Difference between revisions of "Thrombosis"
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− | + | [[Image:Pulmonary artery thrombus.jpg|right|thumb|125px|<small><center>'''Pulmonary artery thrombus'''. Courtesy of A. Jefferies</center></small>]] | |
− | + | '''''Thrombosis''''' may be due to: | |
− | [[Image:Pulmonary artery thrombus.jpg|thumb| | + | *Endothelial injury. |
− | + | *Altered blood flow E.g. abnormal stasis. | |
− | + | *Hypercoagulability. | |
− | + | Often associated with other disease processes for example [[Disseminated Intravascular Coagulation|Disseminated intravascular coagulation]]. | |
− | + | Commonly see [[Atrial_Thrombosis|posterior paralysis]] of cats with cardiomyopathy. | |
− | Spontaneous venous thrombosis is rare | + | Spontaneous venous thrombosis is rare. Seen in cattle with traumatic reticulo-peritonitis in the caudal vena cava. |
− | |||
− | |||
− | ''' | + | [[Image:thrombosis dog nose.jpg|right|thumb|125px|<small><center>'''Nasal thrombosis (dog)'''. Courtesy of T. Scase</center></small>]] |
− | '''[[ | + | [[Image:thrombosis dog nose 2.jpg|right|thumb|125px|<small><center>'''Nasal thrombosis (dog)'''. Courtesy of T. Scase</center></small>]] |
+ | [[Image:sarcoma embolus.jpg|right|thumb|125px|<small><center>'''Sarcoma embolus (dog)'''. Courtesy of T. Scase</center></small>]] | ||
− | + | [[Image:DIC thrombus.jpg|right|thumb|125px|<small><center>'''DIC thrombus'''. Courtesy of A. Jefferies</center></small>]] | |
− | |||
− | ''' | + | [[Image:Pulmonary artery thrombus.jpg|right|thumb|125px|<small><center>'''Pulmonary artery thrombus'''. Courtesy of A. Jefferies</center></small>]] |
− | + | ===Description=== | |
− | + | Thrombosis is a localized or generalized intravascular clot formation. Thrombi form as the result of trauma or pathological processes affecting the blood vessel endothelium or disturbances to blood flow and/or blood composition. Some diseases such as infective endocarditis and heart worm increase the risk of thrombi formation. | |
− | + | ===Diagnosis=== | |
− | == Clinical Signs == | + | ====History & Clinical Signs==== |
− | Signs depend on the area affected and the size of the vessel | + | *Signs depend on the area affected and the size of the blocked vessel. |
− | + | *Poor perfusion below affected area. | |
− | |||
− | |||
− | + | *Malfunction and necrosis of affected organs | |
− | |||
− | + | ====Laboratory Findings==== | |
− | + | Abnormalities associated with lack of blood perfusion and/or pathological conditions. | |
− | |||
− | + | ====Ultrasonography==== | |
− | + | *Blood stasis | |
− | |||
− | |||
− | + | *Visualization of a thrombus | |
− | |||
− | |||
− | |||
− | + | ====Angiography==== | |
− | + | *May show lack of opacity in affected region | |
− | |||
− | + | ===Treatment=== | |
− | + | -Treat underlying problem | |
− | + | -IV Fluids | |
− | + | -Anticoagulant (Heparin for short term treatment, Aspirin for long term treatment) | |
− | + | ===Prognosis=== | |
− | + | -Depends on underlying condition | |
− | |||
− | [[ | + | |
− | [[ | + | =From general pathology= |
− | [[ | + | |
− | [[ | + | ==Introduction== |
− | [[Category: | + | |
− | [[Category: | + | * A thrombus is a solid blood clot that forms within the vessels or heart during life. |
− | [[Category: | + | ** The process of thrombus formation is known as thrombosis. |
− | [[Category: | + | ** Thrombii may occur anywhere within the cardiovascular system. |
+ | |||
+ | ===Thrombosis=== | ||
+ | |||
+ | * The process usually begins with platelets becoming sticky. | ||
+ | ** Adhere to each other and to the endothelium. | ||
+ | * This increased "stickiness" is induced by contact with: | ||
+ | ** Collagen | ||
+ | ** Basement membrane | ||
+ | ** Damaged endothelial cells | ||
+ | ** Bacteria | ||
+ | |||
+ | ===Appearance of a Thrombus=== | ||
+ | |||
