01Approach to the Critical Patient/attcp39

Immediate Threats

›Life-threatening presentations requiring emergent action

›Pulmonary embolism from iliofemoral DVT

›Acute dyspnea, tachycardia, pleuritic chest pain, new hypoxia

›Activate PE response team; initiate CTPA without delay

›If massive PE with hemodynamic instability, consider systemic thrombolysis

›Phlegmasia cerulea dolens

›Tense limb swelling with cyanosis and impending venous gangrene

›Emergent vascular surgery and interventional radiology consultation

›Therapeutic anticoagulation immediately; prepare for catheter-directed intervention

›Hemodynamic instability

›SBP < 90 mmHg or MAP < 65 mmHg

›IV access x2, fluid resuscitation, cardiac monitoring

Stabilization Priorities

›Initial resuscitation targets

›Oxygen supplementation for SpO2 < 94%

›High-flow oxygen via non-rebreather mask if SpO2 < 90%

›Intubation if respiratory failure or altered mental status

›IV access and hemodynamic monitoring

›Two large-bore peripheral IVs

›Continuous cardiac monitoring and pulse oximetry

›Anticoagulation initiation for confirmed or high-suspicion DVT/PE

›LMWH or unfractionated heparin before definitive imaging in high-probability cases

›Hold anticoagulation if active bleeding or contraindication present

Consultation Triggers

›Mandatory early consultation

›Vascular surgery or interventional radiology for all confirmed MTS with DVT

›Catheter-directed thrombolysis or mechanical thrombectomy planning

02History/hx47

Presenting Symptoms

›Cardinal symptom: left lower extremity swelling

›Present in approximately 70% of MTS patients

›Often painless initially; asymmetric left greater than right

›Acute onset over days suggests DVT; chronic or progressive suggests venous stasis

›Associated limb symptoms

›Dull aching or heaviness in the left leg

›Venous claudication with ambulation

›Skin discoloration, paresthesias, or ulceration in chronic cases

›Systemic alarm symptoms

›Acute dyspnea, pleuritic chest pain, hemoptysis (PE concern)

›Palpitations or presyncope with tachycardia

Temporal and Contextual Factors

›Onset triggers and timing

›Peripartum period or recent pregnancy

›Initiation of oral contraceptives (mean onset approximately 5 weeks after starting OCPs)

›Postoperative state or prolonged immobilization

›Recent long-haul travel (>4 hours)

›Symptom progression

›Rapid progression despite anticoagulation suggests underlying anatomical obstruction

›Median time from DVT to MTS diagnosis was 0.65 months in adolescent series

Risk Factors

›Patient-specific risk profile

›Female sex: 78% of MTS patients in RIETE registry were female

›Mean age 42 years in MTS vs 62 years in non-MTS DVT

›Estrogen exposure

›Oral contraceptives, hormone replacement therapy, tamoxifen

›Pregnancy and peripartum period

03Physical Exam/exam26

Vital Signs

›Hemodynamic and respiratory assessment

›Tachycardia: heart rate > 100 bpm suggests PE or significant DVT burden

›Hypoxia: SpO2 < 94% on room air warrants immediate evaluation for PE

›Tachypnea and hypotension: PE or phlegmasia cerulea dolens

›Fever: consider secondary infection or phlebitis

Lower Extremity Examination

›Limb assessment

›Unilateral or asymmetric edema: left greater than right is the hallmark finding

›Bilateral calf and thigh circumference measurement

›Greater than 2 cm difference is clinically significant

›Pitting edema, calf tenderness

›Homan's sign: low sensitivity and specificity; not reliable alone

›Skin changes in chronic cases

›Hyperpigmentation, induration, venous ectasia

›Stasis dermatitis and venous ulceration

›Phlegmasia cerulea dolens findings (surgical emergency)

›Tense swelling with cyanotic discoloration

›Diminished distal pulses

›Impending venous gangrene

Cardiopulmonary Examination

›Cardiopulmonary findings suggesting PE

›Tachycardia and diminished breath sounds

›Pleuritic rub on auscultation

›Signs of right heart strain: elevated JVP, right ventricular heave

Abdominal and Pelvic Examination

›Ancillary exam findings

›Pelvic collateral veins visible on abdominal wall in chronic obstruction

04Differential Diagnosis/ddx44

Vascular Causes

›DVT without iliac vein compression

›ICD-10: I80.209 (unspecified DVT of lower extremity)

