Renal duplex sonography after treatment of renovascular disease

Renovascular Disease and Mesenteric Vascular Disease

Renal artery stenosis is caused by atherosclerosis and fibromuscular dysplasia and is associated with ischemic nephropathy, renovascular hypertension, and accelerated cardiovascular disease. Routine screening for renal artery stenosis is not recommended but is reasonable in patients who have rapid onset of hypertension, resistant hypertension, progressive renal insufficiency, recurrent pulmonary edema, or repeat admissions for heart failure. Acute mesenteric ischemia is caused by arterial embolism or thrombosis, mesenteric venous thrombosis, or nonocclusive mesenteric ischemia, whereas chronic mesenteric ischemia is most often caused by arterial obstruction. This article reviews the epidemiology, pathophysiology, diagnosis, and management of these two conditions.

To Stent or Not to Stent? Update on Revascularization for Atherosclerotic Renovascular Disease

Renal artery stenosis (RAS) is increasingly encountered in clinical practice. The two most common etiologies are fibromuscular dysplasia (FMD) and atherosclerotic renal artery disease (ARAS), with the latter accounting for the vast majority of cases. Significant RAS activates the renin-angiotensin-aldosterone system and is associated with three major clinical syndromes: ischemic nephropathy, hypertension, and destabilizing cardiac syndromes. Over the past two decades, advancements in diagnostic and interventional techniques have led to improved detection and the widespread use of endovascular renal artery revascularization strategies in the management of ARAS. However, renal artery stenting for ARAS remains controversial. Although several studies have demonstrated some benefit with renal artery revascularization, this has not been to the extent anticipated or predicted. Moreover, these trials have significant flaws in their study design and are hampered with inherent bias which make their interpretation challenging. In this review, we evaluate the existing body of evidence and offer an approach to the management of patients with ARAS in light of the current literature. From the data provided, identification of subgroup of patients, namely, those with a hemodynamically significant RAS in the context of progressive renal insufficiency and/or deteriorating arterial hypertension, seems possible and may derive clinical benefit from ARAS stent revascularization. Appropriate patient selection is therefore the key and more robust studies are required.

Early duplex predicts restenosis after renal artery angioplasty and stenting

OBJECTIVE

To examine the relationship between early renal duplex sonography (RDS) and restenosis after primary renal artery percutaneous angioplasty and stenting (RA-PTAS).

METHODS

Consecutive patients undergoing RA-PTAS for hemodynamically significant atherosclerotic renal artery stenosis with hypertension and/or ischemic nephropathy between September 2003 and July 2010 were identified from a prospective registry. Patients had renal RDS pre-RA-PTAS, within 1 week of RA-PTAS and follow-up RDS examinations after the first postoperative week for surveillance of restenosis. Restenosis was defined as a renal artery peak systolic velocity (PSV) ≥ 180 cm/s on follow-up RDS. Associations between RDS and restenosis were examined using proportional hazards regression.

RESULTS

Eighty-three patients (59% female; 12% nonwhite; mean age, 70 ± 10 years; mean pre-RA-PTAS PSV, 276 ± 107 cm/s) undergoing 91 RA-PTAS procedures comprised the sample for this study. All procedures included a completion arteriogram demonstrating no significant residual stenosis. Mean follow-up time was 14.9 ± 10.8 months. Thirty-four renal arteries (RAs) demonstrated restenosis on follow-up with a median time to restenosis of 8.7 months. There was no significant difference in the mean PSV pre-RA-PTAS in those with and without restenosis (287 ± 96 cm/s vs 269 ± 113 cm/s; P = .455), and PSV pre-RA-PTAS was not predictive of restenosis. Within 1 week of RA-PTAS, mean renal artery PSV differed significantly for renal arteries with and without restenosis (112 ± 27 cm/s vs 91 ± 34 cm/s; P = .003). Proportional hazards regression analysis demonstrated increased PSV on first post-RA-PTAS RDS was significantly and independently associated with subsequent restenosis during follow-up (hazard ratio for 30 cm/s increase, 1.81; 95% confidence interval, 1.32-2.49; P = .0003). There was no difference in pre- minus postprocedural PSV in those with and without restenosis on follow-up (175 ± 104 cm/s vs 179 ± 124 cm/s; P = .88), nor was this associated with time to restenosis. Best subsets model selection identified first postprocedural RDS as the only factor predictive of follow-up restenosis. A receiver-operating characteristic curve was examined to assess the first week PSV post-RA-PTAS most predictive of restenosis during follow-up. The ideal cut point for RA-PSV was 87 cm/s or greater. This value was associated with a sensitivity of 82.4%, specificity of 52.6%, and area under the receiver-operating characteristic curve of 69.3%. Increased first postprocedural RA-PSV was predictive of lower estimated glomerular filtration rate in the first 2 years after the procedure (-1.6 ± 0.7 mL/min/1.73 m(2) lower estimated glomerular filtration rate per 10 cm/s increase in RA-PSV; P = .010).