+ | * A thrombus is a layered mass which is attached to the vessel wall. | ||
+ | * The composition of a thrombus consists of red blood cells, [[[[Neutrophils|Neutrophils]] - WikiBlood|neutrophils]] and platelets bound together by fibrin. | ||
+ | * Thrombi take different appareance 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. | ||
+ | *** Loosely arranged. | ||
+ | *** Contains many red blood cells. | ||
+ | |||
+ | ==Causes of Thrombosis== | ||
+ | |||
+ | * Thrombosis is caused by any condition that allows platelets to adhere to the endothelial wall. | ||
+ | |||
+ | ===Damage to the Vessel Wall=== | ||
+ | |||
+ | * When there is damage of the overlying endothelium, collagen is exposed and platelets will attach to this. | ||
+ | ** The blood clotting process will occur, giving formation of an intraluminal blood clot. | ||
+ | *** The process of formation occurs in phases giving a cross section of the clot a laminated appearance. | ||
+ | * Vessel walls may be damaged in several ways: | ||
+ | ** Trauma | ||
+ | ** Localisation by colonies of bacteria | ||
+ | ** Viral infection of endothelial cells | ||
+ | ** Migration of parasites. | ||
+ | * Repeated puncture of the jugular vein is a common cause of serious or fatal thrombosis. | ||
+ | |||
+ | ===Changes in Normal Blood Flow=== | ||
+ | |||
+ | ====Stasis==== | ||
+ | |||
+ | * Stasis prevents coaglation factors being cleared by the liver and reticuloendothelial system. | ||
+ | * Coagulation factors build up, leading to clot formation. | ||
+ | * When stasis occurs in a vein, the thrombus forms behind the valve cusps. | ||
+ | ** Quickly enlarges to fill the lumen. | ||
+ | |||
+ | ====Turbulence==== | ||
+ | |||
+ | * Turbulence disrupts the laminar flow. | ||
+ | ** Platelets are brought into contact with the endothelial wall and may even damage the endothelium. | ||
+ | * Thrombi tend to form at arterial branches and venous junctions where there are eddy currents and local stasis. | ||
+ | |||
+ | ===Changes in Blood Composition=== | ||
+ | |||
+ | * An increase in the number and adhesiveness of platelets, or in plasma fibrin and clotting factors results in a hypercoagulateable state | ||
+ | * There may also be a decrease in the activity of the fibrinolyltic system. | ||
+ | * This may be caused by surgical or traumatic shock, or inflammation with toxaemia. | ||
+ | |||
+ | ==Types of Thrombosis== | ||
+ | |||
+ | ===Arterial Thrombosis=== | ||
+ | |||
+ | * Although this is common in man, it is uncommon in domestic animals. | ||
+ | ** A major problem in man associated with atherosclerotic vascular disease. | ||
+ | * When they do occur in animals, arterial thrombi are usually small lesions. | ||
+ | ** However, these may be sited strategically, thereby causing problems. | ||
+ | |||
+ | ====Arteriosclerosis==== | ||
+ | |||
+ | * Seen in aged dogs and horses. | ||
+ | * Affect the coronary artery and other major arteries. | ||
+ | |||
+ | ====Verminous arteritis==== | ||
+ | |||
+ | * May occur with or without aneurysm. | ||
+ | * Seen in horses as a result of ''Strongylus vulgaris'' infestation. | ||
+ | ** Affects the root of cranial mesenteric artery, renal artery and aorta. | ||
+ | ** Results from larval migration in vessel walls. | ||
+ | |||
+ | ====Iliac thrombosis==== | ||
+ | |||
+ | * Seen in cats in the UK. | ||
+ | * Often referred to as "saddle embolus". | ||
+ | * Associated with cardio-myopathy and atrial thrombosis. | ||
+ | |||
+ | ===Cardiac Thrombosis=== | ||
+ | |||
+ | * Cardiac thrombosis is usually valvular, but can occasionally be mural. | ||
+ | |||
+ | ====Farm Species==== | ||
+ | |||
+ | * In farm animals, and rarely in the horse, infective/ inflammatory thrombosis occurs. | ||
+ | ** Known as endocarditis. | ||
+ | |||
+ | ====Dogs and Horse==== | ||
+ | |||
+ | * Cardiac thrombosis is generally of degenerative/ non-infectious cause. | ||
