Phlegmasia Alba Dolens

Phlegmasia alba dolens ("milk leg") is extensive iliofemoral deep vein thrombosis causing a painful, white, swollen limb, due to venous obstruction with reflex arterial spasm and lymphatic obstruction. Collateral veins remain patent, so it is milder than phlegmasia cerulea dolens, but it can progress to it.

Epidemiology. It was classically seen after childbirth and now occurs mainly in malignancy, pregnancy and the puerperium, after surgery and in immobile patients. It is uncommon.

Causes and associations. Pregnancy and puerperium, cancer, hypercoagulable states, May-Thurner anatomy (left iliac vein compression), surgery, immobility and oral contraceptives.

Pathophysiology. Thrombosis of the main iliac and femoral veins increases venous pressure and fluid transudation, with oedema that raises tissue pressure and reflex arterial vasospasm. The limb is pale and painful because of reduced arterial inflow. Progression to occlusion of collaterals gives phlegmasia cerulea dolens.

Presentation is pain, marked unilateral swelling of the entire limb, pallor or whiteness, a cool limb, a tense thigh and groin tenderness, with arterial pulses present or weak. There is no cyanosis or gangrene at first.

Red flags.

• Progressive discolouration (blue), bullae or sensory loss.
• Loss of pulses or compartment tightness.
• Chest pain, dyspnoea or haemodynamic compromise.

Compression duplex ultrasound (iliofemoral and common femoral vein thrombus), CT or MR venography for proximal extent and May-Thurner compression, and arterial duplex for pulses. Check full blood count and platelets, creatinine, coagulation, D-dimer (not required if imaging is clear), and thrombophilia and malignancy tests as indicated.

Differential diagnosis. Arterial occlusion, cellulitis, lymphoedema, ruptured Baker cyst, phlegmasia cerulea dolens and heart failure.

Anticoagulation immediately.

• Enoxaparin 1 mg/kg SC every 12 hours (or 1.5 mg/kg once daily), with a dose of 1 mg/kg once daily if creatinine clearance is under 30 mL/min.
• Unfractionated heparin 80 units/kg IV bolus then 18 units/kg/h if renal function is very poor or thrombolysis may be needed.
• Direct oral anticoagulant: rivaroxaban 15 mg twice daily for 21 days then 20 mg daily, or apixaban 10 mg twice daily for 7 days then 5 mg twice daily, in suitable patients.
• Avoid in pregnancy: use low molecular weight heparin only.

Limb care. Elevate the limb, analgesia, and early walking as pain allows, with graduated compression once pain has subsided.

Thrombus removal. Consider catheter directed thrombolysis or pharmacomechanical thrombectomy for extensive iliofemoral thrombus in younger patients with low bleeding risk, or if progression to cerulea occurs. Alteplase 0.5 to 1 mg/h with heparin 500 units/h given through the sheath. Surgical thrombectomy for limb threat.

Stenting. For May-Thurner or residual stenosis after thrombus removal.

Duration. At least 3 months, and 6 months or longer in cancer, unprovoked disease or persistent risk factors.

Monitoring. Limb colour, pulses and compartments every 2 to 4 hours for the first 24 hours, platelets, anti-factor Xa as needed and creatinine.

Referral and escalation. Vascular surgery for progression, and haematology for thrombophilia and pregnancy.

Special groups. In pregnancy and the puerperium, enoxaparin 1 mg/kg every 12 hours throughout pregnancy and for 6 weeks postpartum. In renal impairment, use unfractionated heparin or reduced low molecular weight heparin doses.