A neuropsychiatric syndrome caused by acute or chronic hepatic insufficiency.
Symptoms vary in severity from a mild alteration in mental state to coma but are often reversible with treatment.
Causation is thought to be multi-factorial, resulting in brain exposure to ammonia that has bypassed the liver through portosystemic shunting.
Diagnosis is based on reported neurological deficits combined with laboratory abnormalities showing severe liver dysfunction.
Treatment approaches include providing supportive care (such as preventing aspiration), correcting precipitating factors, and reducing gastrointestinal production of ammonia.
Among patients with acute hepatic failure and severe encephalopathy, about 75% to 80% will develop cerebral oedema.
Hepatic encephalopathy (HE) encompasses a spectrum of neuropsychiatric abnormalities in patients with severe liver dysfunction. The World Congress of Gastroenterology suggests the following definitions: 
Persistent HE includes cognitive deficits, which negatively affect social and occupational functioning, and persistent non-cognitive abnormalities (such as extrapyramidal alterations or sleep disturbances).
Episodic HE corresponds to 'Delirium due to a General Medical Condition' in the DSM-5 classification system. Delirium is defined as 'a disturbance of consciousness that is accompanied by a change in cognition that cannot be better accounted for by a pre-existing or evolving dementia' that develops over a short period of time and fluctuates in severity.
Minimal HE comprises those patients who have no recognisable clinical symptoms of brain dysfunction. Therefore, the prerequisite for the diagnosis of minimal HE is the careful exclusion of clinical symptoms.
Affiliate Assistant Professor, Pulmonary and Critical Care Medicine
Department of Medicine
Oregon Health and Science University School of Medicine
ES declares that she has no competing interests.
Dr Emily Speelmon would like to gratefully acknowledge Dr Robert Hyzy and Dr Meilan Han, previous contributors to this monograph. MH and RH declare that they have no competing interests.
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