Overview
Definition:
May-Thurner syndrome (MTS), also known as the iliac vein compression syndrome, is an anatomical variant where the right common iliac artery compresses the left common iliac vein against the lumbar spine
This compression can lead to chronic venous stasis, increased risk of deep vein thrombosis (DVT) in the left leg, and chronic venous insufficiency
Iliac vein stenting is a minimally invasive endovascular procedure to relieve this obstruction.
Epidemiology:
The exact prevalence of MTS is difficult to determine due to asymptomatic cases and variability in diagnostic criteria
Autopsy studies suggest compression in 15-30% of individuals
Symptomatic MTS is less common, but it is a recognized cause of left-sided DVT, particularly in younger individuals (20-50 years old) and women, often associated with pregnancy or oral contraceptive use
It is estimated to be the underlying cause in up to 80% of left-sided iliofemoral DVTs.
Clinical Significance:
Untreated MTS can lead to significant morbidity, including chronic leg swelling, pain, skin changes (hyperpigmentation, stasis dermatitis), venous ulcers, and a substantially increased risk of recurrent DVT and pulmonary embolism
Early diagnosis and appropriate intervention, such as stenting, are crucial to restore venous outflow, alleviate symptoms, prevent post-thrombotic syndrome, and improve long-term quality of life.
Clinical Presentation
Symptoms:
Left leg swelling (edema)
Leg pain, particularly with activity (claudication)
Heaviness or aching in the left leg
Skin changes on the left leg: hyperpigmentation, induration, or venous ectasias
Varicose veins in the left leg or pelvic region
Increased risk of deep vein thrombosis (DVT) presenting as acute pain, swelling, warmth, and tenderness in the left leg.
Signs:
Unilateral edema of the left lower extremity
Dilated superficial veins on the left leg or trunk
Palpable cords of thrombosed superficial veins
Tenderness over the iliofemoral venous system
Signs of chronic venous insufficiency: stasis dermatitis, lipodermatosclerosis, or venous ulcers
Homan's sign (unreliable but may be positive in acute DVT).
Diagnostic Criteria:
There are no universally established diagnostic criteria for MTS, but a diagnosis is typically suspected in patients with unexplained left-sided iliofemoral DVT or chronic venous insufficiency
Diagnosis is confirmed by objective venous imaging demonstrating significant compression of the left common iliac vein by the right common iliac artery, particularly during venography or intravascular ultrasound (IVUS), with evidence of venous obstruction and collateral formation
A pressure gradient across the compressed segment (>2 mmHg at rest, or >5 mmHg with Valsalva or exercise) is often considered diagnostic.
Diagnostic Approach
History Taking:
Detailed history of unilateral leg swelling or pain
Onset, duration, and progression of symptoms
Associated risk factors for DVT: immobility, surgery, trauma, malignancy, hypercoagulable states, oral contraceptive use, pregnancy
Previous history of DVT or venous insufficiency
Family history of venous thromboembolic disease
Prior interventions for venous disease
Red flags: acute onset of severe pain and swelling suggesting acute DVT.
Physical Examination:
Bilateral leg circumference measurements to assess edema
Assess for pitting edema, skin texture, color, and temperature
Palpate for venous cords or tenderness
Examine for superficial venous dilation and varicosities
Assess for signs of post-thrombotic syndrome (lipodermatosclerosis, venous ulcers)..
Investigations:
Duplex ultrasonography: Initial non-invasive test to evaluate for DVT and assess venous flow and patency
May show flow disturbances at the iliac vein confluence
Computed Tomography Venography (CTV) or Magnetic Resonance Venography (MRV): Provide detailed anatomical visualization of the iliac veins and arteries, demonstrating compression and collateral formation
Intravascular Ultrasound (IVUS): Gold standard for quantifying the degree of iliac vein compression and assessing venous wall morphology
It can measure the pressure gradient across the stenosis
Conventional Venography: Historically the gold standard, performed during intervention, showing the extent of stenosis, thrombus, and collateralization.
Differential Diagnosis:
Deep vein thrombosis (DVT) of left leg due to other causes (e.g., hypercoagulable state, extrinsic compression from mass)
Pelvic tumors compressing the iliac vein
Gynecological conditions (e.g., ovarian hyperstimulation syndrome, pregnancy-related venous compression)
Retroperitoneal fibrosis
Iliac artery aneurysm
Lymphadenopathy
Superficial thrombophlebitis
Chronic venous insufficiency from other causes.
Management
Initial Management:
For acute DVT, initial management includes anticoagulation (e.g., unfractionated heparin followed by warfarin or direct oral anticoagulants (DOACs)) to prevent further clot propagation and reduce the risk of PE
For symptomatic chronic venous compression without acute DVT, initial management may involve conservative measures like compression therapy and anticoagulation if indicated for recurrent DVT risk.
