Which set of factors constitutes the Virchow triad for venous thrombosis?

• A. Hypercoagulable state, venous stasis, and vascular injury
• B. Hypercoagulable state, venous stasis, and endothelial injury
• C. Endothelial dysfunction, dehydration, and infection
• D. Vascular injury, edema, and thrombocytopenia

Answer: (B)

The fundamental idea is that venous thrombosis tends to form when three conditions coexist: a tendency to clot (hypercoagulable state), slow or stagnant blood flow (venous stasis), and damage to the lining of the blood vessel (endothelial injury). A hypercoagulable state pushes the coagulation cascade forward, increasing thrombin and fibrin formation. Venous stasis slows the clearance of activated clotting factors and platelets, letting a clot develop rather than being washed away. Endothelial injury exposes subendothelial collagen and tissue factor, promoting platelet adhesion and activation of coagulation, which further drives clot formation. Together, these factors create a prothrombotic environment in veins. The option that lists hypercoagulable state, venous stasis, and endothelial injury matches this triad precisely. Other choices include terms like vascular injury instead of endothelial injury, or include dehydration, infection, edema, or thrombocytopenia, which are not part of the classic triad, though they can influence thrombotic risk in various contexts.