Pathology of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) may be the most common cause of chronic liver disease in Western countries, with an estimated prevalence of up to 24% in the general population. NAFLD is considered the hepatic manifestation of the metabolic syndrome and has been etiologically correlated with insulin resistance. The histopathological spectrum of NAFLD ranges from simple steatosis to nonalcoholic steatohepatitis (NASH), with or without fibrosis, and cirrhosis. Liver biopsy is the "gold standard" for diagnosing NASH in a patient with clinical features of NAFLD, image detected steatosis and chronically elevated liver enzymes. This review discusses the histopathological findings of NAFLD in adults and children, including features representing resolution of NASH following treatment and features of prognostic information. Additionally, current systems of semiquantitative assessment in NAFLD and NASH are reviewed and the concurrence of NAFLD and NASH with other chronic liver diseases, mainly hepatitis C, is discussed.