Deep vein thrombosis

Deep vein thrombosis is a blood clot that forms in a deep vein, most often in the leg. It can obstruct blood flow and may lead to a pulmonary embolism if part of the clot travels to the lungs.

Virchow's triad: A framework of venous stasis, vessel-wall injury, and hypercoagulability that describes factors promoting thrombosis. These three conditions help explain how a deep-vein clot forms.
Compression ultrasonography: An ultrasound technique that assesses whether a vein collapses when gentle pressure is applied. Failure of a suspected leg vein to compress supports a DVT diagnosis.
Factor V Leiden: An inherited F5 gene variant that makes coagulation factor V less susceptible to inactivation by activated protein C. This thrombophilia raises the risk of venous clots, including DVT.
Post-thrombotic syndrome: Chronic leg pain, swelling, or skin changes caused by lasting venous damage after DVT. Residual obstruction or damaged valves can leave long-term symptoms.
Superficial thrombophlebitis: Inflammation and clotting in a superficial vein, often producing a tender, palpable cord. It affects veins near the skin rather than the deep veins involved in DVT.
Venous stasis: Slowed or pooled blood flow in veins. Immobility can slow leg-vein flow and favor clot formation.
D-dimer: A fibrin-degradation product measured in blood that can rise when clots form and break down. A negative result can help rule out DVT when clinical probability is low.
Prothrombin G20210A mutation: An inherited F2 gene variant associated with increased prothrombin levels and greater venous thrombosis risk. It is another inherited predisposition to DVT.
Chronic venous insufficiency: Impaired return of blood through the leg veins, often causing swelling and skin changes. A DVT can damage venous valves and contribute to chronic venous hypertension.
Arterial thrombosis: Formation of a clot within an artery, which supplies blood away from the heart. DVT is a venous clot; arterial clots arise in a different circulation and cause different patterns of injury.

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