Renal Artery Stenosis

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 who have a history of atherosclerotic disease elsewhere

• Other risk factors include

  • Chronic kidney disease

  • Diabetes mellitus

  • Tobacco use

  • Hypertension

• Fibromuscular dysplasia is a less common cause

Demographics

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

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

• Abdominal bruit on affected side

Differential Diagnosis

• Hypertensive nephrosclerosis

• Primary hyperaldosteronism

• Cushing syndrome

• Coarctation of the aorta

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

  • 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 digital subtraction angiography with arteriography

  • Uses a spiral (helical) CT scan with intravenous contrast injection

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

• MRA

  • Excellent but expensive

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

  • Turbulent blood flow can cause false-positive results

  • The imaging agent gadolinium has been associated with nephrogenic systemic fibrosis, which occurs

    • Primarily in patients with GFR < 15 mL/min/1.73 m²

    • Rarely in patients with GFR of 15–30 mL/min/1.73 m² or greater

    • In patients with acute kidney injury

    • In kidney transplant patients

• Renal angiography

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

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

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

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

Medications

• Pharmacologic antihypertensive agents that avoid ACE inhibitors and ACE receptor blockers

Surgery

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

Therapeutic Procedures

• Angioplasty for atherosclerotic ischemic renal disease

  • Might reduce number of antihypertensive medications

  • Equally as effective as, and safer than, surgical revision

• Stenting

  • Produces significantly better results than angioplasty

  • However, blood pressure is equally improved, and serum creatinines are similar at 6 months of observation

• Percutaneous transluminal angioplasty can be curative for fibromuscular dysplasia

Follow-Up

• Monitor blood pressure, kidney function, serum lipids

Complications

• Resistant hypertension

• Chronic kidney disease

When to Refer

• Inability to control hypertension

• Kidney injury

When to Admit

• Malignant hypertension