Equis ISSN 2398-2977

Liver: hepatoencephalopathy

Contributor(s): Frank Andrews, Debbie Deem Morris, Caroline Hahn, Imogen Johns, Robert J MacKay, Vetstream Ltd

Introduction

  • Syndrome characterized by abnormal mentation due to protein and other metabolites crossing the blood-brain barrier in severe hepatic dysfunction and leading to diffuse cerebral impairment.
  • Cause: severe hepatic insufficiency; course may be acute, eg Theilers, or chronic, eg ragwort poisoning, Crotalaria spp; rarely portosystemic shunts.
  • Signs: abnormal mentation, from depression, dementia   →   coma.
  • Diagnosis: history and clinical signs suggestive; confirmation is by presence of laboratory findings indicative of liver failure.
  • Treatment: supportive.
  • Prognosis: very poor - hepatic damage is usually irreversible.
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Pathogenesis

Etiology

Pathophysiology

  • Incompletely understood.
  • Multiple theories - systemic ammonia accumulation secondary to liver dysfunction occurs. Ammonia accumulates in the brain, acting as a neurotoxin.
  • Other theories - alteration in amino acid metabolism due to liver dysfunction results in imbalance between aromatic amino acids (AAA) and branched chain amino acids (BCAA) AAA preferentially cross blood brain barrier and act as precursor for serotonin, an inhibitory neurotransmitter.
  • End result is diffuse cerebral impairment.
  • Hepatic dysfunction   →   systemic accumulation of metabolic byproducts, eg ammonia that   →    an imbalance of fatty acids and excitatory and inhibitory neurotransmitters such as gamma amino butyric acid (GABA) or glutamate   →   cross permeability-altered blood-brain barrier   →   diffuse cerebral impairment.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Oliveira-Filho J Pet al(2013)Hepatoencephalopathy syndrome due toCassia occidentalis(Leguminosae, Caesalpinioideae) seed ingestion in horses.Equine Vet J45(2), 240-244 PubMed.
  • Muller J M Vet al(2011)Ataxia and weakness as uncommon primary manifestations of hepatic encephalopathy in a 15-year-old trotter gelding.Equine Vet Educ23(1), 5-10 VetMedResource.
  • Nout Y S (2011)Gait deficits in liver disease: Hepatic encephalopathy and hepatic myelopathy.Equine Vet Educ23(1), 11-13 VetMedResource.
  • Hughes K J, McGorum B C, Love S & Dixon P M (2009)Bilateral laryngeal paralysis associated with hepatic dysfunction and hepatic encephalopathy in six ponies and four horses.Vet Rec164(5), 142-147 PubMed.
  • Johns I C, del Piero F & Wilkins P A (2009)Hepatic encephalopathy in a pregnant mare: identification of histopathological changes in the brain of a mare and fetus.Aust Vet J85, 337-340 PubMed.


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