Renal artery stenosis treated with stent deployment: indications, technique, and outcome for 108 patients

The Society for Vascular Surgery practice guidelines on follow-up after vascular surgery arterial procedures

Although follow-up after open surgical and endovascular procedures is generally regarded as an important part of the care provided by vascular surgeons, there are no detailed or comprehensive guidelines that specify the optimal approaches with regard to testing methods, indications for reintervention, and follow-up intervals. To provide guidance to the vascular surgeon, the Clinical Practice Council of the Society for Vascular Surgery appointed an expert panel and a methodologist to review the current clinical evidence and to develop recommendations for follow-up after vascular surgery procedures. For those procedures for which high-quality evidence was not available, recommendations were based on observational studies, committee consensus, and indirect evidence. Recognizing that there are numerous published reports on the role of duplex ultrasound for surveillance of infrainguinal vein bypass grafts, the Society commissioned a systematic review and meta-analysis on this topic. The panel classified the strength of each recommendation and the corresponding quality of evidence on the basis of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system: recommendations were graded either strong or weak, and the quality of evidence was graded high, moderate, or low. The resulting recommendations represent a wide variety of open surgical and endovascular procedures involving the extracranial carotid artery, thoracic and abdominal aorta, mesenteric and renal arteries, and lower extremity arterial revascularization. The panel also identified many areas in which there was a lack of high-quality evidence to support their recommendations. This suggests that there are opportunities for further clinical research on testing methods, threshold criteria, and the role of surveillance as well as on the modes of failure and indications for reintervention after vascular surgery procedures.

Resultados a longo prazo da angioplastia de artérias renais com stent na doença aterosclerótica: revisão sistemática

Resumo A doença renovascular aterosclerótica é a principal causa de hipertensão secundária. A história natural da doença demonstra taxas de progressão de 4 a 12% ao ano. Entre os métodos de tratamento existe a angioplastia com stent de artérias renais; porém, poucos estudos clínicos demonstraram seus resultados a longo prazo. Esta revisão sistemática da literatura se propõe a apresentar os resultados a longo prazo (acima de 24 meses) da angioplastia com stent de artérias renais na doença aterosclerótica em relação à função renal e aos níveis pressóricos no controle da hipertensão. Foi realizada uma ampla pesquisa, utilizando os termos apropriados, nas bases de dados LILACS, EMBASE, SCIELO, Cochrane Library e MEDLINE. De um total de 2.170 referências, apenas sete artigos contemplavam todos os critérios de inclusão. Conclui-se que, a longo prazo, há uma estabilização da função renal, redução dos níveis pressóricos e diminuição do número de classes de medicamentos anti-hipertensivos.

Renal artery stenosis: prevalence of, risk factors for, and management of in-stent stenosis

Atherosclerotic renal artery stenosis is common and is associated with hypertension and chronic kidney disease. More frequent use of percutaneous renal artery stent placement for the treatment of renal artery stenosis during the past 2 decades has increased the number of patients with implanted stents. In-stent stenosis is a serious problem, occurring more frequently than earlier reports suggest and potentially resulting in late complications. Currently, there are no guidelines covering the approach to restenosis after renal artery stent placement. This article reviews data on the prevalence of and risk factors for the development of in-stent stenosis and the clinical manifestations, evaluation, and treatment of in-stent stenosis and suggests a strategy for the management of patients after percutaneous renal artery stent placement.

Atherosclerotic renal artery stenosis and renal artery stenting: an evolving therapeutic option

Atherosclerotic renal artery stenosis is a common clinical problem for which the optimal therapeutic strategy remains to be defined. However, renal artery stenting procedures have significantly increased as one approach to treat this clinical problem. Despite improvements in device design and technical performance of the procedure, the benefits and results of randomized clinical trials of renal artery stenting as a therapy remain confusing. Understanding the epidemiology, pathophysiology and natural history of renal artery stenosis are central to improving the outcomes of renal artery stenting. Developing both noninvasive and invasive predictive tools to better identify which patient will respond to renal revascularization will also be beneficial. In this article, we will present an overview of atherosclerotic renal artery disease. The results of renal artery stenting will be discussed and from this, the available noninvasive and invasive tools available to assess the clinical and hemodynamic significance of renal artery stenosis will be presented.

Endovascular treatment of peripheral vascular disease

Peripheral arterial disease (PAD) affects about 27 million people in North America and Europe, accounting for up to 413,000 hospitalizations per year with 88,000 hospitalizations involving the lower extremities and 28,000 involving embolectomy or thrombectomy of lower limb arteries. Many patients are asymptomatic and, among symptomatic patients, atypical symptoms are more common than classic claudication. Peripheral arterial disease also correlates strongly with risk of major cardiovascular events, and patients with PAD have a high prevalence of coexistent coronary and cerebrovascular disease. Because the prevalence of PAD increases progressively with age, PAD is a growing clinical problem due to the increasingly aged population in the United States and other developed countries. Until recently, vascular surgical procedures were the only alternative to medical therapy in such patients. Today, endovascular practice, percutaneous transluminal angioplasty with or without stenting, is used far more frequently for all types of lower extremity occlusive lesions, reflecting the continuing advances in imaging techniques, angioplasty equipment, and endovascular expertise. The role of endovascular intervention in the treatment of limb-threatening ischemia is also expanding, and its promise of limb salvage and symptom relief with reduced morbidity and mortality makes percutaneous transluminal angioplasty/stenting an attractive alternative to surgery and, as most endovascular interventions are performed on an outpatient basis, hospital costs are cut considerably. In this monograph we discuss current endovascular intervention for treatment of occlusive PAD, aneurysmal arterial disease, and venous occlusive disease.

