What are the clinical presentation, diagnostic workup, and management recommendations for fibromuscular dysplasia?

Fibromuscular Dysplasia: Clinical Presentation, Diagnosis, and Management

Clinical Presentation

FMD is a nonatherosclerotic, noninflammatory vascular disease that predominantly affects middle-aged women and presents most commonly with hypertension (renal involvement) or neurological symptoms (cerebrovascular involvement). 1

Renal Artery FMD

• Hypertension is the hallmark presentation, particularly new-onset hypertension in patients aged ≤35 years 2
• Severe hypotension or azotemia provoked by ACE inhibitors or ARBs suggests hemodynamically significant renal artery stenosis 2
• Medial fibroplasia (80-85% of renal FMD cases) typically affects the middle and distal two-thirds of the main renal artery, unlike atherosclerotic disease which affects the ostial and proximal segments 2
• Bilateral renal artery involvement is common in women aged 25-50 years 2

Cerebrovascular FMD

• Stroke or TIA from reduced blood flow or thromboembolism 1, 2
• Carotid or vertebral artery dissection, which can occur spontaneously 1, 2
• Horner syndrome from carotid involvement 1, 2
• Cranial nerve palsies 1, 2
• Subarachnoid hemorrhage from aneurysmal rupture 1, 2
• Headaches and pulsatile tinnitus are common symptoms 3

Systemic Manifestations

• FMD is a systemic arterial disease requiring comprehensive vascular evaluation, as it can affect multiple vascular beds including renal, carotid, vertebral, iliac, and other arteries 4, 5, 2
• Approximately 13.4% of FMD patients experience TIA, 12% experience cervical artery dissection, and 9.8% have had a stroke 4

Diagnostic Workup

Duplex ultrasonography should be performed as the initial screening test, followed by CT angiography or MR angiography from head to pelvis to identify the systemic nature of the disease. 4, 2

Initial Screening

• Duplex ultrasonography as the initial screening test (Class I recommendation) 4, 2
• CT angiography in patients with normal renal function 2
• MR angiography as an alternative screening modality 2
• Renal artery Doppler ultrasound with bilateral assessment of renal arterial resistive index for suspected renovascular hypertension 4

Confirmatory Imaging

• Catheter-based contrast angiography is the gold standard and should be performed when clinical suspicion is high and noninvasive tests are inconclusive 4, 2
• CT angiography or MR angiography from head to pelvis should be performed at diagnosis to identify involvement in multiple vascular beds 5, 2

Characteristic Imaging Findings

• "String of beads" appearance is pathognomonic for medial fibroplasia, where the diameter of the beading is larger than the normal arterial diameter 2, 6
• Focal stenosis appearing as concentric or tubular narrowing (intimal fibroplasia) 2
• Weblike lesions that may obstruct flow 2
• Aneurysmal dilation 2
• Arterial elongation, kinking, and coiling 1

Tests NOT Recommended

• Do NOT use captopril renal scintigraphy, selective renal vein renin measurements, or plasma renin activity as screening tests (Class III recommendation) 4, 5

Additional Laboratory Assessment

• Very elevated renin levels may raise suspicion for renovascular hypertension 4, 5
• Morning plasma aldosterone and plasma renin activity to screen for primary aldosteronism, as resistant hypertension is common in FMD 5
• 24-hour urinary sodium or sodium-to-creatinine ratio in morning urine when evaluating for renovascular hypertension 4

Surveillance Imaging

• Annual noninvasive imaging of the carotid arteries is reasonable initially to detect changes in disease extent or severity (Class IIa recommendation) 4, 5, 2
• Imaging frequency may be reduced once stability has been confirmed over time 4, 5, 2
• Screen for aneurysms as they represent a potential complication requiring surveillance or intervention 5

Management

All patients with FMD require antiplatelet therapy and blood pressure control as the foundation of treatment, regardless of whether they undergo revascularization. 5

Universal Medical Therapy (All Patients)

Antiplatelet Therapy

• Start antiplatelet therapy (aspirin or clopidogrel) to prevent thromboembolic complications in all patients with FMD 5
• Antiplatelet therapy is recommended even for asymptomatic patients 1

Blood Pressure Management

• RAS blockers (ACE inhibitors or ARBs) are the drugs of choice when percutaneous intervention is not immediately feasible 4, 5
• Monitor renal function carefully when using RAS blockers, particularly in bilateral stenoses or solitary functioning kidney, as acute renal failure can occur 5
• Alternative antihypertensive agents include calcium channel blockers (dihydropyridine or non-dihydropyridine) and alpha-receptor antagonists if RAS blockers are contraindicated 5

Renal Artery FMD: Revascularization Strategy

Percutaneous transluminal renal angioplasty (PTRA) without stenting is the first-line revascularization technique for symptomatic renal FMD. 4, 5

Indications for Revascularization

• Refractory hypertension despite medical management 5
• Worsening renal function 5
• Recent onset hypertension in young patients with an audible bruit 5
• Hemodynamically significant renal artery stenosis (Class IIa recommendation) 5

Revascularization Technique

• PTRA without stenting should be performed as first-line therapy 4, 5
• Stenting should be reserved ONLY for dissection or balloon angioplasty failure 4, 5
• Procedures should be performed in experienced centers due to technical complexity and risk of complications 5
• Open surgical revascularization should be reserved for cases with complex aneurysms, complex lesions involving arterial bifurcation or branches, or failed endovascular therapy 4, 5

Cerebrovascular FMD Management

For symptomatic cerebrovascular FMD, antiplatelet therapy is the primary treatment; carotid angioplasty may be reasonable for recurrent ischemic events despite optimal medical management. 5

Symptomatic Patients

• Carotid angioplasty with or without stenting is reasonable for patients with retinal or hemispheric cerebral ischemic symptoms related to FMD of the ipsilateral carotid artery (Class IIa recommendation) 5
• Consider carotid angioplasty for recurrent ischemic stroke without other attributable causes despite optimal medical management 5
• Both surgical revascularization and endovascular approaches have been successful in alleviating ischemic symptoms 1

Asymptomatic Patients

• Do NOT revascularize asymptomatic carotid FMD, regardless of stenosis severity (Class III recommendation) 5
• Antiplatelet therapy and sequential imaging are recommended for asymptomatic patients 1

Cervical Artery Dissection Associated with FMD

• Antiplatelet therapy is reasonable for patients with dissection and FMD but no intraluminal thrombus, over anticoagulation 5
• The association of carotid dissection with FMD is approximately 15% 1

Critical Pitfalls to Avoid

• Never use stents as first-line therapy for renal FMD—balloon angioplasty alone is superior 5
• Never assume isolated disease—always evaluate multiple vascular beds as FMD is systemic 5
• Never revascularize asymptomatic carotid lesions—medical management is appropriate 5
• Monitor renal function closely when using RAS blockers in bilateral disease to prevent acute kidney injury 5
• Control blood pressure aggressively to prevent arterial dissection, which can occur in multiple vascular territories 5
• Do NOT use corticosteroids—they can directly and rapidly harm the vascular wall, aggravating the lesions 7

Long-Term Management

• Regular blood pressure monitoring and renal function assessment in all patients with renal artery FMD 5
• Refer to specialized centers for dedicated multidisciplinary FMD management 5
• Comprehensive vascular evaluation at diagnosis with CT or MRI angiography from head to pelvis 5