Deep Vein Thrombosis (DVT)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Patient Advice

Definition

Deep Vein Thrombosis (DVT) is the formation of a blood clot in a deep vein, most commonly in the legs. It can cause pain and swelling and carries a risk of life-threatening complications such as pulmonary embolism (PE). See Figure 1.

Aetiology

DVT results from a combination of factors that contribute to clot formation, known as Virchow's triad:

• Venous Stasis: Reduced blood flow in veins due to immobility, prolonged bed rest, or long-haul flights.
• Endothelial Injury: Damage to the vein wall from trauma, surgery, or inflammation.
• Hypercoagulability: Increased clotting tendency due to conditions such as pregnancy, cancer, or inherited thrombophilias (e.g., Factor V Leiden).

Pathophysiology

DVT develops due to the following processes:

• Clot Formation: Platelets and fibrin aggregate to form a thrombus within the vein.
• Venous Obstruction: The clot obstructs blood flow, leading to swelling and increased venous pressure.
• Risk of Embolisation: The clot may dislodge and travel to the lungs, causing pulmonary embolism.

Risk Factors

Key risk factors include:

• Prolonged immobility (e.g., after surgery or long travel).
• Recent surgery, particularly orthopaedic or pelvic procedures.
• Pregnancy or postpartum period.
• Cancer or chemotherapy.
• Use of oestrogen-containing contraceptives or hormone replacement therapy.
• Obesity or smoking.
• Inherited thrombophilias (e.g., Factor V Leiden mutation).

Signs and Symptoms

Symptoms of DVT include:

• Swelling: Unilateral swelling of the affected leg.
• Pain: Calf or thigh pain, often described as cramping or aching.
• Redness and Warmth: Over the affected area.
• Homan's Sign: Pain in the calf on dorsiflexion of the foot (not specific).

Investigations

Key investigations and common positive findings include:

• Wells Score: A clinical scoring system to assess DVT risk.
• D-dimer Test: Elevated levels indicate active clot formation and breakdown, though not specific for DVT.
• Compression Ultrasound: The diagnostic test of choice. Positive findings include non-compressibility of the affected vein.
• Venography: Used in complex cases to visualise the clot directly, though rarely needed.

Management

1. Primary Care Management

• Immediate Referral: Urgent referral to secondary care if DVT is suspected.
• Initial Anticoagulation: If available, administer low-molecular-weight heparin (e.g., enoxaparin) while awaiting secondary care review.

2. Secondary Care Management

• Anticoagulation Therapy: Start with low-molecular-weight heparin, transitioning to oral anticoagulants such as apixaban or rivaroxaban.
• Monitoring: Regular INR monitoring if using warfarin.
• Thrombolysis: Considered in massive DVT or phlegmasia cerulea dolens, typically performed by an interventional radiologist.
• Inferior Vena Cava (IVC) Filter: For patients with contraindications to anticoagulation, performed by a vascular specialist.

Patient Advice

Key advice includes:

• Take anticoagulants as prescribed and attend regular follow-ups.
• Stay mobile and avoid prolonged immobility.
• Maintain a healthy weight and stop smoking.
• Wear compression stockings to prevent post-thrombotic syndrome, if recommended.
• Seek immediate medical attention for symptoms of pulmonary embolism, such as sudden chest pain or breathlessness.

Figure 1

Image showing a deep vein thrombosis in the right leg, with swelling and redness.

References

1. James Heilman, MD (2015). Deep Vein Thrombosis of the Right Leg [Image]. Available at: https://upload.wikimedia.org/wikipedia/commons/2/21/Deep_vein_thrombosis_of_the_right_leg.jpg (Accessed: 30 December 2024).