Cost-effectiveness analysis of treatment of renal-artery stenoses by medication, angioplasty, stenting and surgery

This study analysed the cost-effectiveness of four different treatment modalities (medical therapy, PTA with and without stent, and surgery) for the therapy of renal-artery stenoses in hypertensive patients in Germany. A computerised, predictive decision-analytic model, based on economic input data and the cost of medical care in Germany, and the results of published data from prospective clinical trials, was developed. The economic analysis was performed from the perspective of a third-party payer. The base-case analysis showed that the primary end-point (major vascular bleeding, stroke, dialysis, or repeat arterial revascularisation) was reached at 36 months by 82.4% of the patients in the medical treatment group, 81.4% in the angioplasty group, 52.9% in the surgical group and 27.7% in the stent group. The average reimbursed treatment cost per patient after 3 years was € 9121 (medication), € 17 164 (surgery), € 14 670 (PTA), and € 8437 (stent). This resulted in a cost-effectiveness ratio of € 51 752 (medical treatment), € 36 454 (surgery), € 78 766 (PTA), and € 11 663 (stent) per event-free patient at 3 years. The accelerated cost-development after balloon dilatation was caused by higher rates of restenosis compared with primary stent implantation. The analysis of published prospective clinical data and current economic variables for renovascular interventions leads to the conclusion that a strategy using primary stent implantation is more cost-effective than stand-alone balloon dilatation. Both medical therapy and surgery offer a better cost-effectiveness ratio than PTA treatment alone.

Proteinuria as a predictor of renal functional outcome after revascularization in atherosclerotic renovascular disease (ARVD)

BACKGROUND

Renal revascularization is performed in 16% of newly diagnosed patients with atherosclerotic renovascular disease (ARVD). Although there may be some improvement in hypertension control as a result of intervention, renal functional outcomes are known to vary. Pre-existing renal parenchymal injury, as manifested by proteinuria, is associated with poor functional outcome in conservatively managed ARVD patients, but this association has not been investigated in patients undergoing revascularization.

METHODS

Retrospective case note review of 83 ARVD patients who underwent renal revascularization in four centres within a renal network between 1998 and 2003 was undertaken. Amongst other parameters, baseline proteinuria was correlated with renal functional outcome post revascularization. Renal functional outcome was determined over a mean follow up of 22 months by rate of change of estimated glomerular filtration rate (eGFR) over time.

RESULTS

Univariate analysis showed that proteinuria >0.6 g/day was the only significant predictor of poor outcome after revascularization. The relationship persisted with multivariate analysis, and linear regression showed a correlation between baseline proteinuria and decline in eGFR with time (r(2) = 0.058, P = 0.039).

CONCLUSION

This study confirms that prior renal parenchymal injury, here reflected by proteinuria at baseline, is a major arbiter of renal functional outcome after renal revascularization in ARVD.

Renal artery revascularization: collaborative approaches for specialists

Endovascular revascularization for atherosclerotic renal artery stenosis (RAS) is the revascularization strategy of choice for patients with hemodynamically and clinically significant renal artery stenosis. Surgical revascularization is reserved for failed endovascular therapy or concomitant abdominal aortic surgery. Endovascular renal artery stenting is associated with excellent technical success, low complication rates, and acceptable long-term patency. This technique has been proven to be beneficial for preserving kidney function and stabilizing or improving blood pressure control in selected patients. Nevertheless, deterioration in kidney function after the procedure in 10% to 20% of cases may limit the immediate benefits of this technique. Atheroembolism appears to play an important role in the cause of kidney dysfunction after renal revascularization. Renal revascularization with a distal embolic protection device is a promising strategy in reducing the risk of atheroembolism and deterioration in kidney function.

Durability of renal artery stents in patients with transrenal abdominal aortic endografts

OBJECTIVE

The management of renal artery stenosis in patients with abdominal aortic aneurysms continues to be complex and technically challenging despite advances in endovascular therapy. There is growing concern about the durability of renal artery stents in the setting of transrenal abdominal aortic endografts. This study reports a single-center experience of renal artery stenting with transrenal abdominal aortic endografts for patients with renal artery stenosis.

METHODS

All patients undergoing endovascular abdominal aortic aneurysm repair preceded or followed by renal artery stent placement between January 1999 and December 2005 were retrospectively reviewed from a prospectively gathered endovascular database. Patients were surveyed after renal stent procedures with multidetector computed tomography angiography or duplex sonography. The surveillance data were analyzed for primary patency of the renal artery stent at 6 months, incidence of complications, need for secondary interventions, and changes in creatinine clearance (CrCl).