CONCLUSIONS

Early renal artery PSV within 1 week after RA-PTAS predicted renal artery restenosis and lower postprocedure renal function. Recurrent stenosis demonstrated no association with absolute elevation in PSV prior to RA-PTAS nor with the change in PSV after RA-PTAS. These data suggest that detectable differences exist in renal artery flow parameters following RA-PTAS that are predictive of restenosis during follow-up but are not apparent on completion arteriography or detectable by intra-arterial pressure measurements. Further study is warranted.

Renovascular disease in children and adolescents

PURPOSE

This retrospective review describes the surgical management of renovascular disease in 25 consecutive children and adolescents with severe hypertension.

METHODS

Patients </=21 years of age (mean age, 11.6 +/- 5.4 years; 12 females, 13 males) underwent repair of 34 renal arteries (RAs), and their management forms the basis of this report. Early and late blood pressure responses were adjusted for gender, age, and height. RA repair was evaluated by angiography, renal duplex sonography (RDS) scanning, or both. Primary patency and survival were estimated by product-limit methods.

RESULTS

Thirty-four RAs among 32 kidneys were repaired. Bilateral renal RA disease to a solitary kidney was present in nine patients. RA lesions included dysplasia (44%), RA hypoplasia (20%), midaortic syndrome (12%), RA aneurysm (12%), dissection (8%), and arteritis (4%). All patients had severe hypertension (>95 th percentile systolic or diastolic pressure adjusted for gender, age, and height). RA repair comprised 25 bypasses (73%) consisting of 28% saphenous vein, 60% hypogastric artery, and 12% polytetrafluoroethylene; 2 patch angioplasties (6%), and 7 reimplantations (21%). Branch RA exposure was required in 28 kidneys (88%), and branch reconstruction was required in 61%. Warm in situ repair was used in 53%, in situ cold perfusion in 24%, and ex vivo cold perfusion in 23%. Of six bilateral RA repairs, one was staged and two patients are awaiting a staged repair. Combined aortic reconstruction was required in three patients. No unplanned nephrectomy was performed. There were no perioperative deaths. Hypertension was cured in 36%, improved in 56%, and failed in 8% at mean follow-up of 46.4 +/- 7.8 months. The mean calculated glomerular filtration rate increased from 82.0 mL/min/1.73 m 2 preoperatively to 98.2 mL/min/1.73 m 2 postoperatively. The postoperative patency of 30 RA reconstructions was evaluated by angiography, RDS scanning, or both. At mean follow-up of 32.8 months (median, 21.2 months), primary RA patency was 91%. No failures were observed after 2 months follow-up. Estimated survival was 100% at 60 months, with one death 9 years after surgery.

CONCLUSIONS

Renovascular hypertension in children and adolescents was caused by a heterogeneous group of lesions. All patients had RA repair, with arterial autografts in most of the RA bypasses. Cold perfusion preservation was used in half of the complex branch RA repairs. These strategies provided 91% primary patency at mean follow-up of 32.8 months, with beneficial blood pressure response in 92%. Surgical repair of clinically significant renovascular disease in children and adolescents is supported by these results.

Noninvasive imaging of the renal arteries

Currently, four screening/diagnostic studies are available that provide imaging of the renal arteries: duplex ultrasonography, CT angiography, MR angiography, and intravenous DSA. Intravenous DSA is no longer used because of better imaging with MR and CT angiography. MR angiography, CT angiography, and duplex ultrasonography provide excellent sensitivity and specificity when performed by experienced personnel. The screening test of choice depends on the availability, expertise, and cost at individual centers.

