The articles in this supplement highlight several of the key issues and problems in the diagnosis and management of renal artery stenosis. Renal artery stenosis is a common, often overlooked, disorder that is associated with significant morbidity and mortality. Approximately 5–10% of individuals aged >= 65 years have renal artery stenosis, and this prevalence increases to 20–30% in selected high-risk subsets of patients.

Most renal artery stenosis is due to atherosclerosis, and the epidemiology of this type of stenosis is similar to that of coronary artery disease. Patients are older, and more men than women develop atherosclerotic renal artery disease. Ultimately, both genders are significantly affected. In contrast, renal artery stenosis due to fibromuscular dysplasia is more common in younger women and children. Atherosclerotic renal artery stenosis is a progressive disorder that leads to hypertension, congestive heart failure, pulmonary edema, renal dysfunction, and end-stage renal disease. Without revascularization, survival is generally < 10 years with high-grade unilateral disease, and < 5 years with high-grade bilateral disease. However, not all lesions are severe or even clinically relevant. Detection of renal artery stenosis, in and of itself, is not an indication for revascularization.

The first step in detecting renal artery stenosis is recognizing the potential clinical clues for this disorder (Table 1). Since atherosclerosis is responsible for producing most cases of renal artery stenosis, any indication of systemic atherosclerosis, such as ischemic heart disease, cerebrovascular disease, or peripheral arterial disease (occlusive or aneurismal), significantly increases the probability of detecting atherosclerotic renovascular disease. Finally, renovascular disease should be suspected in any patient with symptoms potentially related to deteriorating kidney function, including progressive hypertension (especially in patients with previously well-controlled hypertension), azotemia, congestive heart failure, or unexplained pulmonary edema. Hypertension that presents in uncommon scenarios, is treatment resistant, or has a sudden change in status is frequently caused by renovascular disease.

Once renal artery stenosis is suspected, the next step is confirming the diagnosis. Depending on local expertise, the two most common non-invasive diagnostic evaluations are duplex ultrasonography and magnetic resonance imaging. Computed tomographic angiography is an emerging non-invasive technique that requires contrast enhancement and significant external beam radiation. Duplex ultrasonography is a challenging test and, like all procedures, its quality depends on the expertise of the technician and the interpreting physician. With appropriate training and experience, this test can be mastered. It is not an examination solely performed in academic medical centers. Duplex ultrasonography is ideal for serial evaluations before and after intervention (Fig. 1). Serial magnetic resonance imaging is not cost-effective, and it is not feasible following metallic stent placement in the renal artery.

These non-invasive evaluations can be supplemented by abdominal aortography in those patients who are candidates for revascularization or in those patients already undergoing arteriography for other reasons (unstable coronary syndromes, peripheral arterial disease, etc.). Because of the inherent risks of catheterization, this procedure is not indicated as the initial diagnostic evaluation in most patients. However, it should be performed in patients who are already undergoing catheterization for other atherosclerotic disorders and who would potentially benefit from identifying this disorder. These patients have a high prevalence of renovascular disease, and additional angiography adds little to the overall risk of the procedure.

The goal of treatment is to reduce mortality by improving blood pressure and preserving renal function. In patients with a hemodynamically significant renal artery stenosis, indications for revascularization include difficult-to-control hypertension, recurrent pulmonary edema, and progressive deterioration in renal function without another definable etiology. Since repeated observations over time are required to establish any of these parameters, revascularization is not always indicated at the time of initial diagnosis, especially when this diagnosis occurs during a diagnostic arteriogram to identify another atherosclerotic disorder.

The extent of disease relative to overall functioning renal mass is another important consideration that influences treatment decisions. Unilateral stenosis with two functioning kidneys is less clinically significant than unilateral stenosis to a solitary kidney or bilateral stenosis. Those patients require more aggressive surveillance and treatment. For example, revascularizing the kidneys of an 81-year-old woman with a rising serum creatinine level of 2.3 mg/dl and well-controlled, long-standing hypertension is probably not going to significantly alter her life expectancy if she has unilateral disease and two functioning kidneys. In contrast, this revascularization may preserve or improve her renal function and prolong her life if she had severe renal artery stenosis in the artery or arteries serving her entire functioning renal mass. In similar cases, a careful and thorough discussion of the potential risks and benefits of revascularization is necessary. In patients with global renal artery stenosis, a solitary functioning kidney, and objective deterioration in renal function, there is an approximately 20% probability of eventually needing renal replacement therapy without revascularization. Revascularization has a significant chance of altering this natural history. However, the procedure carries risk (including atheroembolization), and these risks must be considered in each patient to make the optimal decision.

Diagnosis and treatment are also significantly influenced by the etiology of the stenosis. Fibromuscular dysplasia requires a high index of suspicion since it is frequently undetected and leads to a loss of kidney function over time. Renal artery stenosis due to fibromuscular dysplasia can be difficult to detect with non-invasive techniques. The typical location of these stenoses in the mid-to-distal renal artery makes them difficult to image with duplex ultrasonography, and they are frequently overestimated by magnetic resonance imaging. Sudden hypertension in a young woman probably warrants an angiogram regardless of the non-invasive findings. Furthermore, detection of fibromuscular dysplasia represents a clear indication for immediate revascularization. Because revascularization has a high success rate in fibromuscular dysplasia, it is the treatment of choice in association with the appropriate clinical scenario.

The approach to revascularization, whether surgical or endovascular, should be dictated by patient characteristics. An initial surgical repair may be preferable in patients with diffuse renal artery stenoses, branch renal artery disease, or renal artery occlusion in those patients with previous failure of endovascular therapy, and in those who already require abdominal surgery to repair an aortic aneurysm. However, the initial treatment of choice for most patients will be an endovascular repair using percutaneous transluminal renal artery angioplasty with renal artery stenting. All patients with renal artery stenosis, whether revascularized or not, require aggressive and optimal medical therapy and continued longitudinal evaluation of their clinical status and renal artery anatomy

Journal of Hypertension Dec. 2005