Can intrarenal duplex waveform analysis predict successful renal artery revascularization?

PURPOSE

No currently available noninvasive test can preoperatively predict a successful outcome to renal revascularization. Resistance measurements from the renal parenchyma obtained with duplex sonography reflect the magnitude of intraparenchymal disease, and patients with extensive intrarenal disease may respond less favorably to revascularization. To address this question, we reviewed our (primarily) operative experience in patients undergoing renal artery revascularization, and compared the blood pressure (BP) and renal function response with resistance measurements obtained from the kidney both before and after revascularization.

METHODS

During a 56-month period, 31 consecutive renal artery revascularizations (25 surgical and 6 percutaneous angioplasties) were performed in 23 patients (21 atherosclerotic, 2 fibromuscular dysplasia). Duplex sonography was performed in each patient before and after revascularization, and parenchymal diastolic/systolic (d/s) ratios were calculated. BP and renal function response to intervention were compared with measurements of intrarenal flow patterns before and after revascularization.

RESULTS

Mean parenchymal peak systolic velocity was significantly higher after repair in all patients (pre-repair: 19.5 +/- 1.3, postrepair: 27.2 +/- 1.7; P < .0001). Despite this, there were no statistical differences between preoperative and postoperative parenchymal d/s ratios. A favorable (cured or improved) BP response was seen in 81% (17 of 21) of revascularizations performed for hypertension. Among these successes, parenchymal d/s ratios were in the normal range (ie, > or = 0.30) both before and after repair (mean prerepair: 0.34 +/- 0.03, mean postrepair: 0.31 +/- 0.03; not significant). In 4 patients in which BP failed to improve after intervention, the d/s ratio was abnormal before surgery (< 0.3), and remained so after revascularization (mean preoperative d/s ratio: 0.18 +/- 0.04, mean postoperative d/s ratio: 0.11 +/- 0.04; P = .003). Mean preoperative parenchymal d/s ratios were significantly higher in all patients with a successful BP response when compared with failures (P = .048). Similarly, among patients with single artery repairs, mean preoperative d/s ratios approached significance in successes vs. failures (success: 0.40 +/- 0.03, failure: 0.21 +/- 0.03; P = .054). A decrease in serum creatinine greater than or equal to 20% was seen in 8 of 18 patients (44%) with ischemic nephropathy. These patients also had normal d/s ratios preoperatively (mean 0.39 +/- 0.04), whereas the 10 patients who failed to improve had significantly lower ratios (mean 0.24 +/- 0.03; P = .041). Kidney length did not correlate with d/s ratio.

CONCLUSION

Although we do not believe that duplex sonographic measurement of intrarenal flow patterns alone is an accurate means of assessing main renal artery occlusive disease, the resistive indices seem to reflect the magnitude of intraparenchymal disease, and thus may provide important prognostic information for patients undergoing surgical revascularization. Our data suggest that a preoperative d/s ratio below 0.3 correlates with clinical failure relative to BP and renal function responses.