Etiology
Risk factors, present in around 50% of documented cases, include malignancy, hyper-coagulable states, cardiac disease, venous stasis, venous insufficiency, May-Thurner syndrome (right iliac artery compressing the left iliac vein that runs beneath it), surgery, trauma, pregnancy, inferior vena cava (IVC) filter, hormone therapy, oral contraceptives, prolonged immobilization, inflammatory bowel disease, heart failure, and central venous catheters. Etiology is unknown in ~10% of PCD cases. Pathophysiology
When a thrombus occludes an extremity vein, pressure backs up in the venous system leading plasma fluid to leak out into the interstitium of the affected limb. This increases the pressure of that limb compartment, which can collapse the arteries and lead to acute ischemia, gangrene, hypovolemia, and hemodynamic instability. Diagnosis
PCD is best diagnosed with contrast venography, but venous duplex ultrasonography is used more commonly in clinical practice. Magnetic resonance and computed tomography venography can also be used. Differential Diagnosis
DDx is as follows:

Cellulitis
Venous insufficiency
Superficial thrombophlebitis
DVT
Arterial embolism
Lymphedema
Ruptured Bakers cyst

Treatment
Treatment for PCD includes immediate anticoagulation, fluid resuscitation, bed rest, limb elevation above 60º, limb wrap to reduce pain and edema, and either catheter-based thrombolysis, percutaneous transluminal angioplasty, or surgical venous thrombectomy +/- fasciotomy to remove the blood clot. Some people also suggest an IVC filter before thrombolysis. Prognosis
PCD is fully reversible if the causal venous thrombus is promptly removed. In the 40-60% of people who go on to develop venous gangrene, there is a 20-50% risk of amputation and 20-40% mortality rate.
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