+ | ** Endocarditis may occur, though uncommonly. | ||
+ | * There are important effects of cardiac thrombosis. | ||
+ | *# Distortion of valve cusps leads to mechanical effects. | ||
+ | *#* Ineffective closeure gives leakage (incompetence). | ||
+ | *#* Distortion and enlargement of the valves by the thrombus mas fuves narrowing of the valve outflow (stenosis). | ||
+ | *#* These effects lead to progressive inefficiency of cardiac pumping. | ||
+ | *#** Causes [[Venous Congestion and Hyperaemia - Pathology#Generalised (Systemic) Venous Congestion|general venous congestion]], [[Oedema - Pathology|oedema]] and circulatory failure. | ||
+ | *# Emboli are disseminated from the thrombus mass. | ||
+ | *#* If the lesion is on the left side of the heart, emboli are disseminated systemically. | ||
+ | *#** Become trapped in the capilarry beds, e.g. of the kidney and spleen. | ||
+ | *#*** Blockage leads to local ischaemic necrosis. | ||
+ | *#* If the lesion is on the right side of the heart, there is pulmonary dissemination. | ||
+ | |||
+ | ====Atrial Thrombosis==== | ||
+ | |||
+ | * Uncommon. | ||
+ | ** Seen rarely in cats and dogs. | ||
+ | * Results from stasis in atrial appendages. | ||
+ | |||
+ | ===Venous Thrombosis=== | ||
+ | |||
+ | * Venous thrombosis is a fairly common type of thrombus in the veterinary species. | ||
+ | ** This is because: | ||
+ | **# Veins are relatively thin-walled. | ||
+ | **#* Are therefore more susceptible to distortion, inflammatory damage and iatrogenic vene puncture damage. | ||
+ | **# Veins have relatively slower blood flow rates. | ||
+ | **#* Cell aggregates tend 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. | ||
+ | ** Vene puncture damage. | ||
+ | |||
+ | ===Capillary Thrombosis=== | ||
+ | |||
+ | * These are microthrombi. | ||
+ | ** Only appreciable histologically. | ||
+ | * Formation may be: | ||
+ | ** Localised | ||
+ | *** Associated with acute local inflammation. | ||
+ | *** Not very significant unless strategically sited. | ||
+ | **Generalised | ||
+ | *** May be seen in terminal disease as a reflection of vascular failure. | ||
+ | *** Often associated with shock syndromes as part of [[Disseminated Intravascular Coagulation|disseminated intravascular coagulation]]. | ||
+ | *** Clinically very significant. | ||
+ | |||
+ | ==Evolution of a Thrombus== | ||
+ | |||
+ | * If the animal survives the immediate effects of a thrombus, the thrombus may evolve in one of the following ways: | ||
+ | # The thrombus may gradually '''enlarge''' and eventually cause total '''obstruction''' of a vessel. | ||
+ | # The thrombus may be completely '''removed by fibrinolytic activity'''. | ||
+ | #* Fibrinolysis is a very active process - clots are usually removed within a few days of formation. | ||
+ | #* Blood flow is crucial to the process of fibrinolysis. | ||
+ | #** An occlusive thrombus may prevent the necessary enzymes from reaching the clot. | ||
+ | #* To overcome occlusion, contraction of fresh clots under the influence of thrombasthenin (released by platelets) forms a slit-like channel beside the thrombus. | ||
+ | #** The blood that then flows past may completely dissolve the clot. | ||
+ | # '''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 quickly becomes covered by endothelium. | ||
+ | #** Is excluded from the clotting mechanism. | ||
+ | #* [[Neutrophils|Neutrophils]] invade the mass and may digest the centre. | ||
+ | #** Occasionally, subsequent invasion by bacteria may lead to 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 embolus'''. | ||
+ | |||
+ | |||
+ | [[Category:Arterial_Pathology]][[Category:Cardiovascular_System_-_Vascular_Pathology]][[Category:To_Do_-_Cardiovascular]] | ||
+ | [[Category:Venous_Pathology]] |
Revision as of 15:23, 1 July 2010
Thrombosis may be due to:
- Endothelial injury.