›Most common mimic; distinguished by advanced imaging showing absence of iliac vein compression

›Both provoked (surgery, immobility) and unprovoked subtypes

›May-Thurner Syndrome (Cockett Syndrome)

›ICD-10: Q27.8 (other specified congenital anomalies of peripheral vascular system)

›Left common iliac vein compression between right common iliac artery and L5 vertebral body

›Accounts for 2-5% of all DVTs; likely underdiagnosed

›IVC anomalies

›IVC agenesis or duplication causing venous stasis

›Bilateral or right-sided DVT pattern; CT venography distinguishes

Infectious and Inflammatory

›Cellulitis

›ICD-10: L03.119 (cellulitis of lower limb)

›Erythema, warmth, fever; discrete margins; no venous obstruction on imaging

›Can coexist with DVT; both diagnoses may require treatment

›Septic thrombophlebitis

›ICD-10: I80.8 (phlebitis and thrombophlebitis of other sites)

›Fever, bacteremia, inflammatory markers elevated; IV antibiotics required

Mechanical and Structural

›Extrinsic iliac vein compression

›ICD-10: I87.1 (compression of vein)

›Pelvic mass, lymphadenopathy, retroperitoneal fibrosis; CT/MRI distinguishes

›Lymphoma, gynecologic malignancy, retroperitoneal fibrosis as causes

›Baker's cyst rupture

›ICD-10: M71.20 (synovial cyst of popliteal space)

›Posterior knee pain, popliteal fullness; ultrasound diagnostic

05Laboratory Tests/lt32

Essential Blood Work

›D-dimer

›Sensitive but nonspecific for DVT; useful to rule out in low-probability patients

›Age-adjusted cutoff: age x 10 mcg/L for patients > 50 years

›Elevated in DVT, PE, malignancy, infection, pregnancy; interpret with clinical probability

›Complete blood count

›Baseline before anticoagulation initiation

›Leukocytosis suggests secondary infection; thrombocytopenia affects anticoagulation choice

›Coagulation studies

›PT/INR and aPTT: baseline before anticoagulation; INR for warfarin monitoring

›Anti-Xa level if LMWH monitoring required (renal insufficiency, pregnancy, extremes of weight)

›Comprehensive metabolic panel

›Renal function (creatinine, eGFR): determines DOAC safety and contrast suitability

›Liver function: assesses hepatic causes of edema and DOAC metabolism

›Albumin: low levels suggest systemic edema causes

Thrombophilia Workup

›Hereditary thrombophilia panel (in selected patients)

›Indications: young patients (<50 years), recurrent DVT, family history, unprovoked DVT

›Factor V Leiden mutation (PCR-based; not affected by anticoagulation)

›Prothrombin gene mutation G20210A

›Protein C activity level: reduced on warfarin; check before starting or at least 2 weeks after stopping

›Protein S antigen: reduced in pregnancy and on estrogen; check appropriately

›Antithrombin III activity: reduced by heparin; check before initiation

›Antiphospholipid antibody panel

›Lupus anticoagulant: interpret cautiously on anticoagulation

›Anticardiolipin IgG and IgM

›Anti-beta-2 glycoprotein I IgG and IgM

›Repeat positive results at 12 weeks to confirm diagnosis

06Diagnostic Tests/dt80

Scoring Systems

›DVT pre-test probability assessment

›Wells DVT Score

›Score 0 or less: low probability (DVT prevalence approximately 5%)

›Score 1-2: moderate probability (DVT prevalence approximately 17%)

›Score 3 or more: high probability (DVT prevalence approximately 53%)

›If low probability and D-dimer negative, DVT effectively excluded

›Villalta Score for post-thrombotic syndrome

›0-4: no PTS

›5-9: mild PTS

›10-14: moderate PTS

›15 or greater, or ulcer present: severe PTS

›CEAP Classification for chronic venous disease

›C0: no visible venous disease

›C1-C2: telangiectasias, varicose veins

›C3: edema

›C4: skin changes

›C5-C6: healed or active venous ulcer

›Venous Clinical Severity Score (VCSS)

