Renal artery revascularization: predictive value of kidney length and volume weighted by resistive index.

Objective: The purpose of this study was to evaluate the usefulness of renal length, volume, and resistive index measurements at Doppler ultrasound and MR angiography in predicting improvement after renal angioplasty.
Materials and Methods: Fifty-one patients underwent Doppler ultrasound examinations and MR angiography before percutaneous transluminal renal angioplasty. Renal length, total and cortical volumes, and resistive index were calculated. Combinations of length, volume, and resistive index measurements were correlated with improvement in blood pressure and renal function after percutaneous transluminal renal angioplasty. Thresholds for improving patient selection were chosen after analysis of receiver operating characteristics curves.
Results: Lower total and cortical volumes on MR angiograms and shorter kidney length on Doppler ultrasound images were found among patients with successful blood pressure control (p = 0.042, p = 0.035, and p = 0.016, respectively). Renal length measured with Doppler ultrasound and cortical volume measured with MR angiography weighted by resistive index were the best predictive factors (p = 0.004, p = 0.006). Using a threshold of renal length-resistive index product less than 7 cm, therapeutic response was predicted with a sensitivity of 87% and specificity of 50%, whereas with a threshold value of 52 mL/m(2) for cortical renal volume-resistive index product divided by body surface area, sensitivity of 86% and specificity of 50% were obtained.
Conclusion: Renal length and volume combined with resistive index measurements appear to be predictive of therapeutic response after percutaneous transluminal renal angioplasty.