Changes

==Description==

==Description==

Platelets (or thrombocytes) are responsible for primary haemostasis, the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall.  Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia''').  Thrombocytopaenia may be a '''primary disease''' due to disease of the bone marrow that reduces the production of platelets or it may occur '''secondary''' to another insult.  '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.

[[Platelet|Platelets]] (or thrombocytes) are responsible for primary haemostasis, the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall.  Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia''').  Thrombocytopaenia may be a '''primary disease''', relating to a failure to produce platelets in the bone marrow, or it may occur '''secondary''' to another insult.  '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.

==Thrombocytopaenia==

==Thrombocytopaenia==

===Primary Thrombocytopaenic Disease===

===Primary Thrombocytopaenic Disease===

The aetiology of primary thrombocytopenic disease is often uncertain and it is therefore also known as '''idiopathic''' thrombocytopaenia.  Some cases of primary thrombocytopaenia may occur due to autoimmune responses directed at platelets and, although the [[Bone Marrow - Anatomy & Physiology|bone marrow]] may contain adequate normal megakaryocytes, this disease results in a reduced peripheral blood thrombocyte count.  [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] occurs most commonly in young animals.

The aetiology of primary thrombocytopenic disease is often uncertain and it is therefore also known as '''idiopathic''' thrombocytopaenia.  Some cases of primary thrombocytopaenia may occur due to autoimmune responses directed at platelets and, although the [[Bone Marrow - Anatomy & Physiology|bone marrow]] may contain adequate numbers of normal megakaryocytes, this disease results in a reduced peripheral blood thrombocyte count.  [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] occurs most commonly in young animals.

===Secondary Thrombocytopaenic Disease===

===Secondary Thrombocytopaenic Disease===

**'''Radiotherapy''' or myelosuppressive '''chemotherapy''' may cause reversible bone marrow suppression.

**'''Radiotherapy''' or myelosuppressive '''chemotherapy''' may cause reversible bone marrow suppression.

*Diseases that cause '''increased destruction of platelets'''

*Diseases that cause '''increased destruction of platelets'''

**'''Infectious diseases''' that cause destruction of platelets, including [[Bovine Viral Diarrhoea Virus|bovine viral diarrhoea]], [[Classical Swine Fever|classical swine fever]] and [[Infectious Canine Hepatitis|infectious canine hepatitis]].  The parasites ''[[Ehrlichia platys]]'', ''[[Anaplasma phagocytophilum]]'' and ''[[Ehrlichia canis]]'' may also cause infectious thrombocytopaenia.  Any severe bacterial infection, including those caused by [[:Category:Staphylococcus species|''Staphylococci'']] and the Gram negative bacteria that produce endotoxin (e.g. [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas spp.'']] or [[Salmonella|''Salmonella spp.'']]) may also result in the destruction of platelets.

**'''Infectious diseases''' that cause destruction of platelets include [[Bovine Viral Diarrhoea Virus|bovine viral diarrhoea]], [[Classical Swine Fever|classical swine fever]] and [[Infectious Canine Hepatitis|infectious canine hepatitis]].  The parasites ''[[Ehrlichia platys]]'', ''[[Anaplasma phagocytophilum]]'' and ''[[Ehrlichia canis]]'' may also cause infectious thrombocytopaenia.  Any severe bacterial infection, including those caused by [[:Category:Staphylococcus species|''Staphylococci'']] and the Gram negative bacteria that produce endotoxin (e.g. [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas spp.'']] or [[Salmonella|''Salmonella spp.'']]) may also result in the destruction of platelets.

*Diseases that cause '''sequestration of platelets''' usually involve some enlargement to the spleen as this is the major organ where platelets are stored outside of the circulation.  Examples include:

*Diseases that cause '''sequestration of platelets''' usually involve some enlargement of the spleen as this is the major organ where platelets are stored outside of the circulation.  Examples include:

**[[Haemangiosarcoma]] of the spleen and liver

**[[Haemangiosarcoma]] of the spleen and liver

**Splenic enlargement under general anaesthesia maintained with agents such as [[Barbiturates|barbiturates]] and [[Phenothiazines|phenothiazines]]

**Splenic enlargement under general anaesthesia maintained with agents such as [[Barbiturates|barbiturates]] and [[Phenothiazines|phenothiazines]]