›Validated for assessing clinical change in chronic venous disease

›Ten items scored 0-3 each; maximum score 30

›Pressure gradient measurement

›Gradient greater than 2 mmHg across iliac vein compression is hemodynamically significant

MRI

›MR venography (MRV)

›Indications

›Alternative to CT venography in patients with renal insufficiency or contrast allergy

›Superior anatomical resolution above the inguinal ligament

›Pregnancy (avoids ionizing radiation)

›Technique

›Non-contrast 3D TSE (turbo spin echo) sequences available for renal impairment

›Contrast-enhanced MRV with gadolinium when renal function permits

›Assess left common iliac vein caliber and compression degree

›Performance

›High sensitivity for iliac vein stenosis and thrombus characterization

›Differentiates acute versus chronic thrombus

›Can identify coexisting pelvic pathology (masses, pelvic venous congestion)

›Limitations

›Longer acquisition time; limited availability acutely

›Motion artifact; may miss distal DVT compared to CTV

›Gadolinium contraindicated with eGFR < 30 mL/min/1.73m2

CT

›CT venography (CTV)

›Recommended modality for diagnosing May-Thurner Syndrome

›Sensitivity 96%, specificity 95% for iliac vein obstruction

›Clearly demonstrates left common iliac vein compression by right common iliac artery

›Identifies extent of DVT, collateral venous pathways, and anatomical variants

›Technique

›Venous phase acquisition 70-90 seconds after contrast injection

›Direct multidetector CTV: superior accuracy for iliac vein obstruction

›Assess compression ratio: greater than 50% luminal reduction is significant

›CT pulmonary angiography (CTPA)

›Indicated when PE is clinically suspected

›Combined CTV and CTPA provides comprehensive venous and pulmonary assessment

›Sensitivity approximately 83%, specificity 96% for PE

›Limitations

›Ionizing radiation; avoid in pregnancy if possible

›Iodinated contrast: renal function assessment required (eGFR > 30 mL/min/1.73m2)

›CTV less sensitive than IVUS for hemodynamic significance of stenosis

Ultrasound

›Venous duplex ultrasound (VDUS)

›Role and performance

›First-line investigation for suspected DVT

›High sensitivity (>94%) and specificity (>97%) for infrainguinal DVT

›Limited sensitivity for iliac vein pathology; poor visualization above inguinal ligament

›Indirect signs of proximal obstruction

›Loss of respiratory phasicity in femoral vein

›Attenuated flow velocities or absent augmentation

›Absence of normal cardiac pulsatility in common femoral vein

›Compression ultrasound technique

›Noncompressibility of vein lumen: primary diagnostic criterion for DVT

›Assess common femoral, femoral, popliteal, and trifurcation veins

›Intravascular ultrasound (IVUS)

›Most sensitive and specific modality for detecting and quantifying iliac vein stenosis

›Superior to venography alone for stent sizing and treatment planning

›Recommended when invasive venography is performed

›Identifies intrinsic defects (intimal spurs, webs) missed by external imaging

›ECG

›Obtain if PE is suspected

›Sinus tachycardia: most common finding in PE

›S1Q3T3 pattern: right heart strain; low sensitivity (approximately 20%) but specific

›Right bundle branch block or right axis deviation

›T-wave inversions in V1-V4: right ventricular strain pattern

›New atrial fibrillation may precipitate from PE

07Disposition/dispo30

Admission Criteria

›Indications for hospital admission

›Acute iliofemoral DVT requiring catheter-directed intervention

›ICU or step-down for post-procedural monitoring

›Hemodynamic instability or concurrent PE

›ICU-level care for massive or submassive PE

›Phlegmasia cerulea dolens (surgical emergency)

›Emergent interventional radiology or vascular surgery suite

›Need for IVC filter placement before intervention

›Active bleeding or contraindication to anticoagulation requiring monitoring

Observation and Inpatient Management

›Monitoring requirements for inpatient admission

›Telemetry for concurrent PE or hemodynamic compromise

›Serial limb circumference measurements to assess response

›Anticoagulation level monitoring (anti-Xa levels for LMWH)

