May Thurner Syndrome: Symptoms, Types, Causes and Treatment

May Thurner Syndrome (MTS), also known as iliac vein compression syndrome, is a frequently underdiagnosed vascular disorder that can lead to significant complications if left untreated. While often silent, MTS can provoke a range of symptoms, from subtle leg discomfort to life-threatening blood clots. This article will guide you through the key symptoms, types, causes, and latest treatment strategies based on up-to-date clinical evidence.

Symptoms of May Thurner Syndrome

May Thurner Syndrome often presents a diagnostic challenge due to its diverse and sometimes subtle symptomatology. While some individuals remain asymptomatic, others may experience a variety of symptoms that can mimic other vascular or musculoskeletal conditions. Recognizing these symptoms early is crucial for timely diagnosis and intervention.

Symptom	Description	Severity/Impact	Source(s)
Leg Swelling	Unilateral (usually left), persistent or acute	Ranges from mild to severe	1 2 3 4 11
Leg Pain	Aching, heaviness, or discomfort	Can limit mobility	1 2 3 5 11
Skin Changes	Discoloration, pigmentation, ulcers	Sign of chronic disease	1 2 4 11
DVT/PE	Deep vein thrombosis, pulmonary embolism	Life-threatening	3 5 7 8 10 11

Table 1: Key Symptoms

Understanding the Symptom Spectrum

Leg Swelling and Pain

• The most common symptoms are swelling and pain, typically affecting the left lower limb. This is due to impaired venous outflow caused by compression of the left common iliac vein, leading to venous congestion 1 2 3 11.
• Swelling can be persistent or triggered by prolonged standing or activity. Pain is often described as a dull ache or feeling of heaviness.

Skin Changes and Ulcers

• Chronic venous stasis can result in skin discoloration (hyperpigmentation) and, in advanced cases, stasis ulcers. These changes indicate long-standing, untreated venous hypertension 1 2 4 11.
• These findings are more often seen in patients with a delayed diagnosis.

Deep Vein Thrombosis and Pulmonary Embolism

• MTS is a major but under-recognized cause of iliofemoral deep vein thrombosis (DVT), especially in young women 3 5 7 8 10 11.
• If a clot dislodges, it can travel to the lungs, causing a pulmonary embolism (PE), which is potentially fatal.
• Notably, pulmonary embolism at presentation is more common in women with MTS 11.

Other and Atypical Presentations

• Some patients present with more unusual symptoms, such as claudication, unexplained dyspnea, or even seizures (secondary to hypoxia from massive PE) 4 5 8.

Asymptomatic Cases

• Many individuals with the anatomical variant never develop symptoms, making the true prevalence difficult to estimate 6 7 9.

Types of May Thurner Syndrome

The clinical expression of May Thurner Syndrome can vary not only by severity but also by anatomical variation and associated complications. Understanding these types can help clinicians tailor diagnostic and therapeutic strategies.

Type	Key Feature	Typical Patient Profile	Source(s)
Classic/Primary	Left iliac vein compressed by right iliac artery	Young to middle-aged women	1 2 6 7 11
Secondary	Compression by non-arterial structures (e.g., tumor, myoma)	Any age	9
Double Compression	Compression by both right and left iliac arteries	Elderly, anatomical variant	4
Asymptomatic	Anatomical variant without symptoms	All ages	6 7

Table 2: Types of May Thurner Syndrome

Exploring the Variants

Classic (Primary) May Thurner Syndrome

• The classic form involves compression of the left common iliac vein by the overlying right common iliac artery against the lumbar spine 1 2 6 7.
• Most commonly seen in young to middle-aged women, but can occur in men and older adults 11.

Secondary (Non-Classic) Forms

• Secondary MTS arises when external factors, such as tumors (e.g., large uterine myoma), post-surgical changes, or anatomical variants cause compression 9.
• These cases can occur at any age and may be more challenging to diagnose.

Double Compression

• Rarely, the left common iliac vein is compressed by both the right and left iliac arteries, sometimes exacerbated by bony structures such as osteophytes 4.
• Double stenosis can increase the severity of symptoms and complicate treatment.

Asymptomatic Anatomical Variant

• Up to 20% of the population may have the anatomical configuration without clinical symptoms 6 7.
• These individuals are typically only identified incidentally during imaging for other conditions.

Causes of May Thurner Syndrome

MTS is fundamentally a result of anatomical vascular compression, but several contributing factors and mechanisms influence its development and progression. Understanding the root causes and risk factors is vital for both prevention and early recognition.

