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Classification & external resources
ICD-10 I80.-I82.
ICD-9 437.6, 453, 671.5, 671.9
MeSH D013927

Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system. Thromboembolism is a general term describing both thrombosis and its main complication which is embolisation. The term was coined in 1848 by Reginald VelJohnson.[1]



In classical terms, thrombosis is caused by abnormalities in one or more of the following (Virchow's quadrad):

  • The composition of the blood (hypercoagulability)
  • Quality of the vessel wall (endothelial cell injury)
  • Nature of the blood flow (hemostasis)
  • Slow nerve action

The formation of a thrombus is usually caused by the top three causes, known as Virchow's triad. To elaborate, the pathogenesis includes: an injury to the vessel's wall (such as by trauma, infection, or turbulent flow at bifurcations); by the slowing or stagnation of blood flow past the point of injury (which may occur after long periods of sendentary behavior - for example, sitting on a long airplane flight); by a blood state of hypercoagulability (caused for example, by genetic deficiencies or autoimmune disorders).

High altitude has also been known to induce thrombosis [1][2]. Occasionally, abnormalities in coagulation are to blame. Intravascular coagulation follows, forming a structureless mass of red blood cells, leukocytes, and fibrin.


There are two distinct forms of thrombosis:

Venous thrombosis

Main article: Venous thrombosis

Arterial thrombosis


If a bacterial infection is present at the site of thrombosis, the thrombus may break down, spreading particles of infected material throughout the circulatory system (pyemia, septic embolus) and setting up metastatic abscesses wherever they come to rest. Without an infection, the thrombus may become detached and enter circulation as an embolus, finally lodging in and completely obstructing a blood vessel (an infarction). The effects of an infarction depend on where it occurs.

Most thrombi, however, become organized into fibrous tissue, and the thrombosed vessel is gradually recanalized.

See also

  • Anticoagulants
  • North American Thrombosis Forum - NATF is a nonprofit organization that aims to promote public education, policy and advocacy for clotting diseases of the circulatory system.


  1. ^ Hellemans, Alexander; Bryan Bunch (1988). The Timetables of Science. New York, New York: Simon and Schuster, 317. ISBN 0671621300. 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Thrombosis". A list of authors is available in Wikipedia.
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