CLOTTING FACTORS and HEPATITIS/LIVERDISEASE
Prothrombin Time
The liver manufactures most of the clotting factors that the body uses to stop bleeding. The time it takes to produce a clot, called the prothrombin time (PT), generally runs from nine to eleven seconds. Vitamin K is an important factor in the blood clotting process. If the liver is very seriously damaged or if a vitamin K deficiency is present (as sometimes occurs in cholestatic liver diseases such as primary biliary cirrhosis), the PT will run much longer than normal, thereby increasing the risk of excessive bleeding. In some cases, injections of vitamin K can help the PT return to normal. Improvement of the PT with a vitamin K injection indicates that the liver is still functioning. When the PT does not normalize after a vitamin K injection, a condition known as a coagulopathy (a tendency to bleed excessively), severe liver damage, and/or liver failure may exist.
To adjust for variation among laboratories in calibrating the PT, the international ratio (INR) is often used. However, additional research is needed before the INR can be applied to people with liver disease.
Platelets
Platelets are blood cells that help the blood form clots. The spleen plays a role in the storage of platelets. In people with cirrhosis, the spleen works overtime to compensate for the decreased functional abilities of the damaged liver. This is associated with and enlarged spleen (splenomegaly), and a low platelet count known as thrombocytopenia. A normal platelet count is 150 to 450x103/microliter. If a patient has a value lower than 150x103/microliter, thrombocytopenia is said to be present and cirrhosis should be contemplated as a diagnosis.
Copyright © Melissa Palmer 2005
All contents of this article are Copyright © Melissa Palmer, MD
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