RESULTS

Sixty-two renal artery stents were placed in 56 patients (44 men, 12 women) with a mean age of 77.3 years (range, 61 to 94 years). Forty-one were placed before the endograft procedure, eight were placed during the endograft procedure, and 13 were placed postoperatively. There were no major or minor complications related to the renal artery stent procedures. Transrenal aortic endografts were used in 44 of the 56 patients, and 12 had devices with infrarenal fixation. The mean follow-up was 18.5 months (range, 1 to 73 months). The 6-month primary patency, which could be evaluated for 51 renal artery stents, was 97.4% (37/38) in patients with transrenal fixation and 84.6% (11/13) in patients with infrarenal fixation. The overall rate of in-stent restenosis was 8.5% (4/47) in the transrenal fixation group and 20.0% (3/15) in the infrarenal fixation group. The overall occlusion rate was 2.1% (1/47) in the transrenal fixation group and 0% (0/15) in infrarenal fixation group. Five (83.3%) of six patients underwent successful treatment of in-stent restenosis with placement of a new stent in all five cases. CrCl decreased in the total group by 4.2 +/- 11.8 mL/min, by 4.7 +/- 12.0 mL/min in patients with transrenal fixation, and by 2.2 +/- 11.0 mL/min in patients with infrarenal fixation.

CONCLUSION

The presence of a transrenal aortic endograft did not affect the outcome of the renal artery revascularization procedure in this cohort. Renal artery stenting in the presence of transrenal abdominal aortic endografts appears to be a safe procedure without adverse effect on renal artery stent patency or renal function.

Endovascular Treatment of Peripheral Vascular Disease

An estimated 10 million people in the U.S. have symptomatic peripheral arterial disease (PAD); 20 to 30 million have asymptomatic PAD. The prevalence of intermittent claudication increases with age, affecting >5% of patients over 70. The incidence of claudication doubles or triples in patients with diabetes. As people grow older, symptoms from peripheral vascular disease increasingly limit daily activity. Until recently, vascular surgical procedures were the only alternative to medical therapy in such patients. Today, advances in minimally invasive percutaneous interventions have made endovascular procedures the primary modality for revascularization in most patients. Compared with open surgical procedures, endovascular interventions offer comparable or superior long-term rates of success with very low rates for morbidity and mortality. Furthermore, most of these interventions are performed on an outpatient basis, reducing hospital stays considerably. In this monograph we discuss current endovascular interventions for treating occlusive PAD, aneurysmal arterial disease, and increasingly common venous occlusive diseases.

Renal angioplasty and stenting: long-term results and the potential role of protection devices

Renal angioplasty and stenting have become the first treatments to be proposed to patients presenting with renal artery stenosis. The immediate technical success rate is high, with a low complication rate and good long-term patency. In most reports, renal stenting has been proven to improve blood pressure. However, despite good immediate- and long-term results, postprocedural deterioration of renal function is a concern, and may occur after renal artery angioplasty and stenting in 20 to 40% of patients, which limits the immediate benefits of this technique. Of the causes of this deterioration in renal function, atheroembolism seems to play an important role. Contrary to earlier beliefs that atheroembolization is not an issue during percutaneous catheter interventions, there is now mounting evidence that distal atherosclerotic debris commonly embolizes from lesions in many vascular territories during percutaneous interventions. Atheroembolism seems to be the root cause of many procedural complications wherever atherosclerotic lesions are treated. Distal embolization was first demonstrated in saphenous vein grafts and now, clinical data are proving that similar embolization and distal-organ complications also occur during catheter treatment in certain native coronary lesions, carotid stenting and renal artery stenting, demonstrating the role and efficacy of protection devices to reduce the incidence of end-organ complications. The same protection devices (protection balloon and filters) utilized for coronary or carotid procedures may be used to protect the kidney from atheroembolism. In this review, the authors discuss recently published data concerning the techniques and results of renal angioplasty and stenting procedures performed under protection, and evaluate the benefits of this technique on renal function and its role in the future. Indications for this technique need to be discussed.

Atherosclerotic renovascular disease in United States patients aged 67 years or older: Risk factors, revascularization, and prognosis

BACKGROUND

Although atherosclerotic renovascular disease is increasingly recognized in chronic kidney disease, few national level studies have examined its clinical epidemiology.

METHODS

Claims data from a 5% random sample of the United States Medicare population were used to select patients without atherosclerotic renovascular disease in the 2 years preceding December 31, 1999 (N= 1,085,250), followed until December 31, 2001.

RESULTS

The incidence of atherosclerotic renovascular disease was 3.7 per 1000 patient-years. Major antecedent associations [P < 0.05, with adjusted hazards ratios (HR) > 1.5] included chronic kidney disease (adjusted HR 2.54), hypertension (2.42), peripheral vascular disease (2.00), and atherosclerotic heart disease (1.70). Adverse event rates after incident atherosclerotic renovascular disease greatly exceeded those in the general population (P < 0.0001): atherosclerotic heart disease, 303.9 per 1000 patient-years (vs. 73.5 in the general population); peripheral vascular disease, 258.6 (vs. 52.2); congestive heart failure, 194.5 (vs. 56.3); cerebrovascular accident or transient ischemic attack, 175.5 (vs. 52.9); death, 166.3 (vs. 63.3); and renal replacement therapy, 28.8 (vs. 1.3). Among atherosclerotic renovascular disease patients, 16.2% underwent a renal revascularization procedure, percutaneously in 96%. Revascularization was not associated with renal replacement therapy, congestive heart failure, or death but was associated with atherosclerotic heart disease (adjusted HR 1.42) (P= 0.004) and peripheral vascular disease (adjusted HR 1.38) (P= 0.002).

CONCLUSION

Atherosclerotic renovascular disease is strongly associated with cardiovascular disease, both past and future. Absolute cardiovascular risk exceeds that of renal replacement therapy. Renal revascularization is used selectively and shows inconsistent associations with cardiovascular outcomes, renal replacement therapy, and death.

