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==Description==
==Introduction==
'''Hepatic encephalopathy''' is neurological disfunction caused by any acute or severe hepatic damage; 60-80% of hepatic function must be lost before clinical signs develop. A combination of the following mechanisms are probably responsible for the syndrome, hepatic insufficiency allows the build up of ammonia which affects neurotransmission in the CNS, toxic metabolites may act as false neurotransmitters and there can be an imblance between excitatory and inhibitory neurotransmission.
'''Hepatic encephalopathy''' is neurological dysfunction caused by any acute or severe hepatic damage; 60-80% of hepatic function must be lost before clinical signs develop.
The cause of hepatic encephalopathy is hepatic insufficiency; the pathophysiology causing the neurological dysfunction is probably multifactorial. The following mechanisms have been suggested: accumulation of gastro-intestinal derived neurotoxins, imbalance of inhibitory and excitatory neurotransmitters, disruption of CNS energy metabolism, and the development of false neurotransmitters.
==Signalment==
==Signalment==
No age, sex or breed predisposions.
No age, sex or breed predispositions.
There are many hepatic disorders which can lead to hepatic encephalopathy including, '''[[Hepatitis, Equine Serum|Hepatitis]], [[Ragwort Toxicity]], [[Tyzzer's Disease]]''' and '''[[Hyperlipaemia - Horse|Hyperlipaemia]]'''
There are many hepatic disorders which can lead to hepatic encephalopathy including, '''Hepatitis, [[Ragwort Toxicity]], [[Tyzzer's Disease]]''' and '''[[Hyperlipaemia - Horse|Hyperlipaemia]]'''
==Diagnosis==
==Diagnosis==
Diagnosis is made on clinical signs of cerebral dysfunction with evidence of hepatic insufficiency, in the absence of other potential causes for the neurological signs.
===Clinical Signs===
===Clinical Signs===
Clinical signs vary depending on the severity of hepatic dysfunction, early signs are often subtle and may be missed. Clinical signs may be associated with feeding.
Clinical signs vary depending on the severity of hepatic dysfunction, and may be associated with feeding.
Four clinical stages have been described for hepatic encephalopathy:
*Lethargy
* Stage I: Mild changes in mentation; this stage is usually missed in horses.
*Head pressing
* Stage II: Depressed mental state, lethargy, behavioural changes, head pressing, ataxia and dysphagia.
*Dysphagia
* Stage III: Somnolent but rousable. Reactions may be very reduced or exaggerated.
* Stage IV: Coma, Seizures are rare but may occur in the late stages of the condition.
*Seizures
Additional clinical signs associated with hepatic disease:
*Weight loss
*Weight loss
*Diarrhoea
*Diarrhoea
===Biopsy===
===Biopsy===
A liver biopsy can provide a definitive diagnosis of liver disease, a clotting profile should be carried out before taking an ultrasound-guided biopsy.
A liver biopsy can provide a definitive diagnosis of liver disease; a clotting profile should be carried out before taking an ultrasound-guided biopsy.
===Ultrasound===
===Ultrasound===
===Pathology===
===Pathology===
See [[Hepatic Encephalopathy]] Pathology
See [[Hepatic Encephalopathy#Pathology|hepatic encephalopathy pathology]]
==Treatment==
==Treatment==
With supportive therapy horses may recover from hepatic encephalopathy after 4-21 days. Treatment is only warranted in acute cases likely to make a recovery.
With '''supportive''' therapy horses may recover from hepatic encephalopathy after 4-21 days. Treatment is only warranted in acute cases likely to make a recovery.
'''Sedation''' is often necessary in cases of hepatic encephalopathy; An alpha 2 agonist at a low dose is usually effective. If the neurological signs are so severe that the horse is a danger to itself and others then immediate '''euthansia''' is indicated.
'''Sedation''' is often necessary in cases of hepatic encephalopathy; An alpha 2 agonist at a low dose is usually effective. If the neurological signs are so severe that the horse is a danger to itself and others then '''euthanasia''' may be indicated.
Fluid deficits and acid base abnormalities should be corrected as necessary and hypoglycaemic animals should be given a 5% dextrose solution IV. High carbohydrate, low protein diets should be fed in small amounts fequently.
Fluid deficits and acid base abnormalities should be corrected as necessary and hypoglycaemic animals should be given a 5% dextrose solution IV. High carbohydrate, low protein diets should be fed in small amounts and frequently.
Lactulose, mineral oil and neomycin or metronidazole can be administered in an attempt to reduce the production and absorption of hepatic toxins.
==Prognosis==
==Prognosis==
Prognosis is '''poor''' to severe but depend on the underlying disease; signs are potentially reversible if the initiating course can be corrected.
Prognosis is '''poor''' to severe but depends on the underlying disease; signs are potentially reversible if the initiating course can be corrected.
Horses with hepatic disease showing neurological signs have a poorer prognosis than those showing only signs af hepatic dysfunction. However with appropriate supportive therapy 40% of horses survive for at least 6 months. Recovery may be incomplete and temporary.
Horses with hepatic disease showing neurological signs have a poorer prognosis than those showing only signs of hepatic dysfunction. However with appropriate supportive therapy 40% of horses survive for at least 6 months. Recovery may be incomplete and temporary.
{{Learning
|literature search = [http://www.cabdirect.org/search.html?q=%28title%3A%28Hepatic%29+OR+title%3A%28liver%29+OR+title%3A%28Portosystemic%29%29+AND+%28title%3A%28Encephalopathy%29+OR+title%3A%28coma%29%29+AND+od%3A%28horses%29 Hepatic Encephalopathy in horses publications]
}}
==References==
==References==
* Bertone, J. (2006) '''Equine Geriactric Medicine and Surgery''', ''Elsevier''
* Bertone, J. (2006) '''Equine Geriactric Medicine and Surgery''', ''Elsevier''
* Brown, C.M, Bertone, J.J. (2002) '''The 5-Minute Veterinary Consult- Equine'''', Lippincott, Williams & Wilkins''
* Knottenbelt, D.C. '''A Handbook of Equine Medicine for Final Year Students''' ''University of Liverpool''
* Knottenbelt, D.C. '''A Handbook of Equine Medicine for Final Year Students''' ''University of Liverpool''
* Mair, T., Love, S., Schumacher, J. and Watson, E. (1998) '''Equine Medicine, Surgery and Reproduction''' ''WB Saunders Company Ltd''
* Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''' ''Merial''
* Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''' ''Merial''
* Reed, S.M, Bayly, W.M, Sellon, D.C. (2004) '''Equine Internal Medicine''' (Second Edition) ''Saunders''.
* Rose, R. J. and Hodgson, D. R. (2000) '''Manual of Equine Practice''' (Second Edition) Sauders.
* Rose, R. J. and Hodgson, D. R. (2000) '''Manual of Equine Practice''' (Second Edition) Sauders.
[[Category:To_Do_-_lizzyk]]
[[Category:Liver_Disorders_-_Horse]]
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[[Category:Neurological_Disorders_-_Horse]]
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[[Category:Liver Diseases - Horse]]
[[Category:Neurological Diseases - Horse]]