eMedicine Specialties > Nephrology > Hypertension and the Kidney

Renal Artery Stenosis: Differential Diagnoses & Workup

Author: Bruce S Spinowitz, MD, FACP, Clinical Professor of Medicine, Weill Medical College of Cornell University; School of Medicine; Associate Chairman, Associate Director and Attending Physician, Department of Medicine, Division of Nephrology, New York Hospital Medical Center Queens; Associate, Nephrology Associates, PC
Coauthor(s): Joanna Rodriguez, MD, Fellow, Department of Internal Medicine, Division of Nephrology, New York Hospital-Queens
Contributor Information and Disclosures

Updated: Jul 15, 2009

Differential Diagnoses

Acute Renal Failure
Nephropathy, Hypersensitivity
Atherosclerosis
Nephrosclerosis
Azotemia
Renovascular Hypertension
Glomerulonephritis, Chronic
Uremia
Hypertension
Hypertension, Malignant

Other Problems to Be Considered

Atherogenesis

Workup

Laboratory Studies

  • Obtain serum creatinine levels to assess the level of renal dysfunction. Serum creatinine levels can be used to calculate an estimated clearance based on the Cockcroft-Gault equation or the MDRD formula developed by Levey and colleagues.4
  • Perform a 24-hour urine collection, or obtain a protein-creatinine ratio on a random void urine specimen, to more accurately assess the level of renal dysfunction and to measure the degree of proteinuria. Vascular renal disease is more often associated with minimal-to-moderate degrees of proteinuria, which are rarely in the nephrotic range.
  • Perform urinalysis to ensure that red blood cells or red blood cell casts (a hallmark of glomerulonephritis) are absent.
  • Perform serologic tests for systemic lupus erythematosus or vasculitis if these conditions are suggested (eg, antinuclear antibodies, C3, C4, antinuclear cytoplasmic antibodies).
  • Studies designed to assess the renin-angiotensin system are of little diagnostic utility in patients with atherosclerotic RVD.
  • Peripheral renin activity reflects volume status in healthy individuals. It may be elevated in patients with renovascular causes of hypertension and in those with essential hypertension. It is equally nondiscriminatory in patients with atherosclerotic RVD with ischemic nephropathy.