›Stable DVT with planned next-day IR consultation: observation appropriate

Transfer Criteria

›Criteria for transfer to higher level of care

›Endovascular intervention not available at receiving facility

›Transfer to center with interventional radiology and vascular surgery capabilities

›Massive PE requiring advanced therapies (catheter-directed thrombolysis, ECMO)

›Phlegmasia cerulea dolens requiring emergent surgical thrombectomy

Discharge Criteria

›Criteria permitting safe discharge

›Clinically stable on therapeutic oral anticoagulation

›No evidence of PE or hemodynamic compromise

›Post-stent patients: patent stent confirmed, symptoms improving, anticoagulation plan in place

›Outpatient vascular surgery or IR follow-up within 1-2 weeks arranged

08Treatment/t76

Anticoagulation

›Initial anticoagulation for acute DVT or PE

›Low molecular weight heparin (LMWH)

›Enoxaparin 1 mg/kg subcutaneous every 12 hours

›Adjust to anti-Xa level 0.6-1.0 IU/mL (4 hours post-dose, twice-daily dosing)

›Renal dose adjustment: 1 mg/kg once daily if eGFR < 30 mL/min/1.73m2

›Dalteparin 200 IU/kg subcutaneous once daily (maximum 18,000 IU/day)

›Unfractionated heparin (UFH) for severe renal impairment or pre-intervention

›80 units/kg IV bolus, then 18 units/kg/hour continuous infusion

›Titrate to aPTT 60-100 seconds (1.5-2.5 x control)

›Use weight-based nomogram; reassess every 6 hours until therapeutic

›Preferred pre-catheter-directed intervention due to reversibility

›Direct oral anticoagulants (DOACs) for maintenance therapy

›Rivaroxaban 15 mg orally twice daily with food x 21 days, then 20 mg once daily

›Avoid if eGFR < 30 mL/min/1.73m2; Class I recommendation for unprovoked DVT

›Apixaban 10 mg orally twice daily x 7 days, then 5 mg twice daily

›Preferred in patients with renal impairment (eGFR 15-29 mL/min/1.73m2)

›Warfarin target INR 2.0-3.0; requires bridging with LMWH or UFH until INR therapeutic for 2 consecutive days

›Anticoagulation duration

›Minimum 6-12 months for MTS-associated DVT

›Lifelong anticoagulation recommended after multiple DVTs or persistent MTS obstruction

›Post-stent: anticoagulation preferred for 6-12 months minimum

Endovascular Intervention

›Catheter-directed thrombolysis (CDT)

›Indication: acute iliofemoral DVT with low bleeding risk and symptom onset < 14 days

›ACR Appropriateness Criteria: usually appropriate for iliofemoral DVT treatment

›Access: posterior tibial vein or popliteal vein approach

›Alteplase infusion protocol

›0.5-1 mg/hour via multi-sidehole catheter positioned within thrombus

›Maximum total dose: 40 mg per course

›Duration: typically 12-24 hours with venographic reassessment

›Concurrent UFH 500 units/hour to maintain catheter patency

›Monitor fibrinogen every 6-8 hours; stop if fibrinogen < 1.5 g/L

›Pharmacomechanical thrombectomy (PCDT)

›AngioJet mechanical thrombectomy combined with iliac vein stenting (one-stop approach)

›Superior outcomes vs traditional CDT alone

›81.5% 6-month patency vs 32% with traditional CDT

›PTS incidence 11% vs 76% with CDT alone

›Iliac vein balloon angioplasty and stenting

›Preferred definitive treatment for MTS anatomical compression

›Balloon angioplasty to fracture the intimal spur and dilate the stenosis

›Self-expanding venous stents (Wallstent, Venovo, Zilver Vena) preferred

›Stent sizing by IVUS: diameter 14-18 mm; length to cover entire lesion

›Primary patency rates: 84-94% at 12 months in adolescent/young adult series

›IVUS guidance recommended for optimal stent sizing and placement

›Non-thrombotic MTS (symptomatic compression without DVT)