Low-profile Stent Placement with the Monorail Technique for Treatment of Renal Artery Stenosis: Midterm Results of a Prospective Trial

PURPOSE

To determine feasibility, safety, and midterm patency of a monorail balloon stent device for the treatment of renal artery stenosis (RAS).

MATERIALS AND METHODS

During a period of 30 months, 47 patients (with severe hypertension, n=45; renal insufficiency, n=20) with 50 cases of RAS and indications for stent implantation (calcified ostial lesion, n=41; insufficient percutaneous transluminal angioplasty, n=6; dissection, n=3) were enrolled into the prospective evaluation. After predilation, 59 stents (Rx-Herculink 4 mm, n=2; 5 mm, n=19; 6 mm, n=35; 7 mm, n=3) were implanted under manometer control with use of the long-sheath technique (5 F; 6 F for 7-mm stents) via a femoral (n=44) or transbrachial approach (n=6). Parameters of hypertension and renal insufficiency were determined before and after the procedure and for a maximum of 18 months. Restenosis rate was determined with color duplex ultrasonography.

RESULTS

Renal artery stent placement (mean diameter, 5.7 mm; mean length, 16 mm) was technically successful in all cases (100%). Mean blood pressure and serum creatinine level decreased from 177/93 mm Hg to 145/78 mm Hg and from 1.8 mg/dL to 1.5 mg/dL, respectively. Within 48 hours after the implantation, acute occlusions occurred in two patients, supposedly triggered by cholesterol embolization. Primary and primary assisted patency rates were 87% and 92% at 6 months and 75% and 84% at 18 months.

CONCLUSIONS

Renal artery stent placement with the rapid-exchange monorail system is a safe procedure with promising patency rates. In combination with the long-sheath technique, adequate control of stent deployment is guaranteed during the entire intervention. The low profile of the device facilitates the use of small sheaths (5 F) to minimize access-site complications.

A Review of the Current Treatment of Renal Artery Stenosis

PURPOSE

Atherosclerotic renal artery stenosis (ARAS) is associated with morbidity and mortality consequent to progressive ischemic renal failure and the cardiovascular consequences of hypertension. There is considerable uncertainty concerning the optimal management of patients with this condition. This review considers the aetiological factors and the physiologic consequences of ARAS and compares the results of clinical studies of medical and endovascular therapies on blood pressure control and preservation of renal function.

RESULTS

Although, in patients with fibromuscular disease the results of percutaneous transluminal angioplasty (PTA) are clearly superior to medical therapy and surgery, in asymptomatic patients with ARAS the antihypertensive benefits and preservation of renal function of endovascular, surgical and medical therapies appear similar. In selected symptomatic patients interventions may, however, be life-saving. Surgery is generally reserved for arterial occlusions with preserved renal parenchyma and function.

CONCLUSIONS

The results of larger, multicentre, randomised, controlled trials are required to clearly clarify the role of interventional therapy in asymptomatic patients.

Delicate Percutaneous Renal Artery Stenting Minimizes Postoperative Renal Injury and Protects Kidney in Patients With Severe Atherosclerotic Renal Artery Stenosis and Impaired Renal Function

Percutaneous transluminal renal artery stenting (PTRAS) is associated with declining renal function in a non-negligible portion of patients and is inflicted by different mechanisms, including atheroembolism. This study investigated whether delicate PTRAS to reduce atheroembolism might minimize postoperative renal injury and better preserve renal function. Patients undergoing PTRAS performed by experienced interventional cardiologists, applying coronary intervention concepts, techniques, devices and delicacy principles whenever possible, were prospectively studied. A total of 34 patients (29 M/5 F) with impaired renal function (group A, creatinine 2.4 +/- 0.1 mg/dL) and another 20 patients (16 M/4 F) with normal serum creatinine (group B, baseline creatinine 1.2 +/- 0.0 mg/dL) were studied. PTRAS was successfully performed in all but one group A patient. During a 6-month follow-up, systolic and diastolic blood pressure (130 +/- 2 versus 148 +/- 4 mmHg, P = 0.001 and 70 +/- 2 versus 78 +/- 3 mmHg, P = 0.006) and serum creatinine (2.1 +/- 0.1 versus 2.4 +/- 0.1 mg/dL, P < 0.001) were all significantly lowered in group A patients. Using a 20% change cut-off value, renal function improved in eight (24%), remained unchanged in 24 patients (73%), and deteriorated in only one patient (3%). The corresponding alterations in blood pressure and renal function were insignificant in group B patients. Patients with bilateral involvement (eleven patients) also had significantly lowered serum creatinine on follow-up. In conclusion, delicately practiced PTRAS can reduce the rate of postprocedural renal deterioration in patients with impaired renal function, and should be adopted in every renal intervention.

Sonographic follow-up after visceral artery stenting

OBJECTIVE

The aim of this study was to evaluate the sonographic features of stents and the flow parameters of the visceral arteries after stent implantation.

METHODS

Since 1996, 34 stenoses of the visceral arteries (2 mesenteric, 4 celiac trunk, and 28 renal arteries) in 28 patients have been treated with metallic stent implantation in the Department of Radiology of Szeged Medical University. All these patients were regularly followed sonographically. For the diagnosis of restenosis, previously published criteria were used.

