Renal Artery Stenosis

Key Features

Essentials of Diagnosis

• Produced by atherosclerotic occlusive disease (most patients) or fibromuscular dysplasia

• Hypertension

• Acute kidney injury with initiation of angiotensin-converting enzyme (ACE) inhibitor therapy if stenosis is bilateral

General Considerations

• Atherosclerotic ischemic renal disease

  • Accounts for most cases of renal artery stenosis

  • Occurs most commonly in persons older than age 45 years with additional risk factors such as CKD, diabetes mellitus, and tobacco use

• Fibromuscular dysplasia is a less common cause

Demographics

• Approximately 5% of Americans with hypertension suffer from renal artery stenosis

Clinical Findings

Symptoms and Signs

• Refractory hypertension

• New-onset hypertension in older patient

• Pulmonary edema with poorly controlled blood pressure

• Acute kidney injury upon starting an ACE inhibitor or an angiotensin receptor blocker (ARB)

• Abdominal bruit on affected side

Differential Diagnosis

• Hypertensive nephrosclerosis

• Primary hyperaldosteronism

• Cushing syndrome

• Coarctation of the aorta

Diagnosis

Laboratory Tests

• Elevated blood urea nitrogen and serum creatinine

• Hypokalemia

  • May be found in patients with bilateral renal artery stenosis

  • Reflects activation of the renin-angiotensin-aldosterone system in response to reduced blood flow (a "prerenal" state)

Imaging Studies

• Abdominal ultrasound shows asymmetric kidney size

• Initial screening tests: Doppler ultrasonography, CT angiography, and magnetic resonance angiography (MRA)

• Doppler ultrasonography

  • Highly sensitive and specific (85% and 92%, respectively, in a meta-analysis of 88 studies) and relatively inexpensive test

  • Poor choice for patients who are obese, unable to lie supine, or have interfering bowel gas patterns

• CT angiography

  • A noninvasive procedure

  • Consists of intravenous contrast injection with digital subtraction arteriography

  • Sensitivity ranges from 77% to 98% and specificity from 90% to 94%

• MRA

  • Excellent but expensive test

  • Sensitivity is 77% to 100% and specificity ranges from 71% to 96%

  • Turbulent blood flow can cause false-positive results

  • Its imaging agent, gadolinium, has been associated with nephrogenic systemic fibrosis

• Renal angiography

  • Gold standard for diagnosis; performed after an initial imaging test result is abnormal

  • Fibromuscular dysplasia has characteristic "beads-on-a-string" appearance

  • CO₂ subtraction angiography is used when risk of dye nephropathy exists (eg, diabetic patients with kidney injury)

  • Risk of atheroembolic phenomena after angiography ranges from 5% to 10%

Treatment

Medications

• Antihypertensive agents, avoiding ACE inhibitors and ARBs

Surgery

• Surgical bypass (revision) is an option for atherosclerotic ischemic renal disease

Therapeutic Procedures

• Angioplasty

  • Might reduce number of antihypertensive medications

  • However, does not significantly change the progression of kidney dysfunction

• Stenting

  • Produces significantly better results than angioplasty

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