›Stenting indicated for symptomatic patients with greater than 50% stenosis on imaging

›Compression gradient greater than 2 mmHg across stenosis supports intervention

›IVC filter placement

›Indications

›Anticoagulation contraindicated (active bleeding, high-risk surgery)

›Recurrent PE despite therapeutic anticoagulation

›Large thrombus burden prior to catheter-directed intervention

›Retrievable filters preferred; removal at approximately 4 weeks post-placement

Post-Procedural Antithrombotic Therapy

›Post-stent anticoagulation and antiplatelet regimen

›Anticoagulation: LMWH preferred for first 2-6 weeks post-stent

›Transition to DOAC or warfarin for minimum 6-12 months

›Lifelong anticoagulation in patients with multiple DVTs or persistent risk factors

›Antiplatelet therapy

›Associated with improved stent patency; use in addition to anticoagulation

›Aspirin 81-100 mg daily commonly added post-stenting

›Duration: typically 3-6 months post-stent

Conservative Management

›Non-thrombotic MTS or adjunct therapy

›Compression therapy

›Graduated compression stockings 30-40 mmHg for PTS prevention and symptom relief

›Pneumatic compression devices for acute hospitalized patients

›Leg elevation above heart level for acute swelling

›Discontinue estrogen-containing contraceptives; arrange alternative contraception

›Ambulation encouraged as soon as tolerated

PE Treatment (Concurrent)

›PE management in MTS context

›Massive PE (hemodynamic instability)

›Systemic alteplase 100 mg IV over 2 hours (if no contraindications)

›Contraindications: prior hemorrhagic stroke, recent surgery, active bleeding

›Catheter-directed thrombolysis as alternative if systemic lysis contraindicated

›Submassive PE (right ventricular strain, hemodynamically stable)

›Therapeutic anticoagulation; consider catheter-directed therapy

›Echocardiogram and troponin guide risk stratification

›Low-risk PE: therapeutic anticoagulation; DOAC preferred

09Special Populations/sp53

Pregnancy

›MTS in pregnancy: unique considerations

›Epidemiology and risk

›Pregnancy is a major precipitant of MTS: hypercoagulable state plus anatomical compression

›Peripartum period highest risk; iliac vein compression worsens with gravid uterus

›Recurrent pregnancy loss may be associated with antiphospholipid syndrome

›Imaging in pregnancy

›Venous duplex ultrasound is first-line (no radiation)

›MRV without gadolinium preferred if iliac vein assessment needed (avoid CT if possible)

›CT venography used only if MRV unavailable and clinical urgency warrants

›Anticoagulation in pregnancy

›LMWH is the anticoagulant of choice throughout pregnancy (Class I recommendation)

›Enoxaparin 1 mg/kg subcutaneous every 12 hours; titrate anti-Xa to 0.6-1.0 IU/mL

›DOACs are contraindicated in pregnancy (teratogenic)

›Warfarin contraindicated in first trimester and near delivery

›Continue LMWH for minimum 6 weeks postpartum and at least 3 months total

›Endovascular intervention in pregnancy

›Iliac vein stenting generally deferred to postpartum if clinically feasible

›If phlegmasia cerulea dolens or massive DVT: multidisciplinary decision; CDT may be considered with shielding

Geriatric

›MTS in elderly patients: modified approach

›Epidemiology and risk

›MTS is less common in elderly vs young adults (mean age 42 years for MTS)

›Consider alternative causes of iliac vein obstruction: malignancy, retroperitoneal fibrosis

›Higher baseline bleeding risk affects anticoagulation and intervention decisions

›Anticoagulation considerations

›Renal function decline: check eGFR before DOAC selection

›Apixaban preferred in moderate renal impairment (eGFR 15-29 mL/min/1.73m2)

10Background/b56

Epidemiology

›Prevalence and demographics

›MTS accounts for 2-5% of all lower extremity DVTs

›Likely underdiagnosed due to non-specific presentation and limited iliac vein visualization on routine ultrasound

›Asymptomatic iliac vein compression present in approximately 22% of cadaveric studies

›Female predominance: 78% of MTS patients in RIETE registry (Varona 2025)

