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- Reversible altered mental and neuromotor functioning occurring in association with acute or chronic liver disease and/or portal systemic shunting
- The prominent features are confusion, impaired arousability, and a “flapping tremor” (asterixis).
- System(s) affected: gastrointestinal (GI); nervous
- Synonym(s): portosystemic encephalopathy (PSE); hepatic coma; liver coma
Predominant sex: male = female (reflects prevalence of underlying liver disease)Prevalence
- Overt hepatic encephalopathy (HE) occurs in 30–45% of cirrhotic patients.
- Occurs in all cases of fulminant hepatic failure
- Present in ~50% of patients requiring liver transplantation
- Parallels the age predominance of fulminant liver disease: peaks in the 40s; cirrhosis peaks in the late 50s; may occur at any age
Etiology and Pathophysiology
- There is no defined pathophysiology for the development of HE. Three classifications have been proposed (1):
- Type A: resulting from acute liver failure
- Type B: resulting from portosystemic bypass or shunting
- Type C: resulting from cirrhosis
- Several metabolic factors implicated in HE based on the failure of the liver to detoxify noxious CNS agents (e.g., ammonia, mercaptan, fatty acids)
- Increased aromatic and reduced branched chain amino acids in blood may act as false neurotransmitters, possibly interacting with the γ-aminobutyric acid (GABA) receptor and causing clinical symptoms.
- HE presents most commonly in long-standing cirrhosis with spontaneous shunting of intestinal blood through collateral vessels or surgical portacaval shunts.
- Asterixis is the inability to maintain a particular posture due to metabolic encephalopathy. Abnormal diencephalic function leads to the characteristic liver flap noted when the arms and wrists are held in extension. Asterixis is also present in patients with uremia, barbiturate toxicity, and some cases of pulmonary disease. As such, asterixis is not pathognomonic for HE.
- Conditions that predispose an individual to developing chronic liver disease such as cystic fibrosis, α1-antitrypsin deficiency, hemochromatosis, and Wilson disease can contribute to the development of HE.
In patients with underlying liver disease, precipitating factors include:
- Infection (overt or occult, including spontaneous bacterial peritonitis [SBP])
- GI hemorrhage
- Use of sedative or opiate drugs
- Fluid or electrolyte disturbance (Na+, K+, Mg2+ most common)
- Transjugular intrahepatic portosystemic shunt (TIPS—a radiologically inserted shunt to lower portal pressure)—elderly patients and those with worse liver function are at increased risk of HE following TIPS
Commonly Associated Conditions
- May occur as a complication of acute fatty liver of pregnancy
- Occurs rarely in patients with a portacaval shunt but normal liver function