RESULTS

All the mesenteric and celiac stents could be visualized, but none of the renal stents were clearly seen sonographically. The flow parameters could be established in all cases. Sonographic examination revealed 1 occlusion, 2 restenoses, and 1 stent displacement. All these abnormalities were confirmed by other imaging modalities.

CONCLUSIONS

Sonography is a useful tool in the follow-up of patients after visceral artery stenting. Despite the fact that none of the renal artery stents were visualized directly, the flow parameters could be evaluated, and the pathologic changes were found.

Value, limitations, and techniques of renal artery stenting

Percutaneous therapy for renovascular occlusive disease has become the preferred alternative to open renal artery revascularization. Angioplasty and stenting of renal artery stenoses has been shown to be a safe and effective option for severe hypertension and ischemic nephropathy. Catheter-based treatment, especially when performed with lower-profile systems can be performed with minimal morbidity and a reliably high degree of initial technical success. The long-term beneficial effects on blood pressure control and renal function, while debated, appear to be valid. In this article, data supporting the value and limitations of renal artery stenting are reviewed, and our technique for renal artery stenting using a lower-profile platform of balloons and stents is described.

Current issues in the diagnosis and management of patients with renal artery stenosis: a cardiologic perspective

Renal artery stenosis most often is caused by atherosclerosis. Although patients with renal artery stenosis can be managed conservatively, renal revascularization may be indicated, particularly in patients with refractory hypertension on a multidrug regimen and patients with declining renal function. Duplex ultrasonography of the renal arteries and magnetic resonance angiography are currently the most efficient noninvasive methods for the evaluation of renal artery stenosis. Selective digital subtraction renal arteriography remains the gold standard for the definitive diagnosis. In selected patients undergoing coronary studies and angiography immediately after the coronary procedure can be efficient. Atherosclerotic renal artery lesions, which commonly affect the renal artery ostium, can be treated safely and effectively with balloon-expandable stents. Successful angioplasty commonly results in improved control of hypertension, but an overall benefit on renal function and/or patient survival has not been shown. Generally the risk/benefit ratio of renal artery stenting seems favorable, but further randomized studies are needed for evidence-based decision making. All patients with atherosclerotic renal artery stenosis should receive rigorous secondary prevention measures including platelet inhibitors, statins, and beta-blockers.

Renal angioplasty and stenting under protection: The way for the future?

The purpose of this study was to evaluate the feasibility and safety of renal artery angioplasty and stenting utilizing a distal protection device to reduce the risk of intraprocedural artery embolism and avoid deterioration of the renal function. Fifty-six hypertensive patients (32 men; mean age, 66 +/- 11.8 years; range, 22-87) with atherosclerotic renal artery stenosis (8 bilateral) underwent angioplasty and stenting with distal protection in 65 renal arteries (58 ostial lesions). Five patients had a solitary kidney, 18 a renal insufficiency. The lesion was crossed either with a GuardWire temporary occlusion balloon (n = 38), which was inflated to provide parenchyma protection or with a filter (EPI Filter; n = 26), or with Angioguard (n = 1), which allows a continuous flow. Generated debris was aspirated and analyzed. Blood pressure and serum creatinine levels were followed. Immediate technical success was 100%. All lesions except one were stented, either directly (43 ostial lesions) or after predilatation (22 ostial lesions). Visible debris were aspirated with the PercuSurge in all patients or removed with filters in 80% of the patients. Mean particle number and diameter were 98.1 +/- 60.0 per procedure (range, 13-208) and 201.0 +/- 76.0 microm (range, 38-6,206), respectively. Mean renal artery occlusion time was 6.55 +/- 2.46 min (range, 2.29-13.21) with the PercuSurge device. Mean time in situ (filters) was 4.25 +/- 1.12 min. Mean follow-up was 22.6 +/- 17.6 months (range, 1-47). Systolic and diastolic blood pressure declined from 169.0 +/- 15.2 and 104.0 +/- 13.0 mm Hg, respectively, to 149.7 +/- 12.4 and 92.7 +/- 6.7 mm Hg after the procedure. The mean creatinine level remains constant during the follow-up. At 6-month follow-up (45 patients), renal function did not deteriorate in any patient, whereas 8 patients with baseline renal insufficiency improved after the procedure. At 3 years (19 patients), renal function deteriorated only in 1 patient with renal insufficiency and in 1 patient treated for bilateral renal stenosis, one side without protection. These preliminary results suggest the feasibility and safety of distal protection during renal interventions to protect against atheroembolism and to avoid renal function deterioration. This technique's beneficial effects should be evaluated by randomized studies.

Guidelines for the Reporting of Renal Artery Revascularization in Clinical Trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Use of external iliac artery in renal revascularization surgery: long-term angiographic assessment

PURPOSE

The external iliac artery has physical characteristics, in particular, caliber and length, similar to those of the renal artery and would thus seem to be an ideal substitute for it. However, there are no studies in the literature designed to confirm this possibility. The present study was designed to demonstrate the feasibility of use of the external iliac artery as a substitute for the renal artery in surgical revascularization of renal artery fibrodysplasia and to assess the long-term biologic behavior of the external iliac artery so used.