›Mean age 42 years vs 62 years in non-MTS DVT patients

›Estrogen-exposed young women at highest risk

›OCP use: DVT onset approximately 5 weeks after initiation (Murphy 2009)

›Peripartum period represents peak risk window

›RIETE registry findings

›MTS independently predicts recurrent DVT: aHR 2.26 (95% CI 1.02-5.01)

›Despite aggressive anticoagulation and endovascular therapy

›Chronic thromboembolic pulmonary hypertension (CTEPH) association

›MTS anatomy disproportionately identified in CTEPH patients (Al-Otaibi 2021)

Pathophysiology

›Anatomical basis of MTS

›Compression mechanism

›Left common iliac vein compressed between overlying right common iliac artery and L5 vertebral body

›Pulsatile arterial compression causes intimal injury and reactive intimal hyperplasia

›Results in venous spur (Cockett spur) formation: intraluminal adhesion at compression site

›Hemodynamic consequences

›Venous outflow obstruction from the left lower extremity

›Elevated left iliac vein pressure promotes venous stasis

›Virchow's triad activation: stasis + endothelial injury + hypercoagulable state

›Thrombosis cascade

›Intimal hyperplasia and spur create nidus for thrombus formation

›Compounding hypercoagulable states (OCP, pregnancy, thrombophilia) lower threshold for DVT

›Thrombus propagates distally into femoral and popliteal veins

›Chronic changes

›Recurrent DVT leads to post-thrombotic syndrome via valvular incompetence

›Persistent venous hypertension causes skin changes, ulceration, and pain

›Collateral venous channels develop around obstruction (pelvic, retroperitoneal)

›Anatomical variants

›Right-sided compression (right iliac vein compressed by right internal iliac artery): rare

›Atypical compression sites reported at L4 level or with accessory arteries

Therapeutic Considerations

›Anticoagulation versus endovascular therapy

›Anticoagulation alone is often insufficient

›Mechanical compression persists; high recurrence risk without anatomical correction

›aHR for recurrent DVT 2.26 despite anticoagulation in MTS (RIETE registry)

›Endovascular intervention evidence

›One-stop mechanical thrombectomy plus stenting: 81.5% vs 32% 6-month patency (Shao 2026)

›PTS incidence 11% vs 76% with CDT alone in one-stop procedure cohort

›ACR Appropriateness Criteria: CDT usually appropriate for symptomatic iliofemoral DVT

›SIR Position Statement: endovascular stenting recommended for chronic iliofemoral obstruction (Vedantham 2023)

›Post-thrombotic syndrome prevention

›Graduated compression stockings reduce PTS risk after DVT

›AHA Scientific Statement (Li 2025): open vein hypothesis supports early thrombus removal

›ATTRACT trial: pharmacomechanical CDT did not reduce overall PTS but reduced severe PTS

›Endovascular therapy for established PTS

›NEJM RCT (Vedantham 2026): endovascular therapy for PTS under active study

›Stent patency associated with improved PTS scores and quality of life

›DOAC vs warfarin for long-term anticoagulation

›DOACs preferred for convenience, predictable pharmacokinetics, fewer drug interactions

›Warfarin preferred in antiphospholipid syndrome, significant renal impairment, or valvular disease

›Antiplatelet therapy for stent patency

›Antiplatelet agents associated with improved venous stent patency

›Aspirin 81-100 mg daily added post-stenting in most protocols

11Patient Discharge Instructions/pdi28

copy discharge instructions

›Discharge instructions for May-Thurner Syndrome

›What is May-Thurner Syndrome

›A vein in your pelvis called the left common iliac vein is squeezed between an artery and your spine

›This compression slows blood flow and can cause blood clots in your left leg

›You will need blood thinners and possibly a procedure to fix the compressed vein

›Your medications

›Take your blood thinner exactly as prescribed; do not skip doses

›If on warfarin (Coumadin): follow-up for INR blood test as directed; target INR 2.0-3.0

›If on rivaroxaban (Xarelto) or apixaban (Eliquis): take with food; do not stop without doctor's advice

›Do not take aspirin, ibuprofen, or naproxen unless your doctor approves while on blood thinners

