What is May-Turner syndrome?

May-Thurner Syndrome

May-Thurner syndrome (MTS) is a vascular anatomic variant characterized by compression of the left common iliac vein by the right common iliac artery against the lumbar spine, resulting in venous outflow obstruction that can lead to deep vein thrombosis (DVT) and postthrombotic syndrome. 1

Epidemiology and Pathophysiology

• Affects approximately 22% of the general population 2
• More commonly diagnosed in females than males 3, 4
• Typically presents in young adults, though can be diagnosed at any age 5
• The anatomical compression creates:
  • Chronic venous stasis
  • Endothelial injury
  • Hypercoagulability (Virchow's triad)
  • Development of venous spurs and intimal hyperplasia at compression sites

Clinical Presentation

MTS typically presents with:

• Left-sided lower extremity DVT (most common presentation) 1, 6
• Recurrent unprovoked DVTs of the left lower extremity despite adequate anticoagulation 5, 3
• Venous claudication (pain with exercise)
• Chronic leg swelling
• Skin changes consistent with venous insufficiency
• Venous ulceration in advanced cases

Diagnosis

MTS should be suspected in patients with:

• Recurrent left-sided DVTs without other clear risk factors
• Left lower extremity DVT in young, otherwise healthy patients
• Persistent symptoms despite adequate anticoagulation

Diagnostic imaging includes:

• Duplex ultrasound: Initial screening but limited for visualizing iliac veins
• CT venography or MR venography: Shows compression of left common iliac vein
• Contrast venography: Gold standard that demonstrates compression and collateral formation
• Intravascular ultrasound (IVUS): Provides detailed assessment of venous compression

Management

Standard anticoagulation alone is insufficient for treating MTS-related DVT 6. A more comprehensive approach is required:

1. Acute DVT management:

   • Catheter-directed thrombolysis (CDT) or pharmacomechanical catheter-directed thrombolysis (PCDT) is reasonable for patients with:
     • Limb-threatening circulatory compromise (phlegmasia cerulea dolens) 1
     • Rapid thrombus extension despite anticoagulation 1
     • Symptomatic deterioration despite anticoagulation 1

2. Addressing the underlying compression:

   • Endovascular stent placement in the compressed iliac vein segment is generally recommended after thrombolysis 1
   • Stenting has been shown to improve patency rates compared to anticoagulation alone 1

3. Anticoagulation:

   • Required after stent placement, typically for at least 6 months 6
   • May need to be extended or indefinite in cases of recurrent thrombosis

Long-term Outcomes and Complications

• Postthrombotic syndrome (PTS) occurs in a significant percentage of patients (reported as high as 62% in some pediatric cohorts) 2
• Recurrent DVT can occur even after stent placement (reported in 30% of pediatric patients) 2
• Stent migration or fracture is a rare but serious complication 5
• Without appropriate treatment, patients may develop chronic venous insufficiency

Special Considerations

• In pregnant women or those planning pregnancy, MTS requires special attention as pregnancy increases thrombotic risk
• Pediatric patients with MTS need careful monitoring as there are no standardized treatment guidelines for this population 2
• Patients with recurrent thrombosis despite standard therapy may require more aggressive anticoagulation strategies, including consideration of dual antiplatelet therapy in combination with anticoagulation in selected cases 5

Clinical Pearls

• MTS should be considered in any patient with unprovoked left lower extremity DVT, especially young females
• Systemic anticoagulation alone is insufficient treatment for MTS-related DVT
• Early intervention with thrombolysis and stenting may reduce the risk of postthrombotic syndrome
• Long-term follow-up is essential to monitor for recurrent thrombosis and stent patency