METHODS

Twelve patients (11 female, 1 male), ages 1 to 43 years (mean, 24.4 years), with severe hypertension underwent aortorenal bypass grafting with use of the external iliac artery to treat preocclusive stenotic lesions (n = 7), complete occlusion (n = 3), or aneurysm (n = 2) of the renal artery. It was considered unnecessary to reestablish circulation in the donor limb in 2 patients (young children), and transposition of the ipsilateral internal iliac artery was performed in 9 patients; in the remaining patient circulation was reestablished with insertion of an iliofemoral prosthesis.

RESULTS

There were no operative deaths. In 1 patient nephrectomy was necessary because of occlusion of the graft as a consequence of technical complications. In 8 patients there was immediate normalization of blood pressure without aid of medication, and in the remaining 3 patients an antihypertensive drug was prescribed. Two patients were lost to follow-up; the other 9 were assessed with angiography at a mean of 8.8 years after the operation. All grafts were found to be in excellent condition, with no evidence of dilatation, kinking, twisting, anastomotic fibroplasia, or wall irregularities.

CONCLUSION

On the basis of this experience, the external iliac artery is confirmed as a substitute for the renal artery, and the excellent long-term results would seem to make it particularly useful in young patients with long life expectancy, such as those with renal artery fibrodysplasia.

Prevalence and predictors of renal artery stenosis in Chinese patients with coronary artery disease

BACKGROUND

Ischaemic nephropathy is currently a major public health issue in atherosclerotic populations. Although atherosclerotic cardiovascular disease in Asia has reached epidemic proportions over the last two decades, there is little published data on the prevalence of atherosclerotic renal artery stenosis (ARAS) in Oriental subjects. Because ARAS may be clinically silent until end-stage renal failure sets in, it is important to identify patients with significant but clinically unsuspected ARAS. ARAS and coronary artery disease (CAD) often coexist.

AIMS

The purpose of the present study was to evaluate the prevalence and predictors of ARAS among Chinese patients with CAD.

METHODS

A total of 230 consecutive Chinese patients with CAD confirmed by coronary angiography underwent an abdominal aortogram in the same sitting to screen for ARAS. Patient demographics and comorbidities were analysed for any association with ARAS.

RESULTS

A total of 34 (14.8%) patients was found to have significant ARAS. Age and multivessel CAD were independent predictors of ARAS. Hypertension, renal insufficiency, extracranial cerebrovascular disease and female gender were also associated with a higher risk of ARAS but did not independently predict ARAS.

CONCLUSION

Clinically silent yet angiographically significant ARAS is common among CAD patients. The prevalence and predictors of ARAS among Chinese patients with CAD are similar to those reported for Caucasian subjects. Underlying ARAS should be suspected in CAD patients with such comorbidities as hypertension, renal insufficiency, extracranial cerebrovascular disease, and more so in the elderly and those with multivessel disease.

Atherosclerotic ischemic renal vascular disease: do published outcomes justify the overzealous diagnostic approaches?

Atherosclerotic renal vascular disease is being recognized more frequently in an elderly patient population with chronic kidney disease. It also is much easier to diagnose and treat, at this time, because of the wide availability of coronary angiography and other radiologic imaging studies. In general, patients with atherosclerotic ischemic renal vascular disease are much sicker than the usual ESRD patient with more cardiac comorbidity and higher mortality rates. It is important to determine whether the lesions in the renal artery are physiologically significant before performing an intervention. The interventions are often risky with significant morbidity. Nephrologists should guide their colleagues to follow prudent courses of action. There are no evidence-based guidelines in this area.

Atherosclerotic Renal Artery Stenosis

The clinical diagnosis of renal artery stenosis relies on a high index of suspicion and confirmation by noninvasive imaging modalities. There are three distinct clinical syndromes associated with renal artery stenosis: renin-dependent hypertension, essential hypertension, and ischemic nephropathy. Clinical features that should heighten suspicion for renal artery stenosis include abrupt-onset or accelerated hypertension at any age, unexplained acute or chronic azotemia, azotemia induced by angiotensin-converting enzyme (ACE) inhibitors, asymmetric renal dimensions, and congestive heart failure with normal ventricular function. Patients with true renin-dependent (renovascular) hypertension are typically young or middle-age women with renal fibromuscular dysplasia (FMD). Initial therapy for renovascular hypertension associated with FMD is an ACE inhibitor; refractory hypertension responds readily to balloon angioplasty without stenting. Elderly patients with generalized atherosclerosis and hypertension often have atherosclerotic renal artery stenosis (ARAS); hypertension in these patients is usually not renin dependent (ie, essential hypertension). Hypertension alone, even if treated with multiple medications, is not a compelling indication for renal artery revascularization; these patients should be treated aggressively with antihypertensive medical therapy. Renal artery revascularization with stenting may be considered for refractory severe hypertension, and would be expected to improve blood control and modestly reduce medication requirements. Renal revascularization rarely cures hypertension in patients with ARAS. Patients with ARAS, hypertension, and end-organ injury should be considered for renal revascularization. Manifestations of end-organ injury include nonischemic pulmonary edema; hypertensive crisis associated with acute coronary syndrome, aortic dissection, or neurologic impairment; and renal insufficiency. Ischemic nephropathy is best treated before the development of advanced renal failure. The best candidates for revascularization are those with baseline serum creatinine less than 2.0 mg/dL, bilateral renal artery stenosis, normal renal resistive indices, no proteinuria, and one or more manifestations of end-organ injury. In these patients, renal revascularization is best accomplished by stenting, although surgical revascularization may be considered in patients with concomitant severe aortic aneurysmal or occlusive disease.

