thrombosis - Causes, Types/classification, Embolisation

The formation of a blood clot within a blood vessel, resulting in a partial or complete blockage. Its basis is the formation of the protein, fibrin, which is formed from a soluble precursor, fibrinogen. Fibrin forms a mesh in which platelets and red blood cells are trapped, and produces a plug to the flow of blood. The conversion of fibrinogen to fibrin is activated by a complex series of enzymes which include 13 coagulation factors and requires calcium ions. The process is initiated by contact of the blood with damaged blood vessels and tissues and often occurs on a patch of atherosclerosis. Thrombosis may occur within any artery or vein in the body. Myocardial infarction or stroke result when the coronary or cerebral arteries are blocked. Thrombosis within veins, particularly in the legs, may break off and give rise to an embolus.

Thrombosis
Classifications and external resources

ICD-10	I80-I82
ICD-9	437.6, 453, 671.5, 671.9

Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system.

Causes

Classically, thrombosis is caused by abnormalities in one or more of the following (Virchow's triad):

The composition of the blood Quality of the vessel wall Nature of the blood flow

The formation of a thrombus is usually caused by an injury to the vessel's wall, either by trauma or infection, and by the slowing or stagnation of blood flow past the point of injury.

Types/classification

There are two distinct forms of thrombosis:

Venous thrombosis Deep venous thrombosis Portal vein thrombosis Renal vein thrombosis hepatic vein thrombosis (Budd-Chiari syndrome) Paget-Schroetter disease (upper extremity vein) Thoracic outlet syndrome (the cause of most Subclavian Vein Thrombosis unrelated to trauma) Arterial thrombosis Cerebrovascular accident (ischaemic strokes are either thrombotic or embolic) Myocardial infarction (usually coronary thrombosis due to rupture of an atherosclerotic plaque) Thoracic outlet syndrome (may precipitate arterial thrombosis as well as venous)

Embolisation

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.