What is the diagnosis and treatment for May-Thurner syndrome (MTS)?

May-Thurner Syndrome: Diagnosis and Treatment

May-Thurner Syndrome (MTS) requires endovascular stent placement following catheter-directed thrombolysis as the primary treatment approach, as standard anticoagulation alone is insufficient for treating MTS-related deep vein thrombosis. 1

Diagnosis of May-Thurner Syndrome

May-Thurner Syndrome is characterized by compression of the left common iliac vein by the right common iliac artery against the lumbar spine, resulting in venous outflow obstruction and commonly presenting with left-sided lower extremity deep vein thrombosis (DVT).

Diagnostic Approach:

1. Initial Imaging:

   • Ultrasound duplex Doppler of lower extremity is the recommended initial imaging examination for suspected DVT 2
   • However, ultrasound has limitations for visualizing iliac veins and may miss MTS

2. Advanced Imaging (when MTS is suspected):

   • CT Venography (CTV): Clearly identifies stenosis, occlusion, venous atresia, collaterals, and edema 2
   • MR Venography (MRV): Excellent for delineating extravascular anatomy and identifying sources of extrinsic venous compression 3
   • Catheter Venography with IVUS: Most sensitive and specific modality for deep vein obstructive disease, typically performed during intervention 2

Clinical Suspicion Indicators:

• Left-sided DVT, particularly in young and otherwise healthy patients 2
• Recurrent unprovoked DVTs of the left lower extremity despite adequate anticoagulation
• Unilateral left leg swelling, pain, or venous claudication
• Venous stasis changes or venous ulceration in advanced cases

Treatment Algorithm

1. Initial Management:

   • Anticoagulation is generally first-line therapy for acute iliofemoral DVT 2
   • However, anticoagulation alone is insufficient for MTS as recurrent VTE occurs more frequently compared to those who receive additional interventional treatment 2

2. Definitive Treatment:

   • Catheter-directed thrombolysis (CDT) or pharmacomechanical catheter-directed thrombolysis (PCDT) followed by endovascular stent placement 1
   • Indications for intervention include:
     • Limb-threatening circulatory compromise
     • Rapid thrombus extension despite anticoagulation
     • Symptomatic deterioration despite anticoagulation

3. Post-Intervention Management:

   • Anticoagulation is required after stent placement, typically for at least 6 months 1
   • May need extended or indefinite anticoagulation in cases of recurrent thrombosis
   • Regular follow-up with Doppler ultrasonography to monitor stent patency

Treatment Outcomes

• Complete symptomatic regression occurs in approximately 82.6% of patients following endovascular treatment 1
• Endovascular stenting shows 90-96% patency rates at 1-year follow-up 1
• Early intervention is critical to prevent post-thrombotic syndrome and chronic venous hypertension 1

Special Considerations

• While MTS typically affects the left iliac vein, rare cases of right-sided MTS have been reported in patients with anatomical variations like left-sided inferior vena cava 4
• MTS should be considered in all patients with left-sided DVT, especially young females, though it can occur in males as well 1
• Endovascular treatment has largely replaced open surgical approaches due to lower morbidity and good technical success rates 1

Pitfalls to Avoid

• Failure to suspect MTS in young patients with left-sided DVT
• Relying solely on ultrasound for diagnosis, which may miss iliac vein compression
• Using anticoagulation alone without addressing the mechanical compression
• Inadequate follow-up after stent placement, which can lead to undetected stent thrombosis

Early recognition and appropriate intervention are essential to prevent long-term complications of MTS, including post-thrombotic syndrome, chronic venous insufficiency, and recurrent DVT.