›Activity and lifestyle

›Walk regularly; avoid prolonged sitting or lying still (especially on flights or long car trips)

›Elevate your left leg when resting to reduce swelling

›Wear your compression stocking as prescribed (put on in the morning before getting up)

›Avoid hot tubs, saunas, or extreme heat which can worsen swelling

›Contraceptive and hormonal advice

›Stop taking estrogen-containing birth control pills immediately; speak to your doctor about alternatives

›Do not use hormone replacement therapy without discussing with your vascular specialist

›Follow-up appointments

›Return to your vascular surgeon or interventional radiologist within 1-2 weeks

›Duplex ultrasound surveillance of your stent at 1, 3, 6, and 12 months if a stent was placed

›IVC filter removal appointment at approximately 4 weeks if a filter was placed

›Return to the emergency department immediately for

›Worsening leg swelling, pain, or skin turning blue or purple

›Shortness of breath, chest pain, or coughing up blood (possible blood clot in the lung)

›Leg becomes cold, numb, or loses sensation

›Unusual bleeding: blood in urine or stool, vomiting blood, or uncontrolled bleeding from cuts

12References/r31

Guidelines and Key Sources

›Primary references

›Chopard R, Albertsen IE, Piazza G. Diagnosis and Treatment of Lower Extremity Venous Thromboembolism: A Review. JAMA. 2020

›Comprehensive review of DVT diagnosis and treatment; foundational evidence

›Mousa AY, AbuRahma AF. May-Thurner Syndrome: Update and Review. Annals of Vascular Surgery. 2013. PMID 23850314

›Epidemiology: approximately 22% cadaveric prevalence; 2-5% of DVTs attributed to MTS

›Varona JF, et al. Clinical Characteristics and Impact of May-Thurner Syndrome in Patients With Proximal DVT: RIETE Registry. Angiology. 2025. PMID 41263573

›78% female; mean age 42 years; aHR 2.26 for recurrent DVT

›Murphy EH, et al. Symptomatic Iliofemoral DVT After OCP Use in Women With May-Thurner Syndrome. J Vasc Surg. 2009. PMID 19135831

›Mean 5 weeks from OCP initiation to DVT onset

›Cohen CT, et al. Diagnosis and Treatment of Adolescent May-Thurner Syndrome DVT. J Pediatr Hematol Oncol. 2021. PMID 33093351

›Adolescent-specific data; 0.65 months median delay to diagnosis

›Bertino FJ, et al. Iliac Vein Stent Placement in Adolescents and Young Adults With May-Thurner Syndrome. Cardiovasc Intervent Radiol. 2023. PMID 38097769

›84-94% primary patency at 12 months in adolescent/young adult cohort

›Shao T, et al. One-Stop AngioJet Mechanical Thrombectomy Combined With Iliac Vein Stenting in MTS. Medicine. 2026. PMID 41995556

›81.5% vs 32% 6-month patency; PTS 11% vs 76%

›Vedantham S, et al. SIR Position Statement on Endovascular Stenting for Chronic Iliofemoral Venous Obstruction. JVIR. 2023

›Supports stenting for symptomatic chronic iliofemoral obstruction

›Li W, Vedantham S, et al. AHA Scientific Statement: Revisiting the Open Vein Hypothesis. Circulation. 2025

›Updated evidence supporting early thrombus removal to prevent PTS

›Vedantham S, Kahn SR, Marston WA, et al. Endovascular Therapy for Post-Thrombotic Syndrome. NEJM. 2026

›RCT evaluating endovascular therapy for established PTS

›ACR Appropriateness Criteria: Radiologic Management of Iliofemoral Venous Thrombosis. JACR. 2020

›CDT usually appropriate for symptomatic iliofemoral DVT

›ACR Appropriateness Criteria: Lower Extremity Chronic Venous Disease. JACR. 2023

›Guidance on imaging approach for chronic venous disease including MTS

›Harbin MM, Lutsey PL. May-Thurner Syndrome: History of Understanding and Need for Defining Population Prevalence. J Thromb Haemost. 2020. PMID 31821707

›Population prevalence challenges; importance of advanced imaging

Evidence & Review

Evidence & Review