CAN INTRARENAL DUPLEX WAVE-FORM ANALYSIS PREDICT SUCCESSFUL RENAL-ARTERY REVASCULARIZATION

Purpose:No currently available noninvasive test can preoperatively pre dict a successful outcome to renal revascularization. Resistance measu rements from the renal parenchyma obtained with duplex sonography refl ect the magnitude of intraparenchymal disease, and patients with exten sive intrarenal disease may respond less favorably to revascularizatio n. To address this question, we reviewed our (primarily) operative exp erience in patients undergoing renal artery revascularization, and com pared the blood pressure (BP) and renal function response with resista nce measurements obtained from the kidney both before and after revasc ularization. Methods: During a 56-month period, 31 consecutive renal a rtery revascularizations (25 surgical and 6 percutaneous angioplasties ) were performed in 23 patients (21 atherosclerotic, 2 fibromuscular d ysplasia). Duplex sonography was performed in each patient before and after revascularization, and parenchymal diastolic/systolic (d/s) rati os were calculated. BP and renal function response to intervention wer e compared with measurements of intrarenal flow patterns before and af ter revascularization. Results: Mean parenchymal peak systolic velocit y was significantly higher after repair in all patients (pre-repair: 1 9.5 +/- 1.3, postrepair: 27.2 +/- 1.7; P < .0001). Despite this, there were no statistical differences between preoperative and postoperativ e parenchymal d/s ratios. A favorable (cured or improved) BP response was seen in 81% (17 of 21) of revascularizations performed for hyperte nsion. Among these successes, parenchymal. d/s ratios were in the norm al range tie, greater than or equal to 0.30) both before and after rep air (mean pre-repair: 0.34 +/- 0.03, mean postrepair: 0.31 +/- 0.03; n ot significant). In 4 patients in which BP failed to improve after int ervention, the d/s ratio was abnormal before surgery (<0.3), and remai ned so after revascularization (mean preoperative d/s ratio: 0.18 +/- 0.04, mean postoperative d/s ratio: 0.11 +/- 0.04; P = .003). Mean pre operative parenchymal d/s ratios were significantly higher in all pati ents with a successful BP response when compared with failures (P = .0 48). Similarly, among patients with single artery repairs, mean preope rative d/s ratios approached significance in successes vs, failures (s uccess: 0.40 +/- 0.03, failure: 0.21 +/- 0.03; P = .054). A decrease i n serum creatinine greater than or equal to 20% was seen in 8 of 18 pa tients (44%) with ischemic nephropathy. These patients also had normal d/s ratios preoperatively (mean 0.39 +/- 0.04),whereas the 10 patient s who failed to improve had significantly lower ratios (mean 0.24 +/- 0.03; P = .041). Kidney length did not correlate with d/s ratio. Concl usion: Although we do not believe that duplex sonographic measurement of intrarenal flow patterns alone is an accurate means of assessing ma in renal artery occlusive disease, the resistive indices seem to refle ct the magnitude of intraparenchymal disease, and thus may provide imp ortant prognostic information for patients undergoing surgical revascu larization. Our data suggest that a preoperative d/s ratio below 0.3 c orrelates with clinical failure relative to BP and renal function resp onses.