Renal Artery Stenosis

Renal artery stenosis (RAS) is a frequently overlooked cause of uncontrolled hypertension and progressive deterioration of renal function. A high index of suspicion is needed to diagnose renal artery stenosis. Stenotic lesions are commonly produced by fibromuscular dysplasia or atherosclerotic plaque. Screening high risk patients can disclose lesions which, if treated, may result in improved blood pressure control as well as preservation of renal function. Revascularization of these patients is associated with preservation of renal function as well as better control of hypertension, unstable angina, and congestive heart failure.

Who should be screened for RAS? Screening should be reserved for hypertensive patients with: 1) the onset of hypertension before 30 and after 55 years, 2) malignant or accelerated hypertension, 3) the sudden exacerbation of hypertension in a previously well controlled patient, 4) evidence of diffuse atherosclerosis, 5) an epigastric bruit, 6) azotemia induced by ACE inhibitor, 7) unexplained azotemia, 8) an unilateral small kidney, and 9) flash pulmonary edema in the presence of normal left ventricular function.

What is the most effective means of screening for RAS? Many testing modalities have employed over the years. Screening should start with non-invasive testing. Currently, duplex ultrasonography provides the safest non-invasive method to assess kidney size and structure as well as provide a functional evaluation of the renal arteries and the severity of stenosis. Sensitivity and specificity usually exceed 90% in dedicated vascular laboratories. This test is safe for all patients and is useful for serial follow-up exams.  MR angiography and spiral CT angiography are very valuable but are less useful as screening modalities due to cost considerations and availability.

Treatment of RAS patients with fibromuscular dysplasia is best accomplished by percutaneous angioplasty. A significant improvement in blood pressure control can be expected. Patients with atherosclerotic disease initially require intensive medical therapies to control risk factors (lipid lowering, anti-platelet therapies, antihypertensives, etc.). Revascularization is best accomplished by angioplasty plus stenting. Several studies have shown better preservation of renal function and control of hypertension in patients treated in this manner.

Our Vascular Ultrasound Evaluation laboratory (VUE) has been very useful in screening patients for the diagnosis of RAS.