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| + | [[Hepatic Encephalopathy]] |
| − | ==Introduction==
| + | Pathology |
| − | '''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.
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| − | 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.
| + | **the horse may show very little visible neural changes, perhaps an increase in astrocytes |
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| − | ==Signalment==
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| − | No age, sex or breed predispositions.
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| − | There are many hepatic disorders which can lead to hepatic encephalopathy including, '''Hepatitis, [[Ragwort Toxicity]], [[Tyzzer's Disease]]''' and '''[[Hyperlipaemia - Horse|Hyperlipaemia]]'''
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| − | ==Diagnosis==
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| − | 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.
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| − | ===Clinical Signs===
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| − | Clinical signs vary depending on the severity of hepatic dysfunction, and may be associated with feeding.
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| − | Four clinical stages have been described for hepatic encephalopathy:
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| − | * Stage I: Mild changes in mentation; this stage is usually missed in horses.
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| − | * Stage II: Depressed mental state, lethargy, behavioural changes, head pressing, ataxia and 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.
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| − | Additional clinical signs associated with hepatic disease:
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| − | *Weight loss
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| − | *Diarrhoea
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| − | *Icterus
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| − | ===Laboratory Tests===
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| − | Haemotology and Biochemistry results will be consistent with hepatic disease; including increased GGT and SDH, [[Hypoalbuminaemia|hypoalbuminaemia]] and elevated [[Bile acids|bile acids]].
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| − | ===Biopsy===
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| − | A liver biopsy can provide a definitive diagnosis of liver disease; a clotting profile should be carried out before taking an ultrasound-guided biopsy.
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| − | ===Ultrasound===
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| − | Transabodimal ultrasound can be used to assess the structure of the liver and degree of damage.
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| − | ===Pathology===
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| − | See [[Hepatic Encephalopathy#Pathology|hepatic encephalopathy pathology]]
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| − | ==Treatment==
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| − | 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.
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| − | '''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.
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| − | 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.
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| − | Lactulose, mineral oil and neomycin or metronidazole can be administered in an attempt to reduce the production and absorption of hepatic toxins.
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| − | ==Prognosis==
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| − | Prognosis is '''poor''' to severe but depends on the underlying disease; signs are potentially reversible if the initiating course can be corrected.
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| − | 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.
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| − | {{Learning
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| − | |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]
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| − | ==References==
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| − | * Bertone, J. (2006) '''Equine Geriactric Medicine and Surgery''', ''Elsevier''
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| − | * Brown, C.M, Bertone, J.J. (2002) '''The 5-Minute Veterinary Consult- Equine'''', Lippincott, Williams & Wilkins''
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| − | * Knottenbelt, D.C. '''A Handbook of Equine Medicine for Final Year Students''' ''University of Liverpool''
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| − | * Mair, T., Love, S., Schumacher, J. and Watson, E. (1998) '''Equine Medicine, Surgery and Reproduction''' ''WB Saunders Company Ltd''
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| − | * Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''' ''Merial''
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| − | * Reed, S.M, Bayly, W.M, Sellon, D.C. (2004) '''Equine Internal Medicine''' (Second Edition) ''Saunders''.
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| − | * Rose, R. J. and Hodgson, D. R. (2000) '''Manual of Equine Practice''' (Second Edition) Sauders.
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| − | {{review}}
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| − | {{OpenPages}}
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| − | [[category:Expert_Review]]
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| − | [[Category:Liver Diseases - Horse]]
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| − | [[Category:Neurological Diseases - Horse]]
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