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'''Venous thrombosis''' is a fairly common type of thrombus in the veterinary species because veins are relatively thin-walled and are therefore more susceptible to distortion, inflammatory damage and iatrogenic venepuncture damage. Also,veins have relatively slower blood flow rates allowing cell aggregates to persist more readily. Most venous thrombosis in domestic animals results from extension of inflammatory reactions, erosion/disruption caused by malignant tumours, pressure from adjacent space-occupying masses or venepuncture damage.  

'''Venous thrombosis''' is a fairly common type of thrombus in the veterinary species because veins are relatively thin-walled and are therefore more susceptible to distortion, inflammatory damage and iatrogenic venepuncture damage. Also,veins have relatively slower blood flow rates allowing cell aggregates to persist more readily. Most venous thrombosis in domestic animals results from extension of inflammatory reactions, erosion/disruption caused by malignant tumours, pressure from adjacent space-occupying masses or venepuncture damage.  

'''Capillary thromboses''' are microthrombi that are only appreciable histologically. Their formation may be localised and associated with acute local inflammation or generalised. Localised microthrombi are rarely significant unless they are strategically sited. Generalised microthrombi may be seen in terminal diseases as a reflection of vascular failure, and are often associated with [[Shock|shock syndromes]] as part of [[Disseminated Intravascular Coagulopathy|disseminated intravascular coagulation]]. Clinically, generalised capillary thrombosis is highly significant.  

'''Capillary thromboses''' are microthrombi that are only appreciable histologically. Their formation may be localised and associated with acute local inflammation or generalised. Localised microthrombi are rarely significant unless they are strategically sited. Generalised microthrombi may be seen in terminal diseases as a reflection of vascular failure, and are often associated with [[Shock|shock syndromes]] as part of [[Disseminated Intravascular Coagulation|disseminated intravascular coagulation]]. Clinically, generalised capillary thrombosis is highly significant.  

== Signalment ==

== Signalment ==

Angiography may show lack of opacity in the affected region.  

Angiography may show lack of opacity in the affected region.  

On microscopic examination, the thrombus appears as a layered mass which is attached to the vessel wall. The composition consists of [[Red Blood Cells|red blood cells]], [[neutrophils]] and [[platelets]] bound together by fibrin. Thrombi take different appearance depending on whether they are arterial or venous. '''Arterial thrombi''' tend to be '''pale''' and have a tail in the direction of blood flow. The high rate of blood flow sweeps red cells away - the thrombus is composed of mainly white cells, platelets and fibrin which are left behind. '''Venous thrombi''' tend to be a '''darker red'''. The slow blood flow allows the clot to form quicker which is loosely arranged and contains many red blood cells.

On microscopic examination, the thrombus appears as a layered mass which is attached to the vessel wall. The composition consists of [[Red Blood Cell|red blood cells]], [[neutrophils]] and [[platelets]] bound together by fibrin. Thrombi take different appearance depending on whether they are arterial or venous. '''Arterial thrombi''' tend to be '''pale''' and have a tail in the direction of blood flow. The high rate of blood flow sweeps red cells away - the thrombus is composed of mainly white cells, platelets and fibrin which are left behind. '''Venous thrombi''' tend to be a '''darker red'''. The slow blood flow allows the clot to form quicker which is loosely arranged and contains many red blood cells.

== Treatment ==

== Treatment ==

 

The mainstay of treatment is to diagnose and treat the underlying problem.  

The mainstay of treatment is to diagnose and treat the underlying problem.  

== Prognosis ==

== Prognosis ==

 

Prognosis depends upon the underlying condition.  

Prognosis depends upon the underlying condition.  

# Organisation; a thrombus acts as a foreign body, causing an inflammatory response in the underlying blood vessel or heart wall. The external surface of the thrombus then quickly becomes covered by endothelium and is excluded from the clotting mechanism. Neutrophils invade the mass and may reduce the centre. Occasionally, subsequent invasion by bacteria may lead to purulent inflammation. Normally, fibroblasts and capillary buds follow the neutrophils into the thrombus and a fibrous vascularised connective tissue forms. Capillaries channels anastomose to produce vessels that traverse the thrombus and re-establish blood flow - this is known as '''canalisation''' of a thrombus. Fibrous tissue matures and contracts, eventually causing the thrombus to become incorporated into the vessel wall as a fibrous lump. A piece of the thrombus may break off and form an [[Embolism|embolus]].  

# Organisation; a thrombus acts as a foreign body, causing an inflammatory response in the underlying blood vessel or heart wall. The external surface of the thrombus then quickly becomes covered by endothelium and is excluded from the clotting mechanism. Neutrophils invade the mass and may reduce the centre. Occasionally, subsequent invasion by bacteria may lead to purulent inflammation. Normally, fibroblasts and capillary buds follow the neutrophils into the thrombus and a fibrous vascularised connective tissue forms. Capillaries channels anastomose to produce vessels that traverse the thrombus and re-establish blood flow - this is known as '''canalisation''' of a thrombus. Fibrous tissue matures and contracts, eventually causing the thrombus to become incorporated into the vessel wall as a fibrous lump. A piece of the thrombus may break off and form an [[Embolism|embolus]].  

<b>Also see: [[Thromboembolosm]].</b>

<b>Also see: [[Thromboembolism]].</b>

== References ==

== References ==