Acute liver failure is defined as "the rapid development of
hepatocellular dysfunction, specifically
coagulopathy and mental status changes (
encephalopathy) in a patient without known prior liver disease".:1557 The disease process is associated with the development of a coagulopathy of liver
aetiology, and clinically apparent altered level of consciousness due to
hepatic encephalopathy. Several important measures are immediately necessary when the patient presents for medical attention. The diagnosis of acute liver failure is based on a physical exam, laboratory findings, patient history, and past medical history to establish mental status changes, coagulopathy, rapidity of onset, and absence of known prior liver disease respectively. Another scheme defines "hyperacute" as onset within 7 days, "acute" as onset between 7 and 28 days, and "subacute" as onset between 28 days and 24 weeks.:1557 == Chronic ==