Deep venous thrombosis

Deep venous thrombosis (DVT) is the formation of a blood clot (thrombus) in a deep vein, most commonly affecting the lower extremities. It is a potentially serious condition due to the risk of pulmonary embolism (PE), a life-threatening complication where the clot dislodges and travels to the lungs.

Pathophysiology

Deep venous thrombosis occurs due to abnormalities in Virchow’s triad, which includes:

• 1. Venous stasis – Slow or reduced blood flow, often due to prolonged immobility.
• 2. Endothelial damage – Injury to the inner lining of the vein, increasing clot formation.
• 3. Hypercoagulability – A tendency for the blood to clot more than normal.

When a clot forms, it may:

• Partially or completely obstruct venous return.
• Cause local inflammation and swelling.
• Dislodge and travel as an embolus, potentially leading to pulmonary embolism.

Risk Factors

Several factors increase the likelihood of developing deep venous thrombosis:

• Immobility – Long-distance travel, prolonged bed rest, or recent surgery.
• Recent surgery or trauma – Especially orthopedic procedures involving the hip, knee, or spine.
• Pregnancy and postpartum period – Increased clotting tendency due to hormonal changes.
• Hormonal therapy – Use of oral contraceptives or hormone replacement therapy.
• Cancer – Malignancies can induce a prothrombotic state.
• Genetic predisposition – Conditions like factor V Leiden mutation or prothrombin gene mutation.
• Obesity – Excess weight increases venous pressure.
• Smoking – Damages blood vessels and increases clot risk.

Clinical Presentation

The symptoms of deep venous thrombosis can vary depending on clot size and location, but common signs include:

• Unilateral leg swelling – Affected leg may appear larger than the other.
• Pain and tenderness – Especially along the calf or inner thigh.
• Redness and warmth – Over the affected area.
• Dilated superficial veins – Due to venous obstruction.

In severe cases, DVT can cause phlegmasia cerulea dolens, a condition characterized by massive swelling, pain, and bluish discoloration, leading to possible gangrene.

Diagnosis

Deep venous thrombosis is diagnosed using a combination of clinical assessment and imaging studies.

Clinical Assessment

The Wells score for DVT is commonly used to assess risk, with criteria such as:

• Active cancer.
• Recent immobilization or surgery.
• Localized tenderness.
• Leg swelling.
• Pitting edema.
• History of DVT.

Diagnostic Tests

• D-dimer test – A blood test that detects fibrin degradation products; a negative result suggests a low probability of DVT.
• Compression ultrasound – The gold standard for diagnosing DVT; shows lack of venous compressibility.
• Venography – A contrast-enhanced X-ray test, rarely used today.
• Magnetic resonance venography (MRV) – Useful in cases of suspected pelvic vein thrombosis.

Treatment

The goals of treatment for deep venous thrombosis include preventing clot propagation, reducing symptoms, and avoiding complications.

Anticoagulation Therapy

Most patients require anticoagulation for at least 3–6 months:

• Low-molecular-weight heparin (Enoxaparin, Dalteparin) – Common in initial treatment, especially for cancer-associated thrombosis.
• Direct oral anticoagulants (DOACs) – Such as rivaroxaban, apixaban, and dabigatran, preferred due to their ease of use.
• Warfarin – Requires international normalized ratio (INR) monitoring, but still used in select cases.

Thrombolytic Therapy

For massive DVT or phlegmasia cerulea dolens, thrombolysis may be considered:

• Catheter-directed thrombolysis – Uses medications like tPA (tissue plasminogen activator) to dissolve the clot.
• Surgical thrombectomy – Considered in life-threatening cases.

Inferior Vena Cava (IVC) Filter

Placed in patients who:

• Have contraindications to anticoagulation.
• Have recurrent emboli despite therapy.
• Are at high risk of pulmonary embolism.

Complications

If untreated, deep venous thrombosis can lead to:

• Pulmonary embolism (PE) – A dislodged clot blocking a pulmonary artery, causing dyspnea, chest pain, and tachycardia.
• Post-thrombotic syndrome (PTS) – Chronic pain, swelling, and skin changes due to long-term venous damage.
• Chronic venous insufficiency – Leading to leg ulcers and persistent edema.

Prevention

For individuals at risk, preventive measures are crucial:

• Early ambulation after surgery to reduce stasis.
• Compression stockings to promote venous return.
• Intermittent pneumatic compression (IPC) devices for immobile patients.
• Prophylactic anticoagulation in high-risk individuals.

Epidemiology

Deep venous thrombosis affects 1 in 1000 adults per year, with a higher incidence in:

• Older adults.
• Hospitalized patients.
• Individuals with genetic clotting disorders.

DVT is a leading cause of preventable hospital-related mortality, often due to undiagnosed pulmonary embolism.

Related pages

• Pulmonary embolism
• Venous thromboembolism
• Anticoagulation therapy
• Post-thrombotic syndrome
• Inferior vena cava filter