Renal artery stent placement: complications at a single tertiary care center

PURPOSE

To describe complications after renal artery stent placement in patients with atherosclerotic renal artery stenosis (RAS) at a single tertiary care center and analyze the risk factors for these complications.

MATERIALS AND METHODS

Medical records and angiograms of 171 patients who underwent a total of 179 consecutive percutaneous transluminal renal artery stent placement (PTRS) procedures for atherosclerotic RAS were retrospectively reviewed. Data on patient comorbidities, procedure indication, lesion location, serum creatinine level, and procedure-related complications were analyzed. The Wilcoxon rank-sum test was used to assess the association of continuous risk factors with complications, and the chi(2) test was used to assess the association of categoric risk factors with outcomes.

RESULTS

The technical success rate for PTRS was 98%. Major complications included renal infarction in five patients (2.8%), permanently increased serum creatinine level in 10 patients (5.6%) that required hemodialysis in five (2.8%), blood transfusion in four patients (2.2%), surgical intervention for procedure-related complications in two patients (1.1%), and deep vein thrombosis in one patient (0.6%). Overall, major complications occurred in 15 procedures (8.4%). Death within 30 days after PTRS occurred in two patients (1.1%), but neither death was definitively caused by the procedure. No risk factors were found to be significantly (P <.05) associated with major complications. Patients with renal artery site or renal function complications tended to be older (P =.01) and have higher creatinine levels (P =.06).

CONCLUSIONS

Renal artery stent placement allows treatment of advanced atheromatous RAS in patients with significant medical and surgical comorbidities. Complications are frequent but few have long-term significance.

Volume-rendered multidetector CT angiography: noninvasive follow-up of patients treated with renal artery stents

OBJECTIVE

The purpose of our study was to evaluate the role of multidetector CT (MDCT) angiography with volume rendering for estimating the patency of renal artery stents.

SUBJECTS AND METHODS

In 16 patients, 16 renal artery stents were evaluated with MDCT renal angiography and digital subtraction angiography (DSA). CT data were evaluated using multiplanar volume reformations and the volume-rendering algorithm with three different volume-rendered parameter settings (low-to-high, high-to-low, and high-low-high opacity transfer functions: VR(LH), VR(HL), and VR(VE), respectively). Targeted images of each stent were rendered in paraaxial and paracoronal planes and were interactively interpreted. The overall restenosis severity was measured on postprocessed paraaxial and paracoronal images and compared with that obtained on DSA using linear regression analysis. Image quality and lumen delineation on rendered images were also compared using Wilcoxon's signed rank test.

RESULTS

Eight restenoses were identified on DSA. Correlations between restenosis severity measured with DSA and those measured with MDCT were significant (p < 0.001). Volume rendering with VR(HL) allowed the best correlation with DSA (reviewer 1, r(2) = 0.86; reviewer 2, r(2) = 0.94) and was significantly better than multiplanar volume reformations (p = 0.028). Overall image quality was high with all rendering techniques and with no significant differences (p > 0.59, for all comparisons). Stent lumen was well delineated with volume-rendering modalities; however, VR(HL) was significantly better than VR(LH) (p = 0.033).

CONCLUSION

Volume-rendered MDCT angiography enabled high-quality three-dimensional reproducible evaluation of the patency of implanted renal artery stents. Volume rendering with VR(HL) achieved the best performance.

Guidelines for the reporting of renal artery revascularization in clinical trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Magnetic resonance angiography for the diagnosis of renal artery stenosis: a meta-analysis

AIM

To review the published literature comparing the diagnostic accuracy of magnetic resonance angiography (MRA) with and without gadolinium in diagnosing renal artery stenosis, using catheter angiography as reference.

MATERIALS AND METHODS

A meta-analysis was performed of English language articles identified by computer search using PubMed/MEDLINE, followed by extensive bibliography review from 1985 to May 2001. Inclusion criteria were: (1) blinded comparison with catheter angiography; (2)indication for MRA stated; (3) clear descriptions of imaging techniques; and (4) interval between MRA and catheter angiography < 3 months and only the largest of all studies from one centre was selected in the analysis.

RESULTS

A total of 39 studies were identified, of which 25 met the inclusion criteria. The number of patients included in the meta-analysis was 998: 499 with non-enhanced MRA and 499 with gadolinium-enhanced MRA. The sensitivity and specificity of non-enhanced MRA were 94% (95% CI: 90-97%) and 85% (95% CI: 82-87%), respectively. For gadolinium-enhanced MRA sensitivity was 97% (95% CI: 93-98%) and specificity was 93% (95% CI: 91-95%). Thus, specificity and positive predictive value were significantly better for gadolinium-enhanced MRA (P < 0.001). Accessory renal arteries were depicted better by gadolinium-enhanced MRA (82%; 95% CI: 75-87%) than non-gadolinium MRA (49%; 95% CI: 42-60%) (P < 0.001).

CONCLUSIONS

Gadolinium-enhanced MRA may replace arteriography in most patients with suspected renal artery stenosis, and has major advantages in that it is non-invasive, avoids ionizing radiation and uses a non-nephrotoxic contrast agent.

Prospective multicentre study of the natural history of atherosclerotic renal artery stenosis in patients with peripheral vascular disease

BACKGROUND

Many patients with peripheral vascular disease have coincident renal artery stenosis. The present study characterized the natural history of the condition.

