What is ALF (Acute Liver Failure)?
ALF is a rare but life-threatening condition defined by coagulation abnormality (INR ≥1.5) and any degree of mental alteration (encephalopathy) in a patient without preexisting cirrhosis, with illness duration ≤26 weeks. 1
Core Diagnostic Criteria
The diagnosis requires three essential components 1:
- Coagulation abnormality: Prothrombin time prolonged by 4-6 seconds or more, resulting in INR ≥1.5
- Altered mental status: Any degree of encephalopathy, from subtle changes to coma
- Absence of cirrhosis: No preexisting chronic liver disease (with exceptions for Wilson disease, vertically-acquired HBV, or autoimmune hepatitis if recognized for ≤26 weeks)
- Time frame: Illness duration of 26 weeks or less
Immediate Clinical Action
Hospital admission is mandatory once ALF is diagnosed, with early ICU transfer preferred since consciousness can deteriorate hour-by-hour. 1
All patients with moderate to severe acute hepatitis require immediate measurement of prothrombin time and careful evaluation for subtle mental status changes 1. The condition progresses rapidly, making early recognition critical for survival.
Terminology Clarification
The term "acute liver failure" is preferred over older terms like "fulminant hepatic failure" or "fulminant hepatitis" 1. Subcategories based on illness duration (hyperacute: ≤7 days; acute: 7-21 days; subacute: 21 days to 26 weeks) lack independent prognostic significance beyond the underlying cause 1. For example, hyperacute cases may have better prognosis primarily because most result from acetaminophen toxicity, not because of the timeframe itself.
Clinical Outcomes and Prognosis
ALF carries high morbidity and mortality 1. Liver transplantation represents the definitive treatment for some patients, requiring significant resources and lifetime immunosuppression, while other patients experience spontaneous resolution without long-term sequelae 1.
Common Pitfall to Avoid
Do not confuse ALF (Acute Liver Failure) with ACLF (Acute-on-Chronic Liver Failure). 1 ACLF occurs in patients with preexisting cirrhosis who develop acute decompensation with organ failures, whereas ALF specifically excludes patients with cirrhosis (except the three specific conditions noted above). The diagnostic criteria, management approaches, and prognostic scoring systems differ substantially between these two conditions.