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| HE may be precipitated by severel conditions in animals, all of which cause an increase in the blood concentrations of ammonia and/or mercaptans: | | HE may be precipitated by severel conditions in animals, all of which cause an increase in the blood concentrations of ammonia and/or mercaptans: |
− | *'''Metabolic alkalosis''' | + | *'''Metabolic alkalosis''' increases the production of ammonia by the kidneys and increases the uptake of urea across the blood brain barrier. |
| *'''Hypokalaemia''' | | *'''Hypokalaemia''' |
| *'''Constipation''', increasing the length of time that colonic bacteria are able to act on undigested amino acids. | | *'''Constipation''', increasing the length of time that colonic bacteria are able to act on undigested amino acids. |
| *'''Gastro-intestinal haemorrhage''', increasing the amount of protein available to GI bacteria. | | *'''Gastro-intestinal haemorrhage''', increasing the amount of protein available to GI bacteria. |
| *'''Diet with a high protein, purine or methionine content''' | | *'''Diet with a high protein, purine or methionine content''' |
− | *'''Azotaemia''' | + | *'''Azotaemia''', increasing the concentration of urea in the GI tract and also causing GI haemorrhage if [[Uraemia|uraemia]] develops. |
− | *'''Hypermetabolic state or fever''', as may occur in many forms of systemic illness due to the effects of inflammatory cytokines and which leads to the catabolism of lean body protein. | + | *'''Hypermetabolic state or fever''', as may occur in many forms of systemic illness due to the effects of inflammatory cytokines and which leads to the catabolism of lean body protein. A similar phenemenon may occur if glucocorticoids are administered at high doses. |
| *'''Dehydration''' increases the effective circulating ammonia concentraton. | | *'''Dehydration''' increases the effective circulating ammonia concentraton. |
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| ===Diagnostic Imaging=== | | ===Diagnostic Imaging=== |
| Imaging is not required to make a diagnosis of HE but it may reveal abnormalities relating to the underlying cause. | | Imaging is not required to make a diagnosis of HE but it may reveal abnormalities relating to the underlying cause. |
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| + | ==Pathology== |
| + | Myelin degeneration, consisting of vacuoles between the grey and white matter, may be observed on histopathological examination of cerebral tissues from affected animals. |
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| ==Treatment== | | ==Treatment== |
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− | ==From Pathology==
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− | ===Clinical===
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− | *non-specific neurological signs (attributed to the retention of ammonia and gamma aminobutyric acid in [[Liver - Anatomy & Physiology|liver]] failure and their effects on the brain)
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− | **dullness
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− | **apparent unawareness of surroundings
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− | **pointless or compulsive movements
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− | **mania
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− | **generalised convulsions
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− | NB: usually soon followed by death
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− | ===Microscopically===
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− | *lesions in the brain vary in expression
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− | **most species may show myelin degeneration consisting of vacuoles between the grey and white matter
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− | **the horse may show very little visible neural changes, perhaps an increase in astrocytes
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− | ===Causes===
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− | ::[[Portosystemic Shunt|Portosystemic Shunting]]
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− |
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− | ::Chronic [[Liver - Anatomy & Physiology|liver]] damage
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− | *due to ingestion of toxic compounds over a long period of time
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− | *E.g. [[Ragwort|ragwort]] [[Category:Liver_-_General_Pathology]]
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| + | [[Category:Liver_-_General_Pathology]] |
| [[Category:Dog]][[Category:Cat]] | | [[Category:Dog]][[Category:Cat]] |
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| [[Category:To_Do_-_James]] | | [[Category:To_Do_-_James]] |