Imaging Studies

  • Ultrasound
    • Renal ultrasound is performed frequently in patients with renal dysfunction.
    • Ultrasound is an anatomic, not a functional, test. The only contribution to the entity of renal artery stenosis is a suggestion of the diagnosis when examination results indicate significant asymmetry of kidney size (ie, size discrepancy of >1.5 cm).
    • Additionally, ultrasound may be useful in detecting the presence of a solitary kidney, in which case, renal artery stenosis of that solitary kidney takes on more significant prognostic and therapeutic importance.
  • Radionuclide scanning
    • Use of radionuclide scanning, particularly following a single dose of captopril, is more useful in patients with normal renal function, in whom fibromuscular disease is suspected.
    • Patients with possible ischemic nephropathy (ie, serum creatinine values >2 mg/dL) frequently have associated parenchymal disease or bilateral vascular disease, in which case, the results obtained with scanning are unable to distinguish between parenchymal renal disease and renal artery stenosis/ischemic nephropathy.
  • Duplex ultrasound scanning
    • This noninvasive diagnostic technique combines a B-mode ultrasound image with a pulse Doppler unit to obtain flow velocity data.
    • The technique is noninvasive, relatively inexpensive, and can be used in patients with any level of renal function.
    • The test is very sensitive and specific (98%); however, it is very labor intensive and technician-dependent. Thus, duplex ultrasound scanning may not be available in many medical centers.
    • In a study reported in the New England Journal of Medicine, Radermacher et al were able to use the renal resistance index value to predict the outcome of therapy in patients aggressively treated for renal artery stenosis.5 Specifically, an index of greater than 80, indicating small vessel and large vessel disease, was indicative of a poor response to either angioplasty or surgery with respect to improvement in hypertension, renal function, or kidney survival.
  • Spiral CT angiography
    • This technique involves the use of an intravenous injection of a relatively large dose of iodinated contrast material and allows 3-dimensional reconstruction images of the renal arteries.
    • In 1995, Olbricht et al compared renal CT angiography with arterial digital subtraction angiography for detecting renal artery narrowing of more than 50%.6 The CT technique showed positive and negative predictive values of 91%.
    • Spiral CT angiography is a useful technique that avoids arterial catheterization and produces accurate images of renal artery anatomy. This technique requires iodinated contrast material and significant time to perform the computer-based reconstruction. This technique avoids arterial puncture and, thus, the risk of atheroemboli, but it can be associated with contrast associated nephropathy, particularly in patients with preexisting chronic kidney disease.
  • Magnetic resonance angiography
    • Magnetic resonance angiography (MRA) is a noninvasive technique capable of demonstrating the renal vascular anatomy and revealing physiological information about kidney function. This technique is capable of direct visualization of renal artery lesions without iodinated contrast material and provides a measurement of the absolute blood flow rate, GFR, and renal perfusion rate. Furthermore, MRA can provide accurate serial renal size and volume measurement. The limitations of MRA are its expense and its contraindication in patients with metallic clips, pacemakers, intraocular metallic devices, or other implants.
    • Recent concern regarding the association of gadolinium use with the development of nephrogenic systemic fibrosis in patients with moderate-to-severe renal insufficiency significantly limits the use of this agent and, therefore, this modality for the recognition of anatomic renal artery stenosis.7
    • The technique has been validated only for the stenosis situated in the proximal 3-3.5 cm of renal arteries. Distal renal artery stenosis and segmental renal artery stenosis were generally not analyzed. The sensitivity of MRA was 90% for proximal renal artery stenosis, 82% for main renal artery stenosis, and 0% for segmental stenosis. In a follow-up study, Loubeyre and colleagues examined 46 patients with clinical renal artery stenosis.8 Using a combination of techniques, they determined a sensitivity of 100%, a specificity of 90%, a positive predictive value of 58%, and a negative predictive value of 100% for detecting stenosis of the main, but not accessory or distal, renal artery. These data were obtained with fast-scanning machines using gadolinium enhancement and a breath-holding technique.
    • An additional study compared the accuracy of CT angiography and MRA to digital subtraction angiography and concluded that digital subtraction angiography remains the method of choice to establish a diagnosis.9
  • Conventional arteriography
    • This technique remains the criterion standard for the confirmation and identification of renal artery occlusion in persons with IRD. Specialists can perform renal arteriography by conventional aortography, intravenous subtraction angiography, intra-arterial subtraction angiography, or carbon dioxide angiography.
    • Conventional aortography produces excellent radiographic images of the renal artery, requires an arterial puncture, carries the risk of cholesterol emboli, and uses a moderate amount of contrast material with the risk of contrast-induced acute tubular necrosis (ATN). Low osmolar contrast material can limit the risk of this complication. Complication rates for renal angiography are 6-10% in most series.
    • Intravenous subtraction angiography is sensitive for identifying stenosis of the main renal artery but does not demonstrate accessory or branch renal arteries sufficiently; however, this technique avoids the use of a high volume of contrast and the risk of artery puncture and arterial atherosclerotic emboli.
    • Intra-arterial digital subtraction angiography has a high diagnostic accuracy compared to conventional angiography and is associated with fewer complications, lower doses of contrast, and smaller catheter size.
    • Carbon dioxide angiography is an alternative angiographic contrast agent used in combination with digital subtraction angiography to avoid the risk of conventional nephrotoxic contrast agents in patients with severe renal insufficiency. The images obtained are similar in quality to intra-arterial digital subtraction angiography; however, the technique requires an experienced investigator and a dedicated person to inject the carbon dioxide. Discomfort and inadequate images are potential complications of the procedure.
  • Contrast nephrotoxicity
    • Patients with progressive ischemic nephropathy (ie, underlying chronic renal failure) are at risk for contrast nephrotoxicity and should be informed of this risk prior to any contrast procedure.
    • Contrast nephropathy typically manifests as a brief rise in the serum creatinine level 3-6 days after exposure to radiocontrast and is reported in up to 40% of patients with underlying renal failure.
    • Most patients with contrast nephropathy ultimately recover renal function. Porter reviewed results from nearly 300 patients with contrast nephropathy and concluded that fewer than 10% of these patients required dialysis permanently.
  • Selection of diagnostic tests
    • Once patients are identified as being at high risk for renal artery stenosis, the choice of the best test for diagnosis is controversial.
    • Accurate identification of patients with correctable renovascular hypertension can be difficult with use of standard noninvasive techniques (eg, sonography) because they provide only indirect evidence of the presence of renal artery lesions.
    • On the other hand, invasive techniques with more accurate diagnostic potential can produce a worsening of renal function because of contrast toxicity and complications related to the procedures themselves (eg, arterial puncture, catheter-induced atheroembolism).
    • Gilfeather et al performed a study evaluating conventional angiography versus gadolinium-enhanced MRA in 54 patients and 107 kidneys.10 The study showed that in 70 kidneys (65%), the average degree of stenosis reported by readers of both modalities differed by 10% or less. In 22 cases (21%), MRA overestimated the degree of stenosis by more than 10% relative to the results of conventional angiography; in 15 cases (14%), MRA underestimated the stenosis by more than 10%.
    • The obvious advantages of conventional angiography are its ability to determine the clinical importance of suggestive lesions and the ability to concurrently perform endovascular therapy. In addition, the determination of the pressure gradient across a stenotic lesion may be helpful in determining the clinical significance of a lesion.11 However, specialists should weigh these advantages against the higher cost and greater morbidity of conventional angiography. The slightly inferior variability of MRA in diagnostic interpretation further supports the use of this technique as potentially the most appropriate tool for screening patients strongly suggested to have atherosclerotic RVD.
    • Incidental atherosclerotic renovascular disease is often discovered in patients at the time of cardiac angiography. The impact of this finding on a patient’s outcome and, therefore, on the need to dilate and stent the renal vessel, the so-called "drive-by" percutaneous transluminal renal angioplasty with stenting (PTRAS), is the subject of intense debate.12,13,14

