, and RIR or RSR) in the diagnosis of >/=50% RAS. The PSVs in the abdominal aorta and renal artery can be affected by factors other than RAS, which may decrease the accuracy of RAR. However, post-PSV ratios are minimally affected by PSV in the abdominal aorta or by an equal proportional change in PSVs in the renal artery trunk and its intrarenal renal arteries; therefore, use of post-PSV ratios dramatically overcomes some limitations of RAR.