The liver plays an important role in coagulation:
- synthesis of coagulation factors I, II, V, VII, IX, X. Vitamin K dependent factors - II, VII, IX and X - and Factor V are affected first in disease. Factor VII is the earliest of all to decline because of its short half-life (6 hours). Fibrinogen (factor I) synthesis is affected only in severe disease.
- inhibition of fibrinolysis / coagulation - the liver is responsible for synthesising plasma anticoagulant proteins, e.g. protein C, protein S and antithrombin III.
- clearance of activated coagulation factors - fibrin and tissue plasminogen activator (tPA) are removed from the circulation by the liver's reticuloendothelial system
- absorption of vitamin K - malabsorption occurs in disease
Impairment of any of these mechanisms predisposes to bleeding.