- Clinical science
Deep vein thrombosis (DVT) is the formation of a blood clot in a deep vein of the legs, thigh, or pelvis. Thrombosis is most often seen in individuals with a history of immobilization, obesity, malignancy, or hereditary thrombophilia. Vascular endothelial damage, venous stasis, and hypercoagulability, collectively referred to as the Virchow triad, are the main factors contributing to the development of DVT. Symptoms usually occur unilaterally and include swelling, tenderness, and redness or discoloration. Pulmonary embolism (PE), a severe complication of DVT, should be suspected in patients with dizziness, dyspnea, and fever. The diagnostic test of choice for DVT is compression ultrasound. In most cases, a negative D-dimer test allows thrombosis or PE to be ruled out, but a positive test is nonspecific. Initial acute treatment of DVT consists of anticoagulation with heparin and, if the thrombus is large or unresponsive to anticoagulation, may also include thrombolysis or thrombectomy. Secondary prophylaxis is achieved with oral warfarin or direct factor Xa inhibitors and supportive measures such as regular exercise and compression stockings.
- History of DVT or PE (30x increased risk) 
- Immobilization: e.g., post-surgery, long-distance flights, trauma (20x increased risk)
- Age > 60 years
- ) (especially
- Pregnancy, estrogen use (oral contraceptives)
- IV drug use
- Nephrotic syndrome
- Insufficient thrombosis prophylaxis, noncompliance with prophylaxis
To remember the risk factors of deep vein thrombosis, think “THROMBOSIS”: Travel, Hypercoagulable/HRT, Recreational drugs, Old (> 60), Malignancy, Blood disorders, Obesity/Obstetrics, Surgery/Smoking, Immobilization, Sickness (CHF/MI, IBD, nephrotic syndrome, vasculitis)!
The Virchow triad
The Virchow triad refers to the three main pathophysiological components of thrombus formation.
- Hypercoagulability: increased platelet adhesion, (e.g., ), use of oral contraceptives, pregnancy
- Endothelial damage: inflammatory or traumatic vessel injuries can lead to activation of clotting factors through contact with exposed subendothelial collagen
- Venous stasis: varicosis, external pressure on the extremity, immobilization (e.g., hospitalization, bed rest, long flights or bus rides), local application of heat
To remember the three pathophysiological components of thrombus formation, think: “HE'S Virchow”: H-Hypercoaguability, E-Endothelial damage, S-Stasis.
- May be asymptomatic
Localized unilateral symptoms
- Typically affects deep veins of the legs, thighs, or pelvis
- Swelling, feeling of tightness or heaviness
- Warmth, erythema, and possibly livid discoloration
- Progressive tenderness, dull pain
- Distention of superficial veins
- Distal pulses are normal
- General symptoms: fever 
- Possible signs of : dyspnea, chest pain, dizziness, weakness
- Definition: : a severe form of phlebothrombosis, characterized by obstruction of all veins of one extremity with subsequent restriction of arterial flow; and associated with a high mortality
- Complications: shock, gangrene, acute renal failure (due to rhabdomyolysis)
Paget-Schroetter disease (upper extremity DVT)
- Definition: acute thrombosis of a brachial, axial, or subclavian vein
- Treatment: anticoagulation, fibrinolysis
|Medical history||Active cancer||+1|
|Previously documented DVT||+1|
|Immobilization||Paralysis or recent (cast) immobilization of lower extremity||+1|
|Clinical symptoms||Tenderness localized along the deep venous system||+1|
|Swelling of the entire leg||+1|
|Calf swelling ≥ 3 cm compared to asymptomatic calf||+1|
|Unilateral pitting edema in symptomatic leg||+1|
|Presence of collateral (non-varicose) superficial veins||+1|
|Differential diagnosis||Alternative diagnosis at least as likely as DVT||-2|
Compression ultrasonography with Doppler (test of choice)
- A combination of ultrasonography (to visualize the vein) and Doppler (to assess blood flow abnormalities) in which the examiner applies gentle pressure to normally compressible veins using an ultrasound probe
- High sensitivity and specificity in the popliteal and femoral veins, but very operator dependent
- Indications: clinical suspicion of a DVT or pulmonary embolism
- Findings: noncompressibility of the obstructed vein, visible hyperechoic mass, absent or abnormal flow in Doppler imaging
- High sensitivity (∼ 95%), low specificity (∼ 50%)
- Useful for ruling out DVT (normal D-dimer levels rule out DVT)
- Elevated D-dimers alone are not proof of DVT.
Further diagnostic tests
- Venography: (angiography)
- CT scan: : suspected or underlying malignancy
Thrombophilia screening ( )
- Indications: young patients, unusual thrombus localization, positive family history
- At earliest, tests should be performed 2 weeks after discontinuing anticoagulation.
- General tumor screening
- Definition: Inflammation and thrombosis of a superficial vein, most commonly in the leg. It may co-exist with DVT, and it rarely causes PE.
Risk factors: same as for DVT (see risk factors for deep vein thrombosis above), but also
- Varicose veins
- Venous cannulation, IV drug administration
- Clinical features: pain, tenderness, induration, and erythema overlying a superficial vein, often with a palpable cord (the thrombosed vein)
Other differential diagnoses of DVT
- Muscle or soft tissue injury (i.e., posttraumatic swelling or hematoma)
- Ruptured popliteal cyst
The differential diagnoses listed here are not exhaustive.
- Acute therapy
Warfarin with target therapeutic INR of 2.0–3.0
- Duration of treatment
- First thrombosis: usually 3–6 months
- For confirmed thrombophilia and recurrent thrombosis: indefinite
- Duration of treatment
OR direct oral factor Xa inhibitor (i.e., rivaroxaban, apixaban)
- Regular monitoring of coagulation parameters not required → improved patient compliance
- Duration of treatment: at least 3 months
- Warfarin with target therapeutic INR of 2.0–3.0
- Goal: faster resolution of thrombi
- Agents: streptokinase, urokinase, tissue plasminogen activator
- Catheter-directed thrombolysis: The thrombolytic agent is administered directly at the site of obstruction via a venous catheter.
- Inferior vena cava filter : (Greenfield filter): indicated in patients with DVT at high risk of developing pulmonary embolism who have contraindications to anticoagulation, thrombolysis, and thrombectomy (e.g., active bleeding, recent major surgery, recent intracranial hemorrhage)
- Compression therapy with bandages or compression stockings
- Early mobilization as early as tolerated, minimize bedrest.
We list the most important complications. The selection is not exhaustive.
- Preventive measures
Indications (based on assessment of risk factors; see “Etiology” above)
- Low thrombosis risk: exercise, compression stockings
- Medium and high thrombosis risk: anticoagulation treatment