01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Iliofemoral DVT obstructs iliac and common femoral outflow and is usually more symptomatic than femoropopliteal or calf disease. The entire leg may swell, pain can involve groin, pelvis or back and superficial collaterals become prominent. Pelvic extension can escape routine compression imaging, so CT or MR venography may be needed when it changes intervention.
Phlegmasia alba causes severe pale swelling. Cerulea occurs when thrombus blocks deep, superficial and collateral drainage, creating massive venous hypertension, cyanosis, capillary failure, arterial inflow compromise, compartment syndrome, shock and venous gangrene. Resuscitation, elevation, anticoagulation and vascular source control proceed together.
Most iliofemoral DVT is anticoagulated. Early clot removal may reduce severe post-thrombotic morbidity but adds bleeding and procedural harm. NICE provides four selection criteria, while ESVS confines intervention to selected recent symptomatic iliofemoral clot with likely technical success and low bleeding risk. Intervention does not erase the standard anticoagulant requirement.
Key points
- A blue, massively swollen, severely painful leg with sensory or motor loss or shock is phlegmasia until proved otherwise: resuscitate and obtain immediate vascular review.
- Initial management is prompt weight-adjusted UFH or LMWH, aggressive elevation and fluid resuscitation, with urgent assessment for thrombus removal and fasciotomy if compartment syndrome develops.
- For stable symptomatic iliofemoral DVT consider catheter-directed thrombolysis only when symptoms are under 14 days, function is good, life expectancy is at least 1 year and bleeding risk is low.
- Iliofemoral DVT causes whole-leg swelling, groin or back pain and collaterals; routine proximal ultrasound may not fully map pelvic extension.
- Early thrombus removal is selective, increases major bleeding and is not recommended for disease confined to femoral, popliteal or calf veins.
- Anticoagulation remains essential after removal or iliac stenting and lasts at least as long as treatment without intervention; no universal post-stent regimen is proven.
- Pregnancy-associated iliac DVT needs urgent obstetric, vascular and haematology input rather than a generic Wells, D-dimer or DOAC pathway.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Stasis and injury
Surgery, trauma, immobility, compression or previous thrombosis promotes stasis and endothelial activation within central venous outflow.
Hypercoagulability
Active cancer, pregnancy, oestrogen exposure, inflammation and severe thrombophilia can generate extensive central clot and increase recurrence risk after the acute event.
Anatomical compression
Left iliac compression or a pelvic mass can narrow central venous drainage, producing local stasis and encouraging unilateral iliofemoral thrombosis.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Central obstruction
Occlusion of the iliac and common femoral veins blocks central drainage, sharply raising distal venous pressure and producing painful whole-limb oedema.
- 2Collateral failure
Rapid extension through deep, superficial and collateral venous channels removes compensatory outflow and creates the profound cyanotic congestion of phlegmasia cerulea.
- 3Microcirculatory collapse
Rising interstitial pressure reduces capillary perfusion, compresses small vessels and can eventually impair arterial inflow, threatening nerves, muscle and skin viability.
- 4Valve injury
Residual thrombus, inflammatory vein-wall remodelling and sustained venous hypertension damage valve function, leaving chronic obstruction, reflux and post-thrombotic morbidity.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Whole-leg swelling from groin distally, groin or back pain and superficial collaterals suggests central outflow obstruction.
A very painful pale swollen limb reflects extensive major deep-vein thrombosis before cyanotic failure.
Sudden ischaemic pain, cyanosis, functional loss, tachycardia or shock indicates near-total venous obstruction.
Sensory loss, weakness, tense compartments and diminished arterial signals indicate compromised tissue perfusion.
Dyspnoea, chest pain, haemoptysis, syncope or hypotension requires urgent PE assessment.
Recent symptoms, preserved function, one-year survival and low bleeding support intervention consideration.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Urgent duplex ultrasoundFirst step - Why
- Confirm proximal thrombosis and accessible anatomical extent.
- Interpretation and limitations
- Common femoral non-compressibility supports proximal disease; incomplete iliac views require central imaging when useful.
- 02
CT venography - Why
- Map iliac, caval and pelvic obstruction rapidly.
- Interpretation and limitations
- It defines extent and compression but uses iodine and radiation and must not delay phlegmasia treatment.
- 03
MR venography - Why
- Assess pelvic veins without ionising radiation.
- Interpretation and limitations
- Useful when timely and ultrasound is inconclusive, but availability can make it unsuitable in instability.
- 04
Arterial Doppler and compartments - Why
- Detect secondary arterial inflow failure and compartment syndrome.
- Interpretation and limitations
- Weak signals, neurological loss or tense painful compartments demand immediate surgical assessment.
- 05
Baseline bloods and crossmatch - Why
- Prepare for anticoagulation, lysis or urgent intervention.
- Interpretation and limitations
- FBC, renal and liver function, PT, APTT, fibrinogen and crossmatch identify bleeding and organ modifiers.
- 06
Thrombolysis contraindications - Why
- Determine whether lytic exposure is acceptably safe.
- Interpretation and limitations
- Active bleeding, recent intracranial disease, major surgery or uncontrolled hypertension may favour other rescue methods.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Acute limb ischaemia
Arterial embolism causes pallor and pulseless neurological loss with less early oedema, although phlegmasia can reduce signals.
Necrotising infection
Toxicity, disproportionate pain, gas or rapid skin destruction may mimic phlegmasia and needs surgical source control.
Compartment syndrome
Tense compartments and passive-stretch pain may complicate DVT or follow trauma and require immediate surgical review.
