Non-alcoholic fatty liver: a common manifestation of a metabolic disorder.

Non-alcoholic fatty liver (NAFL) is one of the most common liver diseases encountered in the United States and Europe. This term refers to a spectrum of hepatic pathology that resembles alcoholic liver disease, but appears in individuals who have low or negligible alcohol consumption. Initially the term non-alcoholic steatohepatitis (NASH) was employed by Ludwig et al. in 1980 to describe a syndrome in morbidly obese females with type 2 diabetes mellitus (DM), in whom the hepatic histology was consistent with alcoholic hepatitis, but there was no history of alcohol use. More recently it has become apparent that NAFL is a spectrum of disease (Table 1). It has been suggested that the term NASH should be used only for the more severe forms of NAFL that correspond to types 3 and 4 with alcoholic-like histological findings. As in alcoholic liver disease, steatosis in NAFL is predominantly macrovesicular and generally distributed diffusely throughout the liver lobule, although prominent microvesicular steatosis or zone 3 (perivenular) steatosis is occasionally found. NAFL is now thought to be the commonest cause of abnormal liver enzymes encountered in general practice, and to result in cirrhosis in a significant proportion of the patients. We review the current evidence on the prevalence, natural history and treatment of NAFL, limiting the discussion to primary NAFL. Many medications, acute and chronic illnesses can produce steatosis and steatohepatitis, but these are beyond the scope of this review.