Renal artery stenosis: duplex US after angioplasty and stent placement

PURPOSE

To evaluate the hemodynamic outcome of technically successful percutaneous transluminal renal artery angioplasty and stent placement (PTRAS) with duplex ultrasonography (US).

MATERIALS AND METHODS

Eighteen patients who underwent PTRAS in 22 renal arteries were prospectively examined. All had abnormal preprocedural duplex US findings. Those who had significant renal artery stenosis (>70%) at angiography and underwent technically successful percutaneous interventions were enrolled. Standard intrarenal duplex US parameters (acceleration index [AI], acceleration time, waveform morphology grade, and resistive index) were compared before and after interventions.

RESULTS

A significant AI increase occurred after PTRAS (9.02 m/sec(2) +/- 4.85 [SD]), as compared with before intervention (2.34 m/sec(2) +/- 2.03; P <.001). Acceleration time significantly decreased from 0.084 second +/- 0.049 to 0.032 second +/- 0.008 (P <.01). There was also a significant resistive index increase from 0.69 +/- 0.12 to 0.79 +/- 0.12 (P <.01). Abnormal waveform morphology (modified Halpern waveform grade 3-6) was present in 19 (86%) of 22 intrarenal arteries prior to intervention, as compared with one (5%) after PTRAS (P <.001). In the instance in which an abnormal waveform persisted after intervention, waveform morphology improved from grade 6 to grade 3, with a concomitant AI increase from 0.96 to 5.1 m/sec(2).

CONCLUSION

The findings suggest an important potential role for duplex US in noninvasive assessment of the immediate hemodynamic outcome and long-term follow-up of PTRAS.

Clinical evidence of contralateral renal parenchymal injury in patients with unilateral atherosclerotic renal artery stenosis

It has been postulated that the kidney contralateral to a significant renal artery stenosis may be at risk for accelerated arteriolar nephrosclerosis. Duplex ultrasound is capable of detecting and classifying renal artery stenosis and examining parenchymal flow. Renal flow patterns are a reflection of resistance, which increases with parenchymal pathology. One-hundred fifty-one patients with atherosclerotic renal artery stenosis (ARAS) were prospectively studied with duplex ultrasonography. Renal arteries were classified as normal, <60% stenosis, > or =60% stenosis, or occluded. The renal artery end-diastolic ratio (EDR) (end-diastolic velocity/peak systolic velocity) was measured. EDR decreases as resistance to flow increases. There were 81 patients with a unilateral > or =60% ARAS. The EDR was significantly lower in the kidney contralateral to the > or =60% ARAS (0.27 +/- 0.08 versus 0.30 +/- 0.08; p = 0.001, paired t-test). The absolute difference in EDR was even more pronounced in the subgroup of 15 diabetic patients with a > or =60% ARAS (0.22 +/- 0.08 versus 0.27 +/- 0.08; p = 0.004). This study offers clinical evidence that a unilateral hemodynamically significant ARAS is associated with the development of arteriolar nephrosclerosis in the contralateral kidney. These results have important implications on blood pressure control, renal function, and response to renal revascularization in this patient population.

Results of percutaneous transluminal angioplasty for atherosclerotic renal artery stenosis: a follow-up study with duplex ultrasonography

PURPOSE

The short and long-term anatomic results of percutaneous transluminal renal angioplasty (PTRA) in the treatment of atherosclerotic renovascular disease have been poorly documented because of a lack of follow-up arteriography. The purpose of this study was to evaluate the anatomic results of PTRA with serial duplex examinations.

METHODS

The records of 41 patients who underwent 52 primary PTRA procedures and had subsequent duplex follow-up of at least 6 months were reviewed. After PTRA, renal arteries were classified as normal, < 60% stenosis, > or = 60% stenosis, or occluded on the basis of previously validated duplex criteria.

