Effectiveness of Management Strategies for Renal Artery Stenosis: A Systematic Review

Context Is medical therapy as effective as revascularization for atherosclerotic renal artery stenosis? Contribution This systematic review found no trials that compared aggressive medical therapy and angioplasty with stent in adults with atherosclerotic renal artery stenosis. Some evidence suggested similar kidney outcomes but better blood pressure outcomes with angioplasty, particularly in patients with bilateral renal disease. Weak evidence suggested no large differences in mortality or cardiovascular events between medical and revascularization treatments. No evidence directly compared adverse event rates between treatments. Implications Available evidence comparing benefits and harms of modern treatments for atherosclerotic renal artery stenosis is sparse and inconclusive. The Editors Renal artery stenosis is defined as narrowing of the renal artery lumen. Atherosclerosis, which usually involves the ostium and proximal third of the main renal artery and the perirenal aorta, accounts for 90% of cases of renal artery stenosis (1). Atherosclerotic renal artery stenosis is increasingly common in aging populations, particularly elderly people with diabetes, hyperlipidemia, aortoiliac occlusive disease, coronary artery disease, or hypertension. Atherosclerotic renal artery stenosis is a progressive disease that may occur alone or in combination with hypertension and ischemic kidney disease (1). Although the prevalence of atherosclerotic renal artery stenosis is poorly defined, it may vary from 30% among patients with coronary artery disease identified by angiography (2) to 50% among elderly people or those with diffuse atherosclerotic vascular diseases (3). In the United States, 12% to 14% of patients in whom dialysis is initiated have been found to have atherosclerotic renal artery stenosis (4). Most authorities consider blood pressure control, preservation or salvage of kidney function, and prevention of flash pulmonary edema to be important treatment goals for patients with atherosclerotic renal stenosis. Treatment options include medication alone or revascularization of the stenosed artery or arteries. Combination therapy with multiple antihypertensive agents, often including angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers, calcium-channel blockers, and -blockers, is frequently prescribed. Some clinicians also use statins to decrease low-density lipoprotein cholesterol levels and antiplatelet agents, such as aspirin or clopidogrel, to reduce the risk for thrombosis. The current standard for revascularization in most patients is percutaneous transluminal angioplasty with stent placement across the stenosis. Angioplasty without stent placement is less commonly used. Revascularization by surgical reconstruction is generally done only in patients with complicated renal artery anatomy or in those who require pararenal aortic reconstructions for aortic aneurysms or severe aortoiliac occlusive disease. The American College of Cardiology and the American Heart Association recently published guidelines for management of patients with peripheral arterial disease, including renal artery stenosis (5, 6). Although these guidelines provide recommendations about which patients should be considered for revascularization, considerable uncertainty remains about which intervention provides the best clinical outcomes. Among patients treated with medical therapy alone, experts are concerned about the risk for deterioration of kidney function and worsening cardiovascular morbidity and mortality. Revascularization procedures may provide immediate improvement in kidney function and blood pressure, but they are invasive interventions that could result in substantial morbidity or death, and because of the risk for restenosis the durability of their benefits is questioned. Although evidence regarding the optimal management of atherosclerotic renal artery stenosis appears uncertain, a Medicare claims analysis found that the rate of percutaneous renal artery revascularization has rapidly increased between 1996 and 2000, with the number of interventions increasing from 7660 to 18520 (7). To determine which patients, if any, with atherosclerotic renal artery stenosis would most benefit from angioplasty with stent placement, as opposed to continued aggressive medical treatment, the National Institutes of Health has sponsored the large, multicenter Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial. Participants are currently being enrolled in the trial, and results should be reported in 2010. Meanwhile, the Agency for Healthcare Research and Quality, under Section 1013 of the Medicare Modernization Act, commissioned a review asking key questions related to the effectiveness of aggressive medical therapy compared with renal artery angioplasty with stent placement. However, because no published evidence directly compared angioplasty with stent placement and aggressive medical treatment with currently available drugs, the review covered direct comparisons of revascularization, including angioplasty with or without stent placement and surgery, and various medical regimens and indirect comparisons of angioplasty (with stent placement) and surgical interventions, various medical therapies, and natural history (8). Methods Data Sources and Selection To identify articles relevant to several key questions, we searched the MEDLINE database from inception to 6 September 2005 for studies involving adults with atherosclerotic renal artery stenosis. The Figure shows the search and selection process. The full technical report (available at www.effectivehealthcare.ahrq.gov/reports/final.cfm) provides a more detailed description of the study methods. We also reviewed reference lists of related systematic reviews, selected narrative reviews, and primary articles, and we invited domain experts to provide additional citations. We combined search terms for renal artery stenosis, renal hypertension, and renal vascular disease, and we limited the search to English-language articles of studies in adult humans that had relevant research designs. We included peer-reviewed primary studies of adult patients treated for atherosclerotic renal artery stenosis and excluded studies that evaluated patients with renal artery stenosis in the setting of a transplanted kidney, renal artery aneurysm requiring repair, aortic disease requiring invasive intervention, or concurrent cancer or patients who had had previous surgical or angioplasty interventions for renal artery stenosis. We included only studies that reported outcomes of interest (mortality rate, kidney function, blood pressure, and cardiovascular events) at 6 months or more after the initial intervention. We excluded studies in which more than 20% of patients had renal artery stenosis due to other causes. We categorized studies according to whether they evaluated medical treatment, angioplasty, or surgical revascularization or were natural history studies, and by whether they directly compared interventions. Figure. Search and selection of studies for review. *Prospective study; enrolled 10 or more patients; study duration at least 6 months. Prospective study; angioplasty included stent placement; enrolled 30 or more patients; study duration at least 6 months; patients recruited in 1993 or later; patients did not have previous angioplasty. One study has data both for direct comparison of medical treatment to angioplasty and for natural history. Any study design; enrolled 10 or more patients; study duration at least 6 months. Studies with surgical intervention must have recruited patients in 1993 or later. Any study design; enrolled 10 or more patients; study duration at least 6 months; patients recruited in 1993 or later. Any study design; enrolled 100 or more patients (10 or more if the study was prospective); study duration at least 6 months; patients recruited in 1993 or later. We used different eligibility criteria for studies of different interventions, based on the varying number of studies available for each intervention and the relevance of the intervention to current practice. We included all direct comparisons of medical treatment with angioplasty and all uncontrolled (cohort) studies of medical treatment that had at least 10 patients in each group, regardless of study design. For angioplasty, surgical, or natural history studies, we included only those in which at least some patients were recruited in 1993 or later, after the publication of the Fifth Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. These guidelines marked a substantial change from previous guidelines in treatment recommendations for hypertension, including more aggressive blood pressure targets (9). In addition, at this time point, angiotensin-converting enzyme inhibitors began to be used more routinely in the treatment of patients with severe hypertension. We included only angioplasty studies that used stent placement, were prospective, and had at least 30 patients and retrospective surgery studies that included at least 100 patients. Any prospective surgery study that otherwise met criteria was eligible. Data Extraction and Quality and Applicability Assessments Data from each study were extracted by one of the authors and confirmed by another. The extracted data included information about patient samples, interventions, outcomes, adverse events, study design, quality, and applicability. We used predefined criteria to grade study quality as good, fair, or poor; study applicability as high, moderate, or low; and the strength of the overall body of evidence as robust, acceptable, or weak (Appendix Table). Each included study was graded by at least 2 of the authors. Appendix Table. Study Quality, Applicability, and Strength of Evidence Ratings Data Synthesis Because the study designs, participants, interventions, and reported outcome measures varied marke