Cellulitis or lymphoedema
Cellulitis causes inflammatory erythema and systemic features, while lymphoedema causes chronic tissue swelling; neither usually produces abrupt cyanotic whole-limb venous congestion.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked case: phlegmasiaRescue threatened limbFirst stepAn adult has cyanosis, tense swelling, sensory loss and hypotension with extensive iliofemoral thrombosis.+
- 1Begin ABC resuscitation, obtain large-bore access, bloods and crossmatch and summon vascular, interventional and anaesthetic teams.
- 2Elevate the limb, replace intravascular volume and give weight-adjusted heparin unless a contraindication requires another senior plan.
- 3Use duplex and central imaging only when it supports rescue, while repeatedly checking arterial signals, neurology and compartments.
- 4If repeated examination confirms compartment syndrome, perform immediate fasciotomy; when indicated, surgical decompression may precede thrombus removal rather than waiting for venous clearance to finish.
- 5Select catheter-directed thrombolysis, pharmacomechanical treatment or surgical thrombectomy according to anatomy, bleeding risk and available expertise; address iliac obstruction when indicated, continue standard-duration anticoagulation and verify perfusion, renal function and bleeding.
02Stable intervention pathwayApply four criteriaA stable patient has symptomatic iliofemoral DVT without threatened limb signs.+
- 1Start therapeutic anticoagulation and document onset, baseline function, survival, bleeding and anatomy.
- 2Consider catheter-directed thrombolysis only when symptoms are under fourteen days, function good, survival at least one year and bleeding risk low.
- 3Explain uncertain overall PTS prevention, possible symptom benefit, procedural failure and bleeding before selection.
- 4After intervention address residual iliac obstruction selectively and maintain ordinary DVT anticoagulation duration.
03Conservative pathwayAnticoagulate and reassessFrailty, late presentation or bleeding risk makes early removal unsuitable.+
- 1Choose an anticoagulant after renal, cancer and pregnancy review and set a three-month endpoint.
- 2Use elevation and mobilisation as tolerated while monitoring PE, progression and bleeding.
- 3Arrange review for residual obstruction, venous claudication and post-thrombotic symptoms.
04Pregnancy pathwayCoordinate obstetric careIliofemoral DVT or phlegmasia occurs in pregnancy or puerperium.+
- 1Use urgent objective imaging and immediate LMWH unless contraindicated without using Wells or D-dimer exclusion.
- 2Coordinate maternal rescue, fetal issues, neuraxial timing and intervention with the full specialist team.
- 3Continue therapeutic LMWH through pregnancy and at least six weeks postpartum, with at least three months total treatment.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Enoxaparin sodium
For iliac thrombosis give 100 IU/kg (1 mg/kg) subcutaneously every 12 hours; at CrCl 15–30 mL/min use 1 mg/kg subcutaneously once daily.Contraindicated with active significant bleeding or immune-mediated HIT within 100 days. Not recommended below CrCl 15 outside dialysis-circuit use. Pregnancy dosing follows early-pregnancy weight; plan neuraxial timing and continue through the obstetric duration endpoint.
Apixaban
For an eligible stable non-pregnant adult give 10 mg orally twice daily for 7 days then 5 mg twice daily; review at 3 months and use 2.5 mg twice daily only after 6 months for selected extended prevention.Avoid active bleeding and hepatic coagulopathy. Use cautiously at CrCl 15–29 and not below 15 mL/min or in dialysis. Avoid pregnancy and make a breastfeeding-versus-treatment decision. Coordinate interruption around invasive treatment.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Pulmonary embolism
Extensive proximal thrombus can embolise into the pulmonary circulation, producing hypoxaemia, pleuritic pain, syncope, obstructive shock or sudden death.
Venous gangrene
Near-complete venous outflow obstruction can collapse microvascular perfusion, causing progressive tissue necrosis, secondary arterial compromise and possible major amputation.
Compartment syndrome
Massive fluid sequestration can raise pressure within fixed fascial compartments, causing ischaemic nerve and muscle injury unless surgical decompression occurs promptly.
Post-thrombotic syndrome
Residual venous obstruction and valve reflux sustain ambulatory venous hypertension, causing chronic pain, swelling, venous claudication, skin change and sometimes ulceration.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Repeat limb colour, temperature, refill, arterial signals, sensation, movement and compartment findings.
- Track haemodynamics, urine output, renal function, haemoglobin, platelets, coagulation and fibrinogen.
- After intervention assess access sites, retroperitoneal or intracranial bleeding and restored outflow.
- Continue anticoagulation to at least the standard endpoint and review at three months.
- Assess chronic swelling, heaviness, claudication, skin change and ulceration.
- Ensure pregnancy treatment reaches six postpartum weeks and three months total.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Venous obstruction threatens arteries
Extreme tissue pressure can impair arterial inflow despite thrombosis beginning in veins.
Anatomy defines evidence
Early removal is considered for iliofemoral disease and rejected for femoral, popliteal or calf-only clot.
Time predicts success
Recent thrombus is more removable than organised chronic material, matching the fourteen-day criterion.
Stents preserve anticoagulation
Treating residual iliac stenosis does not remove the original recurrence biology or treatment duration.
Imaging follows urgency
Central mapping can help planning but must never postpone heparin, elevation, fluids or rescue referral.
11Common pitfallsFrequent interpretation and management errors.
- 01
Waiting for routine imaging in cyanotic phlegmasia.
- 02
Ignoring the four thrombolysis criteria.
- 03
Removing calf-only thrombus invasively without established benefit.
- 04
Stopping anticoagulation prematurely after venous stenting.
- 05
Letting CT delay emergency treatment.
- 06
Using DOACs for acute treatment during pregnancy.