May-Thurner Syndrome: Diagnosis, Management, and Endovascular Treatment Options

May-Thurner Syndrome (MTS), also known as iliac vein compression syndrome or Cockett’s syndrome, represents an important but often underdiagnosed anatomical variant that can lead to significant venous complications. This condition occurs when the right common iliac artery compresses the left common iliac vein against the lumbar vertebrae, creating a mechanical obstruction to venous outflow from the left lower extremity. This comprehensive guide explores the pathophysiology, clinical presentation, diagnostic approaches, and contemporary management strategies for May-Thurner Syndrome, with particular focus on modern endovascular treatment options.

Pathophysiology and Anatomical Considerations

Anatomical Basis

May-Thurner Syndrome results from a specific anatomical relationship:

• The left common iliac vein passes behind the right common iliac artery
• At this crossing point, the vein is compressed against the fifth lumbar vertebra
• This creates a “nutcracker” effect on the vein
• The normal anatomical variant becomes pathological when significant compression occurs

Pathophysiological Consequences

The compression leads to a cascade of venous changes:

1. Mechanical obstruction: Direct physical narrowing of the venous lumen
2. Endothelial injury: Chronic pulsatile arterial compression damages the vein wall
3. Intimal hyperplasia: Development of fibrous spurs and webs within the vein
4. Flow stasis: Reduced venous outflow velocity
5. Thrombosis: Development of deep vein thrombosis (DVT) in severe cases

Prevalence and Demographics

• General population: Anatomical compression present in 22-32% of individuals
• Symptomatic disease: Develops in a much smaller subset
• Gender distribution: Female predominance (2:1 to 5:1)
• Age: Typically presents in second to fourth decades of life
• Risk factors: Pregnancy, oral contraceptive use, dehydration, prolonged immobility

Clinical Presentation and Natural History

Spectrum of Presentations

May-Thurner Syndrome can manifest across a spectrum of severity:

• Asymptomatic compression: Incidental finding on imaging
• Chronic venous insufficiency: Edema, pain, varicosities
• Acute iliofemoral DVT: Often extensive and left-sided
• Post-thrombotic syndrome: Long-term complication of untreated MTS-related DVT

Common Symptoms

When symptomatic, patients typically report:

• Unilateral left leg swelling (80-90% of symptomatic cases)
• Leg pain or heaviness (60-70%)
• Venous claudication with activity (30-40%)
• Skin changes in advanced cases (hyperpigmentation, lipodermatosclerosis)
• Varicose veins (often pelvic and vulvar in women)
• Venous ulceration (in severe chronic cases)

自然歷史

Without intervention, MTS follows a predictable course:

• Asymptomatic compression: May remain stable indefinitely
• Symptomatic non-thrombotic disease: Progressive worsening of symptoms
• Acute thrombosis: High risk of post-thrombotic syndrome if untreated
• Recurrent thrombosis: Common with anticoagulation alone (73% at 5 years)

Diagnostic Approaches

臨床評估

A high index of suspicion is crucial for diagnosis:

• 歷史: Unilateral left leg symptoms, especially in young women
• Physical examination: Asymmetric edema, varicosities, skin changes
• Risk factor assessment: Oral contraceptives, recent pregnancy, thrombophilia

影像模式

Multiple imaging options exist, each with specific advantages:

Duplex Ultrasound

• 優勢: Non-invasive, widely available
• Findings: Asymmetric flow, velocity changes, collaterals
• 限制條件: Limited visualization of iliac veins, operator-dependent
• Role: Initial screening tool, not definitive for MTS

CT Venography

• 優勢: Excellent anatomical detail, visualizes extrinsic compression
• Findings: Venous narrowing, arterial crossing, collaterals
• 限制條件: Radiation exposure, contrast requirements
• Role: Good anatomical assessment, planning for intervention

MR Venography

• 優勢: No radiation, excellent soft tissue contrast
• Findings: Venous compression, flow characteristics
• 限制條件: Cost, availability, time-consuming
• Role: Excellent for diagnosis, particularly in younger patients

Intravascular Ultrasound (IVUS)

• 優勢: Direct visualization of vein lumen, accurate sizing
• Findings: Luminal narrowing, intraluminal webs, external compression
• 限制條件: Invasive, requires venous access
• Role: Gold standard for diagnosis and intervention planning

Conventional Venography

• 優勢: Direct visualization, pressure measurements possible
• Findings: Stenosis, collaterals, filling defects
• 限制條件: Invasive, limited cross-sectional information
• Role: Often combined with therapeutic intervention

Diagnostic Criteria

No universally accepted criteria exist, but common parameters include:

• Imaging evidence of >50% compression of left common iliac vein
• Pressure gradient >2 mmHg across stenosis
• Venographic findings of collateral vessels
• IVUS measurement of >50% area reduction
• Clinical correlation with symptoms and examination

Management Approaches

Conservative Management

For asymptomatic or mildly symptomatic patients:

• Compression therapy: Graduated compression stockings (30-40 mmHg)
• Leg elevation: Regular elevation to reduce venous pressure
• Exercise: Calf muscle pump activation
• Risk factor modification: Discontinuation of oral contraceptives if appropriate
• Surveillance: Regular follow-up to monitor for progression

Medical Management

For patients with MTS-related DVT:

