Clinical Utility of Resistive Index in the Management of Atherosclerotic Renovascular Disease

Background: This study examines the relationship between renal resistive index (RI) determined by Doppler interrogation of hilar vessels and response to open surgical and percutaneous intervention for atherosclerotic renovascular disease.
Methods: From March 1997 to December 2005, 88 patients had serial renal duplex sonography (RDS), including main renal artery and hilar vessel Doppler interrogation, prior to intervention to treat atherosclerotic renovascular disease (RVD). The cohort consisted of 47 women and 41 men, with a mean age of 68±10 years, who underwent either open operative repair (56 patients) or percutaneous treatment (32 patients). Resistive index (1-[EDV/PSV]) was calculated using Doppler indices from the kidney with the highest peak systolic velocity (PSV). Hypertension response was graded from pre- and post-procedure blood pressure measurements and medication requirements. Renal function response was based on a ≥ 20% change in estimated glomerular filtration rate (EGFR).
Results: Most baseline characteristics were similar in patients undergoing open versus percutaneous repair. Exceptions include: (1) higher mean age in the percutaneous group (72±11 years vs 67±9 years in open group; p=.03); (2) greater mean kidney length in the percutaneous group (11.3±1.3 cm vs 10.7±1.2 cm in open group; p=.04); and (3) greater proportion of patients with RI ≥ 0.8 in the percutaneous group (47% vs 21% in the open group; p=.01). Comorbid conditions, baseline blood pressure and preoperative renal function were not significantly different between groups. With respect to blood pressure response, cure was achieved in 4%, improvement in 48% and no change in 48% of patients. Blood pressure response was better in the open group compared to the percutaneous group (59% cured/improved in open vs. 41% in percutaneous), but this did not reach statistical significance. Multivariate analysis showed no correlation between resistive index and blood pressure response in either the open or percutaneous group. Renal function was improved in 33%, unchanged in 45%, and worsened in 22% following intervention. Graded renal function response was better following open intervention compared to percutaneous therapy (39% cured/improved in open group vs. 22% in percutaneous), but once again did not reach statistical significance. There was a significantly greater change in EGFR from pre- to post-procedure with open compared to percutaneous repair (mean EGFR change 6.3±17.6 in open vs. -3.4±16.1 in percutaneous; p=.01). In the percutaneous group, an RI of ≥ 0.8 vs < 0.8 was associated with a differential response to therapy. In patients with an RI ≥ 0.8 there was a 12.0±4.8 ml/min/1.73m² decrease in postop EGFR (p=.02). Patients with open repair had no correlation between renal function response and RI (RI ≥ 0.8 associated with 7.4±5.9 ml/min/1.73m² decrease in EGFR; p=.21).
Conclusion: In this group, resistive index estimated from hilar renal artery analysis was associated with renal function response after percutaneous intervention, but not blood pressure response. No relationship was observed between resistive index and renal function or blood pressure response following open operative repair of atherosclerotic renal artery disease.