What is the recommended workup for a patient with suspected fibromuscular dysplasia?

Workup for Suspected Fibromuscular Dysplasia

For patients with suspected fibromuscular dysplasia (FMD), the recommended initial diagnostic workup should include duplex ultrasonography followed by either computed tomographic angiography (CTA) or magnetic resonance angiography (MRA), with catheter angiography reserved for inconclusive cases or when intervention is planned. 1

Clinical Presentation and Initial Assessment

When evaluating a patient with suspected FMD, focus on:

• Demographics: Most common in women aged 25-50 years, though can occur in both genders at any age 1
• Presenting symptoms: Hypertension (especially in young women), stroke, TIA, headaches
• Physical examination: Listen for bruits over carotid, epigastric, and flank regions
• Family history: Hypertension and FMD in relatives

Diagnostic Imaging Algorithm

Step 1: Initial Screening

• Duplex ultrasonography is recommended as the first-line screening test (Class I recommendation, Level of Evidence B) 1
  • Advantages: Non-invasive, no radiation, widely available
  • Limitations: Operator-dependent, limited sensitivity (28%) compared to angiography 2
  • Target areas: Renal arteries, carotid arteries

Step 2: Cross-sectional Imaging

If ultrasound is positive or clinical suspicion remains high:

• Computed Tomographic Angiography (CTA)

  • Recommended for patients with normal renal function 1
  • Highest sensitivity (84.2%) among non-invasive modalities 2
  • Superior to MRA for visualizing vascular lesions in FMD 1
  • Can identify the classic "string of beads" appearance and other patterns

• Magnetic Resonance Angiography (MRA)

  • Recommended as an alternative screening test (Class I recommendation, Level of Evidence B) 1
  • Better sensitivity (62.5%) than ultrasound 2
  • Particularly useful for evaluating cystic adventitial disease 1
  • Preferred in patients with renal dysfunction to avoid iodinated contrast

Step 3: Definitive Imaging

• Catheter Angiography
  • Recommended when clinical suspicion is high and noninvasive tests are inconclusive (Class I recommendation, Level of Evidence B) 1
  • Gold standard for diagnosis
  • Only modality that can adequately visualize distal vessel disease 2
  • Should be performed as part of initial workup when renovascular FMD is strongly suspected, regardless of findings on other imaging 2

Arterial Beds to Evaluate

Since FMD can affect multiple vascular beds, consider comprehensive evaluation:

1. Renal arteries - Most commonly affected (80-85% of cases) 1
2. Cervical arteries (carotid and vertebral)
3. Other arterial beds if clinically indicated:
   • Mesenteric arteries
   • Extremity arteries
   • Intracranial arteries

Laboratory Evaluation

• Basic metabolic panel to assess renal function
• For patients with hypertension: Consider screening for primary aldosteronism with plasma aldosterone and renin activity 1

What Not to Include in Workup

The following tests are not recommended for FMD diagnosis (Class III recommendations) 1:

• Captopril renal scintigraphy
• Selective renal vein renin measurements
• Plasma renin activity
• Captopril test (measurement of plasma renin activity after captopril)

Special Considerations

• Multifocal FMD: Characterized by the classic "string of beads" appearance (80% of cases) 1
• Unifocal FMD: May present as a single stenosis, more challenging to distinguish from other causes
• Complications: Screen for associated aneurysms and dissections, which are common in FMD patients 3
• Pediatric patients: Angiography should be performed regardless of findings on other imaging modalities 2

Follow-up Imaging

After diagnosis, regular surveillance imaging is important to monitor disease progression:

• Annual noninvasive imaging of affected arteries is reasonable initially 4
• More frequent imaging may be needed in the first few years after diagnosis 4

Remember that FMD is often underdiagnosed, and early detection can significantly improve outcomes by allowing for timely intervention and prevention of complications.