RESULTS

The study group included 26 men and 15 women with a mean age of 65 years, who were observed for a mean interval of 34 months. Endovascular stents were placed in 12 of the 52 arteries. The initial post-PTRA renal artery stenosis classification (based on arteriography or duplex scan) was normal in 23, < 60% in 19, and > or = 60% in 10. The cumulative incidence of restenosis from normal to > or = 60% was 13% at 1 year and 19% at 2 years. The cumulative incidence of restenosis from < 60% to > or = 60% was 44% at 1 year and 55% at 2 years. The cumulative incidence of progression from > or = 60% to occlusion was 10% at 2 years. Although 83% of the 12 stented arteries and only 33% of the 40 nonstented arteries were normal immediately after PTRA, after 1 year the stented renal arteries showed a 44% restenosis rate, whereas the nonstented renal arteries showed a 18% restenosis rate (p = 0.087).

CONCLUSIONS

Restenosis after PTRA for atherosclerotic disease is relatively common and correlates with the initial anatomic result. Although PTRA with stent placement yields superior immediate technical results, the high early restenosis rate is disturbing.

Renal artery fibromuscular dysplasia: results of current surgical therapy

PURPOSE

This retrospective review describes current surgical management of renal artery (RA) fibromuscular dysplasia (FMD) to define contemporary clinical characteristics and surgical results in patients over the age of 21 years.

METHODS

From January 1987 through March 1994, 40 consecutive adults with hypertension had operative RA repair of FMD at our center and form the basis of this report. From histologic and angiographic appearance, FMD was classified with regard to specific type, noting the presence of RA dissections, RA macroaneurysms and branch RA involvement. Associations between blood pressure response to operation and patient age, duration of hypertension, presence of extrarenal atherosclerosis, presence of branch renal artery disease, and primary or secondary procedure were examined. Clinical characteristics and blood pressure response in these contemporary patients were compared with the results reported from an earlier surgical series.

RESULTS

Unilateral RA repair was performed in 34 patients, and bilateral procedures were required in six patients. Branch renal artery repair was performed in 28 instances, including ex vivo RA repair in 11 patients. There were no perioperative or follow-up deaths; however, three RA grafts (7%) failed within 30 days of operation. Initial blood pressure response was considered cured in 33%, improved in 57%, and failed in 10%. Analysis demonstrated that patients older than 45 years of age had a significantly decreased rate of hypertension cure compared with younger patients; among patients younger than 45 years of age, duration of hypertension was inversely related to cure. Compared with earlier surgical series, our current group of patients was significantly older, with more frequent branch renal artery involvement and extrarenal atherosclerosis, and demonstrated decreased rate of hypertension cure.

CONCLUSION

A beneficial blood pressure response is currently observed in most selected patients after surgical correction of RA-FMD. Compared with earlier series, however, the present day patient differs in many respects, including a significantly decreased chance for hypertension cure after surgical repair.

Safety and efficacy of transaortic renal endarterectomy as an adjunct to aortic surgery

PURPOSE

A study was undertaken to assess the safety and efficacy of transaortic endarterectomy for orificial atherosclerotic renovascular disease (ASRD), particularly in conjunction with surgery for concomitant aortic disease.

METHODS

Forty-three consecutive patients with ASRD treated with transaortic orificial eversion endarterectomy were studied retrospectively to identify surgical indications, technical features, operative morbidity and mortality rates, and efficacy.

RESULTS

A total of 76 renal arteries underwent transaortic endarterectomy for hypertension (88% of patients) or serum creatinine of 1.5 mg/dl or greater (65% of patients), including two patients undergoing dialysis. Concomitant aortic surgery was performed in 39 patients for aneurysmal (n = 30) or occlusive (n = 9) disease. Two (2.6%) of 76 renal endarterectomies required intraoperative conversion to bypass because of poor flow, and three arteries (3.9%) were reimplanted or bypassed because of fragility of the renal orifice after endarterectomy. Thirty-day operative death occurred in two patients (4.7%), and major morbidity occurred in six (14.0%). Hypertension was cured or improved in 83% of patients with hypertension. Among patients with preoperative renal insufficiency, function was improved in 19%, with dialysis discontinued in one of two patients receiving dialysis, and function was worse in 23%, with one patient dependent on dialysis.

CONCLUSION

Transaortic renal endarterectomy is an acceptably safe and effective adjunctive technique in selected patients with combined aortic disease and ASRD.