More on Renal Artery Stenosis

Overview: Renal Artery Stenosis
Differential Diagnoses & Workup: Renal Artery Stenosis
Treatment & Medication: Renal Artery Stenosis
Follow-up: Renal Artery Stenosis
References
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References

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Further Reading

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Keywords

renal artery stenosis, RAS, renovascular disease, ischemic nephropathy, atherosclerotic renovascular disease, renovascular hypertension, chronic renal insufficiency, end-stage renal disease, ESRD, atherosclerosis, ATH, RVD, renal artery occlusion, renal disease, kidney disease, ischemic renal disease, renal artery lesions

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Contributor Information and Disclosures

Author

Bruce S Spinowitz, MD, FACP, Clinical Professor of Medicine, Weill Medical College of Cornell University; School of Medicine; Associate Chairman, Associate Director and Attending Physician, Department of Medicine, Division of Nephrology, New York Hospital Medical Center Queens; Associate, Nephrology Associates, PC
Bruce S Spinowitz, MD, FACP is a member of the following medical societies: American College of Physicians, American Society of Nephrology, International Society for Peritoneal Dialysis, International Society of Nephrology, and Renal Physicians Association
Disclosure: AMAG Pharmaceuticals Grant/research funds Independent contractor; Roche Grant/research funds Independent contractor; Amgen Grant/research funds Independent contractor; Affymax Grant/research funds Independent contractor; Ortho Biotech Grant/research funds Independent contractor

Coauthor(s)

Joanna Rodriguez, MD, Fellow, Department of Internal Medicine, Division of Nephrology, New York Hospital-Queens
Disclosure: Nothing to disclose.

Medical Editor

Donald A Feinfeld, MD, FACP, FASN, Consulting Staff, Division of Nephrology & Hypertension, Beth Israel Medical Center
Donald A Feinfeld, MD, FACP, FASN is a member of the following medical societies: American Academy of Clinical Toxicology, American Society of Hypertension, American Society of Nephrology, and National Kidney Foundation
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Eleanor Lederer, MD, Consulting Staff, Louisville VA Hospital; Professor of Medicine; Interim Chief of Nephrology; Director of Nephrology Training Program; Director, Metabolic Stone Clinic; Director of Outpatient Clinics, Kidney Disease Program, University of Louisville School of Medicine
Eleanor Lederer, MD is a member of the following medical societies: American Association for the Advancement of Science, American Federation for Medical Research, American Society for Biochemistry and Molecular Biology, American Society for Bone and Mineral Research, American Society of Nephrology, American Society of Transplantation, International Society of Nephrology, Kentucky Medical Association, National Kidney Foundation, and Phi Beta Kappa
Disclosure: Nothing to disclose.

CME Editor

Rebecca J Schmidt, DO, FACP, FASN, Professor of Medicine, Section Chief, Department of Medicine, Section of Nephrology, West Virginia University School of Medicine
Rebecca J Schmidt, DO, FACP, FASN is a member of the following medical societies: American College of Osteopathic Internists, American College of Physicians, American Medical Association, American Society of Nephrology, International Society of Nephrology, National Kidney Foundation, Renal Physicians Association, and West Virginia State Medical Association
Disclosure: Abbott Grant/research funds Speaking and teaching; Genzyme Honoraria Consulting; Amgen Honoraria Speaking and teaching; Ortho Biotech Honoraria Speaking and teaching

Chief Editor

Vecihi Batuman, MD, FACP, FASN, Professor of Medicine, Section of Nephrology-Hypertension, Tulane University School of Medicine; Chief, Medicine Service, Southeast Louisiana Veterans Health Care System
Vecihi Batuman, MD, FACP, FASN is a member of the following medical societies: American College of Physicians, American Society of Hypertension, American Society of Nephrology, and International Society of Nephrology
Disclosure: Nothing to disclose.

 
 
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