METHODS

Some 98 patients (71 men) with more than 50 per cent atherosclerotic renal artery stenosis (unilateral 64, bilateral 34) were recruited prospectively. Measurements of serum creatinine, blood pressure and renal size were recorded at baseline and every 6 months, for a minimum of 2 years.

RESULTS

Data were available for 85 patients with a minimum follow-up of 2 years. The mean age was 71 (range 51-87) years. All 52 patients with unilateral renal artery stenosis were managed conservatively (group 1); 21 of the 33 patients with bilateral disease had no intervention (group 2) and the remaining 12 had angioplasty or reconstruction (group 3). The overall mortality rate was 32 per cent at 2 years (27 patients) and this was similar in all three groups. In only three patients was death related directly to renovascular disease; coronary disease accounted for the majority of deaths. All three patients who needed dialysis died within 1 year. In survivors from groups 1 and 3 there was a significant increase in serum creatinine concentration at follow-up. Blood pressure did not increase significantly.

CONCLUSION

Patients with renal artery stenosis and peripheral vascular disease had a poor prognosis, but this was not directly attributable to renal failure.

Thin-section multidetector CT angiography of renal artery stents

OBJECTIVE

This study was undertaken as a pilot investigation to compare multidetector CT angiography with conventional catheter angiography for the visualization of the renal artery lumen after renal artery stent placement.

SUBJECTS AND METHODS

CT angiography was performed within 24-48 hr of renal artery stent placement in 15 patients. Two patients had bilateral stents, resulting in a total of 17 stents. CT angiography was performed using a multidetector scanner and a bolus of IV contrast material with the scanning delay determined by a small-volume timing bolus. A volumetric data set was acquired through the stented arteries in the axial plane using a 4.0 x 1.25 mm detector configuration and a pitch of 3:1. The stent lumen diameter, as measured on direct CT angiography and curved multiplanar reformations in both the axial and coronal planes, was compared with that measured on catheter angiography.

RESULTS

The lumina of all 17 stents were well visualized and patent on both CT angiography and catheter angiography. Anatomic definition, including stent position and wall apposition in the renal artery, correlated well with catheter angiography. The diameter of the renal artery stent lumen measured on catheter angiography (mean, 5.9 +/- 1.3 mm) was greater than that on CT angiography (mean stent lumen diameter for direct axial plane was 4.6 +/- 1.0 mm, for curved multiplanar reformations in the axial plane was 4.3 +/- 1.0 mm, and for curved multiplanar reformations in the coronal plane was 4.4 +/- 1.0 mm) in 14 (82%) of 17 stents.

CONCLUSION

CT angiography produced interpretable multiplanar images of the renal artery, even with a metallic stent in place, and was adequate for determining stent patency. Compared with catheter angiography, the intrastent luminal diameter was underestimated in most patients who underwent CT angiography.

Renal vein renin measurements accurately identify renovascular hypertension caused by total occlusion of the renal artery

OBJECTIVE

To assess the usefulness of indexes derived from renal vein renin measurements.

DESIGN

A 12-year prospective study.

SETTING

A tertiary institutional referral centre.

PATIENTS AND METHODS

Between 1988 and 2000, we studied 152 consecutive hypertensive patients with a high pre-test probability of renovascular hypertension (RVH). RVH was diagnosed retrospectively on the basis of reduction in blood pressure after correction of ischaemia at follow-up. Renal vein renin measurements were used to calculate the ratios: Visch/Vctl (renal vein renin ratio; RVRR); Vctl/Viivc; (Visch - Viivc)/Viivc; (Vctl - Viivc)/Viivc, where Visch and Vctl indicate plasma renin activity (PRA) in the ischaemic and contralateral renal veins, respectively, and Viivc denotes PRA in the infrarenal inferior vena cava. A receiver operator characteristics (ROC) curve analysis was used to determine the cut-off value of renal vein renin measurement indexes that provided the best discrimination between patients with and without RVH and to identify patients with RVH caused by total occlusion of the renal artery.

RESULTS

Sixty-seven patients were diagnosed as having RVH: 51 had significant renal artery stenoses (RVH non-occluded) and 16 had total renal artery occlusion (RVH occluded). Of the remaining 85 patients in whom RVH was excluded (non-RVH group), 27 had reno-parenchymal hypertension and 58 had essential hypertension. Of the renal vein renin measurement indexes, only RVRR and (Visch - Viivc)/Viivc in RVH-occluded patients differed significantly (P < 0.005) from those in the non-RVH group and showed the best performance by ROC curve analysis. This analysis also showed that, at any cut-off value, RVRR was far more accurate for identification of RVH-occluded patients than for identification of RVH non-occluded patients, both in the subgroup with unilateral and, even more so, in those with bilateral renal artery lesions. The best trade-off between sensitivity and false-positive rate was provided by cut-off values of 1.55 and 1.70 of the RVRR for identification of non-occluded and occluded RVH, respectively.

CONCLUSIONS

RVRR is more useful for establishing an indication for nephrectomy in patients with renal artery occlusion than for identifying those patients with renal artery stenosis who will benefit from revascularization. In patients with RVH with bilateral renal artery lesions, lateralization of renin secretion occurs only in the presence of total renal artery occlusion. Different cut-off values are necessary for identification of non-occluded and occluded RVH.