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

Deep Vein Thrombosis of the Right Leg

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).
Clinical Feature Points
Active cancer 1
Paralysis, paresis, or immobilization of lower extremity 1
Recently bedridden for more than 3 days, or major surgery within the past 12 weeks 1
Localized tenderness along the distribution of the deep venous system 1
Entire leg swelling 1
Calf swelling at least 3 cm larger than asymptomatic side (measured 10 cm below tibial tuberosity) 1
Pitting edema confined to symptomatic leg 1
Collateral non-varicose veins 1
Previously diagnosed DVT or PE 1

Interpretation:

  • A score of 0 or less: low probability of DVT

  • A score of 1-2: moderate probability of DVT

  • A score of 3 or more: high probability of DVT

  • If suspected DVT refer to local DVT clinic

 
Cardiology, HaematologymypanotesDeep Vein Thrombosis (DVT)