- Altered blood flow E.g. abnormal stasis.
- Hypercoagulability.
Often associated with other disease processes for example Disseminated intravascular coagulation.
Commonly see posterior paralysis of cats with cardiomyopathy.
Spontaneous venous thrombosis is rare. Seen in cattle with traumatic reticulo-peritonitis in the caudal vena cava.
Description
Thrombosis is a localized or generalized intravascular clot formation. Thrombi form as the result of trauma or pathological processes affecting the blood vessel endothelium or disturbances to blood flow and/or blood composition. Some diseases such as infective endocarditis and heart worm increase the risk of thrombi formation.
Diagnosis
History & Clinical Signs
- Signs depend on the area affected and the size of the blocked vessel.
- Poor perfusion below affected area.
- Malfunction and necrosis of affected organs
Laboratory Findings
Abnormalities associated with lack of blood perfusion and/or pathological conditions.
Ultrasonography
- Blood stasis
- Visualization of a thrombus
Angiography
- May show lack of opacity in affected region
Treatment
-Treat underlying problem
-IV Fluids
-Anticoagulant (Heparin for short term treatment, Aspirin for long term treatment)
Prognosis
-Depends on underlying condition
From general pathology
Introduction
- A thrombus is a solid blood clot that forms within the vessels or heart during life.
- The process of thrombus formation is known as thrombosis.
- Thrombii may occur anywhere within the cardiovascular system.
Thrombosis
- The process usually begins with platelets becoming sticky.
- Adhere to each other and to the endothelium.
- This increased "stickiness" is induced by contact with:
- Collagen
- Basement membrane
- Damaged endothelial cells
- Bacteria
Appearance of a Thrombus
- A thrombus is a layered mass which is attached to the vessel wall.
- The composition of a thrombus consists of red blood cells, [[Neutrophils - WikiBlood|neutrophils]] and platelets bound together by fibrin.
- Thrombi take different appareance 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.
- Tend to be pale and have a tail in the direction of blood flow.
- Venous thrombi
- Tend to be a darker red.
- The slow blood flow allows the clot to form quicker.
- Loosely arranged.
- Contains many red blood cells.
- Tend to be a darker red.
- Arterial thrombi
Causes of Thrombosis
- Thrombosis is caused by any condition that allows platelets to adhere to the endothelial wall.
Damage to the Vessel Wall
- When there is damage of the overlying endothelium, collagen is exposed and platelets will attach to this.
- The blood clotting process will occur, giving formation of an intraluminal blood clot.
- The process of formation occurs in phases giving a cross section of the clot a laminated appearance.
- The blood clotting process will occur, giving formation of an intraluminal blood clot.
- Vessel walls may be damaged in several ways:
- Trauma
- Localisation by colonies of bacteria
- Viral infection of endothelial cells
- Migration of parasites.
- Repeated puncture of the jugular vein is a common cause of serious or fatal thrombosis.
Changes in Normal Blood Flow
Stasis
- Stasis prevents coaglation factors being cleared by the liver and reticuloendothelial system.
- Coagulation factors build up, leading to clot formation.
- When stasis occurs in a vein, the thrombus forms behind the valve cusps.
- Quickly enlarges to fill the lumen.
Turbulence
- Turbulence disrupts the laminar flow.
- Platelets are brought into contact with the endothelial wall and may even damage the endothelium.
- Thrombi tend to form at arterial branches and venous junctions where there are eddy currents and local stasis.
Changes in Blood Composition
- An increase in the number and adhesiveness of platelets, or in plasma fibrin and clotting factors results in a hypercoagulateable state
- There may also be a decrease in the activity of the fibrinolyltic system.
- This may be caused by surgical or traumatic shock, or inflammation with toxaemia.
Types of Thrombosis
Arterial Thrombosis
- Although this is common in man, it is uncommon in domestic animals.
