Acute Hepatic Failure

Acute liver failure is a clinical syndrome resulting from massive necrosis of hepatocytes or from severe functional impairment of hepatocytes. The synthetic, excretory, and detoxifying functions of the liver are all severely impaired. In adults, hepatic encephalopathy has been an essential diagnostic feature. However, in pediatrics, this narrow definition may be problematic, as early hepatic encephalopathy can be difficult to detect in infants and children, and some children in acute liver failure may not develop encephalopathy. The accepted definition in children includes biochemical evidence of acute liver injury (usually <8 wk duration); no evidence of chronic liver disease; and hepatic-based coagulopathy defined as a prothrombin time (PT) >15 sec or international normalized ratio (INR) >1.5 not corrected by vitamin K in the presence of clinical hepatic encephalopathy, or a PT >20 sec or INR >2 regardless of the presence of clinical hepatic encephalopathy.

Liver failure in the perinatal period can be associated with prenatal liver injury and even cirrhosis. Examples include gestational alloimmune liver disease (GALD), tyrosinemia, familial hemophagocytic lymphohistiocytosis (HLH), and some cases of congenital viral (herpes simplex virus [HSV]) infection. Liver disease may be noticed at birth or after several days of apparent well-being. Fulminant Wilson disease and fulminant autoimmune hepatitis also occurs in older children who were previously asymptomatic but, by definition, have preexisting liver disease. Other forms of acute-on-chronic liver failure can occur when a patient with an underlying liver disease such as biliary atresia develops hepatic decompensation after viral or drug-induced hepatic injury. In some cases of liver failure, particularly in the idiopathic form of acute hepatic failure, the onset of encephalopathy occurs later, from 8 to 28 wk after the onset of jaundice.