Overview
Definition
The formation of a blood clot (thrombus) within a deep vein, most commonly in the legs.
Epidemiology
A common and potentially life-threatening condition due to the risk of embolization.
Etiology & Risk Factors
- Virchow's Triad: (1) Venous stasis (immobility, long flights, surgery), (2) Endothelial injury (trauma, surgery), (3) Hypercoagulability (cancer, pregnancy, Factor V Leiden mutation, oral contraceptives).
Clinical Symptoms
- Unilateral leg swelling (edema)
- Calf pain, tenderness, or cramping
- Warmth and erythema over the affected vein
- Homan's sign (calf pain with dorsiflexion of the foot) - unreliable, but classically taught
Clinical Approach
Diagnosis
- Wells Score: Used to determine pre-test probability
- D-dimer: Highly sensitive but not specific. Useful to RULE OUT DVT in low-risk patients (a negative D-dimer means no DVT).
- Venous Doppler Ultrasound (Gold Standard): Demonstrates non-compressibility of the vein due to the clot
Management
- Anticoagulation is the mainstay of therapy (prevents clot extension and embolization, does NOT dissolve the existing clot)
- Direct Oral Anticoagulants (DOACs, e.g., Apixaban, Rivaroxaban) are often first-line
- Low Molecular Weight Heparin (LMWH) bridged to Warfarin is an alternative
- IVC Filter: Indicated ONLY if anticoagulation is strictly contraindicated (e.g., active major bleeding)
Complications
- Pulmonary Embolism (PE) - the most feared complication, when the clot breaks off and travels to the lungs
- Post-thrombotic syndrome (chronic leg swelling, pain, and venous ulcers)