The goal of initial laboratory evaluation is to find the potential causes of FHF, as well as to evaluate other organ system function. On arrival, the patient should have a complete blood count, platelet count, chemistries, liver function tests (albumin, bilirubin, alkaline phosphatase, AST, and ALT), prothrombin time (INR), arterial blood gas, factor V level, blood glucose level, and ammonia level. The preceding tests should be performed on a scheduled basis because clinical deterioration may be swift and unpredictable. Possible causes of FHF are sought through serologic assays for hepatitis A (anti-HAV IgM) and hepatitis B (anti-HBV IgM, HBsAg, HBcAb) and serum assays for ceruloplasmin, iron-binding capacity, toxic substances, and acetaminophen. A right upper quadrant ultrasound is useful in providing information regarding the patency of the hepatic vessels, liver size, presence of acites, and degree of compression of the porta hepatitis by intraabdominal masses. The role for liver biopsy is controversial. Although transjugular liver biopsies can be performed safely, there is little correlation between the extent of hepatic necrosis and the recoverability of the liver likely owing to sampling error. Despite this, liver biopsies are useful in patients for whom the cause of FHF is uncertain, or when lymphoma is a possible cause.