Cause/Mechanism	Description	Risk Factors/Situations	Source(s)
Anatomical Compression	Left iliac vein compressed by right iliac artery	Congenital variant	1 2 3 6 7 8
Chronic Pulsation	Repetitive arterial pulsation damages vein wall	Aging, chronicity	5 8
Secondary Compression	Tumors, myomas, surgical changes	Gynecological tumors, surgery	9
Additional Triggers	Immobility, dehydration, pregnancy, postpartum	Surgery, trauma, multiple pregnancies	9 13

Table 3: Causes and Mechanisms

Delving into the Causes

Anatomical Compression

• The fundamental cause is the compression of the left common iliac vein by the right common iliac artery (and sometimes the spine or other arteries), leading to localized narrowing (stenosis) and turbulent blood flow 1 2 3 6 7 8.
• This anatomical variant is present in many, but not all develop symptoms.

Chronic Pulsation and Fibrous Changes

• Over time, the pulsatile movement of the artery can cause chronic irritation, leading to thickening and fibrosis of the vein wall, further narrowing the vessel and predisposing to thrombosis 5 8.

Secondary or Acquired Compression

• Tumors (especially large pelvic masses like uterine myomas), surgical scarring, or structural changes can externally compress the vein, mimicking or exacerbating classic MTS 9.
• Such cases are less common but highlight the importance of considering secondary causes, especially in older patients or those with a relevant medical history.

Triggering and Aggravating Factors

• Periods of immobilization (such as bed rest or long travel), dehydration, pregnancy, postpartum changes, and certain medical therapies can increase the risk of thrombosis in individuals with underlying MTS anatomy 9 13.
• Multiple risk factors often act together to provoke symptomatic disease.

Treatment of May Thurner Syndrome

Advances in minimally invasive vascular interventions have transformed the management of May Thurner Syndrome. Treatment must be individualized, depending on the severity of symptoms, presence of complications (like DVT), and underlying anatomical factors.

Treatment Option	Approach/Procedure	Typical Indications	Source(s)
Anticoagulation	Blood thinners to prevent/ treat clot	Initial DVT, mild cases	3 7 10 12
Thrombolysis	Catheter-directed clot dissolution	Extensive DVT, acute cases	1 2 10 12 13
Stenting/Angioplasty	Endovascular stent placement to relieve compression	Residual stenosis, chronic symptoms	1 2 10 12 13
IVC Filter	Temporary filter in vena cava to prevent PE	High clot burden, PE risk	1 2
Surgery	Open surgical correction (rare)	Refractory or complex cases	11 13

Table 4: Treatment Strategies

Modern Management Approaches

Anticoagulation

• Systemic anticoagulation (e.g., heparin, warfarin, DOACs) is essential for initial management of DVT and as adjunct to other therapies 3 7 10 12.
• However, anticoagulation alone is generally insufficient for definitive management of MTS because it doesn't address the underlying compression 7.

Catheter-Directed Thrombolysis

• For extensive or acute DVT, direct infusion of clot-dissolving medications (e.g., urokinase, tPA) via catheter has become the first-line intervention 1 2 10 12 13.
• This approach rapidly restores vein patency and reduces the risk of post-thrombotic syndrome.

Endovascular Stenting and Angioplasty

• After thrombolysis, residual narrowing is treated with balloon angioplasty and placement of a self-expanding stent in the compressed segment of the iliac vein 1 2 10 12 13.
• Stenting effectively relieves the mechanical obstruction and is associated with high technical success (up to 95%) and excellent patency rates at one year (96%) 10 12.
• Post-procedure anticoagulation is typically continued for several months or longer to prevent recurrent thrombosis.

Inferior Vena Cava (IVC) Filter

• In patients with a high risk of pulmonary embolism or contraindications to anticoagulation, a temporary IVC filter may be placed to catch emboli before they reach the lungs 1 2.

Surgical Options

• Open surgical correction is rarely required but may be considered in cases where endovascular therapy fails or is contraindicated 11 13.
• Surgical options carry higher complication rates compared to endovascular approaches 11.

Special Considerations

• In adolescents and special populations, the same endovascular strategies are applied, though long-term outcomes and potential complications of stenting require further research 13.
• Lifelong chemoprophylaxis may be necessary for patients with recurrent events or underlying thrombophilia, even after successful intervention 5.

Conclusion

May Thurner Syndrome is an under-recognized but clinically significant cause of lower limb venous disease and thrombotic complications. Early diagnosis and appropriate intervention can dramatically improve outcomes and quality of life for affected individuals.

Key Takeaways:

• Symptoms range from subtle leg swelling and pain to severe complications like DVT and pulmonary embolism.
• Types include classic, secondary (due to tumors or other compressive forces), double compression, and asymptomatic anatomical variants.
• Causes center on anatomical compression of the left iliac vein, but may be aggravated by secondary factors and lifestyle triggers.
• Treatment strategies favor minimally invasive endovascular approaches—catheter-directed thrombolysis and stenting are now the mainstay, with anticoagulation as adjunct therapy.

A high index of suspicion, especially in young women with unilateral left leg DVT, is crucial for timely diagnosis. Modern imaging and endovascular therapies offer excellent outcomes when applied early and appropriately. Ongoing research will continue to refine management for all age groups and presentations.