Medical Management:
Anticoagulation is the mainstay for acute DVT
Warfarin (target INR 2.0-3.0) or DOACs (e.g., rivaroxaban, apixaban, dabigatran, edoxaban) are used for 3-6 months or longer, depending on risk factors and recurrence
For chronic symptoms, graded compression stockings (Class II or III) are essential
Pharmacomechanical thrombolysis may be considered in select cases of severe acute DVT with limb-threatening ischemia or massive DVT to facilitate subsequent stenting.
Surgical Management:
Endovascular intervention is the preferred treatment for symptomatic MTS
This involves iliac vein stenting
Indications include significant left iliofemoral venous obstruction causing symptoms, a pressure gradient across the stenosis (>2 mmHg at rest or >5 mmHg with maneuvers), and failure of conservative management
The procedure typically involves venography, IVUS assessment, angioplasty, and placement of a self-expanding stent (e.g., Wallstent, Viabahn) across the compressed segment
Thrombus aspiration or thrombectomy may precede stenting in cases of acute DVT
Open surgical reconstruction (e.g., Palma procedure) is rarely performed for MTS and reserved for complex cases not amenable to endovascular treatment.
Supportive Care:
Elevation of the affected limb
Graduated compression stockings
Regular ambulation and exercise to promote venous return
Skin care to prevent breakdown and manage stasis dermatitis
Patient education on lifestyle modifications and recognition of recurrent DVT symptoms.
Complications
Early Complications:
Bleeding at the access site (groin hematoma, pseudoaneurysm)
Arteriovenous fistula at the access site
Stent migration or embolization
In-stent thrombosis (acute)
Allergic reaction to contrast media
Renal injury from contrast
Femoral vein injury
Dissection of the iliac vein or artery.
Late Complications:
In-stent restenosis due to neointimal hyperplasia or chronic thrombosis
Chronic venous stenosis or occlusion
Post-thrombotic syndrome (PTS) despite successful stenting
Recurrent DVT
Chronic venous insufficiency
Pain and swelling refractory to treatment.
Prevention Strategies:
Meticulous technique during endovascular access and stent deployment
Appropriate stent selection based on venous anatomy and lesion characteristics
Aggressive anticoagulation post-stenting, especially in cases of acute DVT
Adherence to long-term anticoagulation as prescribed
Long-term use of compression stockings
Regular follow-up with duplex ultrasound to monitor stent patency and detect early signs of restenosis.
Prognosis
Factors Affecting Prognosis:
Timeliness of diagnosis and intervention
Presence and extent of acute DVT at presentation
Success of the stenting procedure (achieving good lumen gain and favorable pressure gradient)
Adherence to anticoagulation and compression therapy
Presence of underlying hypercoagulable states
Degree of pre-existing venous damage and post-thrombotic changes.
Outcomes:
With successful iliac vein stenting, most patients experience significant symptom relief, including reduced leg swelling, pain, and improved quality of life
Long-term patency rates for iliac vein stents in MTS are generally high (80-90% at 5 years), especially when treating isolated venous compression without extensive chronic DVT
Patients with pre-existing significant PTS may have less dramatic improvement but can still benefit from reduced symptom burden.
Follow Up:
Lifelong follow-up is generally recommended
Initial follow-up typically involves duplex ultrasound at 1, 3, 6, and 12 months post-procedure, then annually or as needed
Regular clinical assessment for recurrence of symptoms or signs of venous insufficiency
Emphasis on continued use of compression stockings and appropriate anticoagulation
Patients should be educated on signs of recurrent DVT and advised to seek immediate medical attention.
Key Points
Exam Focus:
MTS is defined by compression of the left common iliac vein by the right common iliac artery, leading to left-sided DVT/venous insufficiency
Imaging of choice for diagnosis: MRV/CTV, IVUS confirms and quantifies
Treatment of choice for symptomatic MTS: iliac vein stenting
Anticoagulation is critical for acute DVT and post-stenting
Complications include in-stent thrombosis/restenosis and PTS.
Clinical Pearls:
Suspect MTS in young patients with isolated left lower extremity DVT or chronic venous insufficiency
Always assess for a pressure gradient across the iliac vein confluence, especially during venography or IVUS
Consider caval filters only if there is contraindication to stenting and high risk of PE
Stent placement should ideally restore venous flow and minimize pressure gradient
Long-term compliance with anticoagulation and compression is vital for successful outcomes.
Common Mistakes:
Misdiagnosing MTS as isolated DVT without investigating the iliac vein confluence
Delaying intervention in acute iliofemoral DVT due to MTS, leading to increased PTS
Inadequate anticoagulation post-stenting, increasing risk of in-stent thrombosis
Forgetting to check for a pressure gradient, leading to undertreatment or overtreatment
Underestimating the importance of long-term compression therapy and patient adherence.