Overview: an introduction to NASH and related fatty liver disorders

This chapter introduces the history, definitional and semantic issues, spectrum and general importance of non-alcoholic fatty liver diseases (NAFLD). Nonalcoholic steatohepatitis (NASH) is a form of metabolic liver disease in which fatty change (steatosis) is associated with lobular inflammation, hepatocyte injury and/or hepatic fibrosis. It comprises a pathogenic link in the chain of NAFLD that extends from bland steatosis to some cases of ‘cryptogenic cirrhosis’. NAFLD and NASH are usually hepatic manifestations of the insulin resistance (or metabolic) syndrome (syndrome X), but the factors that transform steatosis to NASH remain unclear. NAFLD/NASH is the most common type of liver disease in affluent societies, affecting between 2 and 8% of the population. NASH typically causes no symptoms. When present, clinical features such as fatigue, hepatomegaly and aching hepatic discomfort are non-specific. In 20–25% of cases, NASH may progress to advanced stages of hepatic fibrosis and cirrhosis; liver failure then becomes the most common cause of death, and hepatocellular carcinoma (HCC) may occasionally occur. Correction of insulin resistance by dietary measures and increased physical activity (lifestyle intervention) is a logical approach to prevent or reverse early NASH, and modest weight reduction can normalize liver test abnormalities. Drug therapy aimed at reversing insulin resistance, correcting diabetes and lipid disorders, or Overview: an introduction to NASH and related fatty liver disorders