What is the initial management approach for patients with fibromuscular dysplasia (FMD) of renal arteries?

Initial Management of Fibromuscular Dysplasia of Renal Arteries

For patients with fibromuscular dysplasia (FMD) of renal arteries, initial management should include appropriate medical therapy to reduce blood pressure, followed by percutaneous transluminal renal angioplasty (PTRA) without stenting as the treatment of choice for symptomatic cases. 1, 2

Diagnostic Approach

• FMD is a nonatherosclerotic, noninflammatory vascular disease that primarily affects women between ages 20-60, though it can occur in any age group 3, 4
• Initial screening tests should include duplex ultrasonography, computed tomographic angiography (CTA), or magnetic resonance angiography (MRA) 2
• Catheter angiography remains the gold standard for diagnosis when clinical suspicion is high and noninvasive tests are inconclusive 2
• The classic angiographic appearance is the "string-of-beads" pattern, observed in >80% of cases, typically involving the middle and distal two-thirds of the main renal artery 3

Initial Management Algorithm

Step 1: Medical Therapy

• All patients with FMD should receive appropriate medical therapy to reduce blood pressure as first-line treatment 1, 2
• Renin-angiotensin system (RAS) blockers (ACE inhibitors or ARBs) are the drugs of choice when percutaneous intervention is not immediately performed 1, 2
• Careful monitoring of renal function is required with RAS blockers, as they can cause acute renal failure in patients with bilateral stenoses or stenosis in a solitary functioning kidney 1

Step 2: Evaluation for Revascularization

• Consider PTRA without stenting for patients with:
  • Hypertension with hemodynamically significant renal artery stenosis due to FMD 1
  • Resistant hypertension despite optimal medical therapy 1
  • Unexplained unilaterally small kidney 1
  • Bilateral renal artery stenosis or unilateral stenosis in a solitary viable kidney 1

Step 3: Revascularization Procedure

• PTRA without stenting is the first-line revascularization technique for symptomatic renal FMD (Class IIa recommendation) 1, 2
• Stenting should be reserved only for management of dissection or balloon angioplasty failure 2
• Open surgical revascularization should be considered only in cases with complex aneurysms, complex lesions involving arterial bifurcation or branches, or failed endovascular therapy 2

Outcomes and Prognosis

• Technical success rates for PTRA approach 100% 5
• Hypertension cure or improvement occurs in approximately 46% of patients after angioplasty 6
• Factors associated with better outcomes include:
  • Duration of hypertension <8 years 5
  • Normal renal function (creatinine <1.5 mg/dL) 5
  • Ipsilateral kidney size >9 cm 5
  • Normal contralateral kidney function 5
• Restenosis rates are approximately 28% at 5 years 5

Special Considerations

• FMD is now recognized as a systemic disease affecting multiple vascular beds, requiring evaluation of other arterial territories, particularly carotid and vertebral arteries 1, 2
• Aneurysm formation is a potential complication of FMD and should be assessed during diagnostic workup 2, 3
• The natural history of FMD is relatively benign, with progression occurring in only a minority of patients 7
• Consider the possibility of familial FMD, which occurs in approximately 10% of cases 3

Pitfalls and Caveats

• Do not confuse FMD with atherosclerotic renal artery stenosis, which requires different management approaches 1
• Avoid stenting in FMD unless there is dissection or balloon angioplasty failure 2
• Monitor renal function carefully when using ACE inhibitors or ARBs in patients with bilateral renal artery stenosis 1
• Be aware that FMD can affect multiple vascular beds simultaneously, requiring comprehensive vascular evaluation 1, 2
• Consider the patient's age and duration of hypertension when predicting outcomes, as these factors significantly influence treatment success 6, 5