Hepatic encephalopathy: Part 1, a diagnostic approach

The first of this three-part review provides an overview of the clinical features, differential diagnoses and practical approach to the patient with hepatic encephalopathy (HE). HE is a debilitating condition seen in acute and chronic liver disease and/or portal-systemic shunting. Decades of research support the pathophysiological determination of a synergistic effect of gut-derived inflammation, infection and ammonia in its development. While HE is a distinct clinicopathological entity, patients with liver disease or portal hypertension remain vulnerable to other causes of altered mental state common in the general population. As there is no definitive test for overt HE, diagnosis relies on exclusion of differential diagnoses, considering several treatable conditions. We propose a four-step approach for identifying HE in patients presenting to the emergency department or outpatient clinics: (1) defining the underlying disease, (2) clinical characterisation, (3) identifying precipitants and risk factors and (4) excluding alternative diagnoses. Additionally, we will discuss the use of neuropsychological and neurophysiological testing for the diagnosis of covert HE. The second instalment of this review series will cover the investigation and management of HE in acute and acute-on-chronic liver failure, and the third instalment will cover outpatient management of HE.