• Anticoagulation: Initial treatment for acute thrombosis
• Low molecular weight heparin or direct oral anticoagulants
• Duration typically extended due to anatomical risk factor
• 限制條件: Does not address underlying compression
• Recurrence risk: High with anticoagulation alone (73% at 5 years)

Endovascular Interventions

Current standard of care for symptomatic MTS:

Catheter-Directed Thrombolysis

For patients presenting with acute thrombosis:
– Purpose: Dissolve acute thrombus before addressing compression
– 技術: Infusion catheter placed throughout thrombosed segment
– 時間長度: 24-72 hours of thrombolytic infusion
– Efficacy: 80-90% successful thrombus removal
– 限制條件: Bleeding risk, contraindications in some patients

Percutaneous Transluminal Angioplasty (PTA)

• Purpose: Initial dilation of compressed segment
• 技術: High-pressure balloon inflation
• 限制條件: High recurrence rate (>70%) when used alone
• Role: Preparatory step before stenting

Venous Stenting

Current gold standard for symptomatic MTS:
– Purpose: Maintain patency of compressed vein
– 技術: Deployment of self-expanding stents across compressed segment
– Stent selection:
– Dedicated venous stents preferred (high radial force, flexibility)
– Examples: Wallstent, Vici, Venovo, Zilver Vena
– Sizing: Typically 14-18mm diameter, 40-90mm length
– Technical considerations:
– Extension into inferior vena cava often necessary
– Coverage of entire compressed segment critical
– Post-dilation to nominal diameter
– Outcomes:
– Technical success: >95%
– Primary patency: 79-100% at 1 year
– Secondary patency: 85-100% at 3 years
– Symptom improvement: 82-95%

Intravascular Ultrasound Guidance

• Purpose: Accurate diagnosis and stent sizing
• 優勢: Direct visualization of compression and results
• 技術: IVUS catheter assessment before and after intervention
• Impact: Improves technical success and long-term outcomes

Surgical Options

Reserved for endovascular failures or specific scenarios:

• Venous bypass procedures:
• Femoro-femoral crossover bypass
• Saphenopopliteal bypass

• Complex reconstructions

• Open thrombectomy with patch venoplasty:

• For acute extensive thrombosis

• Limited role in modern practice

• Arterial transposition:

• Repositioning of right common iliac artery
• Rarely performed, high morbidity

Post-Intervention Management

Anticoagulation

• Post-stenting: Typically 3-6 months of anticoagulation
• Post-thrombotic cases: Extended anticoagulation often required
• Agent selection: No consensus, options include:
• Direct oral anticoagulants
• Low molecular weight heparin
• Warfarin

Antiplatelet Therapy

• 時間長度: Lifelong in most cases
• Regimen: Single antiplatelet (aspirin 81-325mg daily)
• Dual antiplatelet: Sometimes used short-term (1-3 months)

Follow-up Protocols

• Clinical assessment: 1, 3, 6, and 12 months, then annually
• Imaging surveillance:
• Duplex ultrasound at 1, 3, 6, and 12 months
• CT or MR venography for suspected complications
• Symptom monitoring: Education regarding warning signs

併發症管理

• In-stent restenosis:
• Incidence: 5-15% at 1 year

• Management: Re-intervention with balloon angioplasty or additional stenting

• Stent migration:

• Prevention: Proper sizing and positioning

• Management: Endovascular retrieval or additional stenting

• Stent thrombosis:

• Acute management: Catheter-directed thrombolysis
• Prevention: Adequate anticoagulation, addressing inflow/outflow issues

Special Populations and Considerations

Pregnancy and May-Thurner Syndrome

• Increased risk: Pregnancy exacerbates compression
• Management challenges: Limited imaging and intervention options
• Approach: Compression therapy, careful anticoagulation
• Post-partum: Definitive intervention if symptomatic

Thrombophilia and May-Thurner Syndrome

• Compound risk: Anatomical plus biochemical hypercoagulability
• Screening: Consider in younger patients with MTS-related DVT
• Management: May require indefinite anticoagulation after intervention

Pediatric May-Thurner Syndrome

• Considerations: Growth potential, long-term stent durability
• Approach: Conservative management when possible
• Intervention: Larger stent diameters to accommodate growth

醫療免責聲明

重要通知: This information is provided for educational purposes only and does not constitute medical advice. May-Thurner Syndrome can be associated with serious vascular complications that require proper medical evaluation. The diagnostic approaches and treatment options discussed should only be implemented under the guidance of qualified healthcare professionals after appropriate assessment. Individual results may vary, and all interventions carry potential risks and benefits that should be thoroughly discussed with your healthcare provider. If you are experiencing symptoms suggestive of venous disease or May-Thurner Syndrome, please consult with a vascular specialist for personalized evaluation and treatment recommendations.

總結

May-Thurner Syndrome represents an important anatomical variant that can lead to significant venous morbidity when symptomatic. Modern diagnostic approaches, particularly cross-sectional imaging and intravascular ultrasound, have improved recognition of this condition. Contemporary management has evolved dramatically with the development of dedicated venous stents and endovascular techniques, offering excellent technical success and symptom improvement with lower morbidity than traditional surgical approaches. A high index of suspicion in appropriate populations, particularly young women with left-sided venous symptoms or DVT, is essential for timely diagnosis and intervention. With proper recognition and management, the majority of patients with symptomatic May-Thurner Syndrome can expect excellent long-term outcomes and significant improvement in quality of life.