In a 45-year-old man with a red, swollen left lower extremity up to the knee, pain that worsens on elevation and distal cyanosis of the toes, what is the most likely diagnosis?

Phlegmasia Cerulea Dolens

This patient has phlegmasia cerulea dolens (PCD), a life-threatening complication of massive deep vein thrombosis that requires immediate anticoagulation and urgent vascular intervention to prevent limb loss and death. 1

Clinical Reasoning

The presentation is pathognomonic for PCD rather than typical DVT or acute limb ischemia:

• Red and swollen leg indicates massive venous congestion with involvement of both deep and collateral venous systems 1
• Pain that worsens with elevation is characteristic of venous pathology (opposite of arterial ischemia, where elevation typically improves pain) 1
• Pale toes when elevated reflects severe venous hypertension causing arterial insufficiency and fluid sequestration 2, 3
• Cyanosis/pallor pattern distinguishes PCD from acute arterial ischemia, which presents with the "6 Ps" (pain, pallor, pulselessness, poikilothermia, paresthesia, paralysis) but without the massive swelling and dusky discoloration seen here 1

PCD represents the most severe end of the DVT spectrum, where thrombosis extends from distal to proximal veins and involves collateral circulation, causing venous hypertension that can progress to arterial compromise, circulatory shock, and venous gangrene 2, 4, 3.

Immediate Management Algorithm

Step 1: Emergency Anticoagulation (Within Minutes)

• Start unfractionated heparin bolus immediately without waiting for imaging confirmation, as delay increases amputation and mortality risk 5, 3
• Target aPTT 1.5-2.5 times control or use weight-based protocol 1
• Do not delay anticoagulation for diagnostic testing in this clinical presentation 1

Step 2: Urgent Diagnostic Imaging (Within 1-2 Hours)

• Order complete duplex ultrasound from inguinal ligament to ankle to confirm extent of thrombosis 1, 6
• If ultrasound shows extensive iliofemoral thrombosis (expected in PCD), proceed immediately to Step 3 2, 7
• Add CT venography or MR venography if ultrasound cannot adequately visualize iliac veins, as isolated iliac thrombosis may be missed 6, 8

Step 3: Urgent Multidisciplinary Consultation (Within 2-4 Hours)

• Immediate vascular surgery consultation for consideration of catheter-directed thrombolysis, mechanical thrombectomy, or surgical thrombectomy 1, 2, 4, 7
• Interventional radiology consultation for endovascular options including ultrasound-accelerated thrombolysis 4, 7
• Standard anticoagulation alone has 40% mortality and up to 50% amputation rate in PCD 2, 3

Step 4: Monitor for Compartment Syndrome

• Assess compartment pressures if leg becomes tense or patient develops paresthesias/paralysis 3
• Emergent fasciotomy required if compartment syndrome develops, as this complication carries extremely high mortality 3
• Monitor for circulatory shock from massive fluid sequestration in the limb 2, 3

Critical Distinguishing Features from Other Diagnoses

Why NOT acute arterial limb ischemia (ALI)?

• ALI presents with a cold, pale leg with absent pulses from the onset 1
• Pain in ALI improves with dependency (gravity helps arterial flow), whereas venous pain worsens 1
• ALI lacks the massive swelling seen in PCD 1
• The red/dusky discoloration in PCD reflects venous congestion, not arterial pallor 1, 2

Why NOT cellulitis?

• Cellulitis does not cause pain worsening with elevation 6
• Cellulitis does not cause distal pallor or cyanosis 6
• Cellulitis typically has more localized erythema with clear borders, not diffuse leg swelling to the knee 6

Why NOT typical DVT?

• Standard DVT presents with unilateral swelling and pain but maintains normal skin color or mild erythema (26% of cases) 9
• PCD is distinguished by cyanosis, massive swelling, and arterial compromise from complete venous occlusion 1, 2
• PCD represents only 1-2% of all DVT cases but requires fundamentally different management 2, 4

Prognostic Factors

• Mortality rate: 25-40% even with treatment 2, 3
• Amputation rate: up to 50% without aggressive intervention 2, 3
• Pulmonary embolism occurs in 30% of PCD cases 2
• Prompt anticoagulation within hours can occasionally achieve complete resolution without thrombolysis, but this is unpredictable and should not delay vascular consultation 5

Common Pitfalls to Avoid

• Do not wait for imaging before starting anticoagulation in this presentation—clinical diagnosis is sufficient 5, 3
• Do not treat with anticoagulation alone without vascular surgery evaluation, as this approach has unacceptably high amputation and mortality rates 2, 3
• Do not mistake this for arterial ischemia and pursue arterial imaging/intervention, which delays appropriate venous treatment 1
• Do not miss compartment syndrome, which can develop rapidly and requires immediate fasciotomy 3