- A major problem in man associated with atherosclerotic vascular disease.
- When they do occur in animals, arterial thrombi are usually small lesions.
- However, these may be sited strategically, thereby causing problems.
Arteriosclerosis
- Seen in aged dogs and horses.
- Affect the coronary artery and other major arteries.
Verminous arteritis
- May occur with or without aneurysm.
- Seen in horses as a result of Strongylus vulgaris infestation.
- Affects the root of cranial mesenteric artery, renal artery and aorta.
- Results from larval migration in vessel walls.
Iliac thrombosis
- Seen in cats in the UK.
- Often referred to as "saddle embolus".
- Associated with cardio-myopathy and atrial thrombosis.
Cardiac Thrombosis
- Cardiac thrombosis is usually valvular, but can occasionally be mural.
Farm Species
- In farm animals, and rarely in the horse, infective/ inflammatory thrombosis occurs.
- Known as endocarditis.
Dogs and Horse
- Cardiac thrombosis is generally of degenerative/ non-infectious cause.
- Endocarditis may occur, though uncommonly.
- There are important effects of cardiac thrombosis.
- Distortion of valve cusps leads to mechanical effects.
- Ineffective closeure gives leakage (incompetence).
- Distortion and enlargement of the valves by the thrombus mas fuves narrowing of the valve outflow (stenosis).
- These effects lead to progressive inefficiency of cardiac pumping.
- Causes general venous congestion, oedema and circulatory failure.
- Emboli are disseminated from the thrombus mass.
- If the lesion is on the left side of the heart, emboli are disseminated systemically.
- Become trapped in the capilarry beds, e.g. of the kidney and spleen.
- Blockage leads to local ischaemic necrosis.
- Become trapped in the capilarry beds, e.g. of the kidney and spleen.
- If the lesion is on the right side of the heart, there is pulmonary dissemination.
- If the lesion is on the left side of the heart, emboli are disseminated systemically.
- Distortion of valve cusps leads to mechanical effects.
Atrial Thrombosis
- Uncommon.
- Seen rarely in cats and dogs.
- Results from stasis in atrial appendages.
Venous Thrombosis
- Venous thrombosis is a fairly common type of thrombus in the veterinary species.
- This is because:
- Veins are relatively thin-walled.
- Are therefore more susceptible to distortion, inflammatory damage and iatrogenic vene puncture damage.
- Veins have relatively slower blood flow rates.
- Cell aggregates tend to persist more readily.
- Veins are relatively thin-walled.
- This is because:
- Most venous thrombosis in domestic animals results from :
- Extension of inflammatory reactions.
- Erosion/disruption caused by malignant tumours.
- Pressure from adjacent space-occupying masses.
- Vene puncture damage.
Capillary Thrombosis
- These are microthrombi.
- Only appreciable histologically.
- Formation may be:
- Localised
- Associated with acute local inflammation.
- Not very significant unless strategically sited.
- Generalised
- May be seen in terminal disease as a reflection of vascular failure.
- Often associated with shock syndromes as part of disseminated intravascular coagulation.
- Clinically very significant.
- Localised
Evolution of a Thrombus
- If the animal survives the immediate effects of a thrombus, the thrombus may evolve in one of the following ways:
- The thrombus may gradually enlarge and eventually cause total obstruction of a vessel.
- The thrombus may be completely removed by fibrinolytic activity.
- Fibrinolysis is a very active process - clots are usually removed within a few days of formation.
- Blood flow is crucial to the process of fibrinolysis.
- An occlusive thrombus may prevent the necessary enzymes from reaching the clot.
- To overcome occlusion, contraction of fresh clots under the influence of thrombasthenin (released by platelets) forms a slit-like channel beside the thrombus.
- The blood that then flows past may completely dissolve the clot.
- 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 quickly becomes covered by endothelium.
- Is excluded from the clotting mechanism.
- Neutrophils invade the mass and may digest the centre.
- Occasionally, subsequent invasion by bacteria may lead to 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.
- Capillaries channels anastomose to produce vessels that traverse the thrombus and re-establish blood flow.
- A piece of the thrombus may break off and form an embolus.