DEFINITION

• Nonalcoholic fatty liver disease (NAFLD): encompasses the entire spectrum of fatty liver disease, ranging from fatty liver to steatohepatitis to cirrhosis[11][1]
  • By definition, requires exclusion of significant alcohol consumption. Definition of significant levels of alcohol consumption is controversial but in general > 21 standard drinks/week in men and > 14 standard drinks/week in women are considered the threshold, with a standard alcoholic drink defined as a drink containing 14 g of alcohol.
  • Nonalcoholic fatty liver: fatty infiltration (steatosis) of the liver, exceeding 5% of liver weight. In biopsy specimens, >5-10% macrosteatotic hepatocytes.
  • Primary NAFLD: common term for typical NAFLD associated with obesity and/or type 2 diabetes (T2DM) or insulin resistance (IR), without another specific etiology.
  • Secondary NAFLD: defined as NAFLD in the absence of insulin resistance and associated with other causes such as: polycystic ovary syndrome, hypothyroidism, hypogonadism, hypopituitarism, medication use (glucocorticoids, tamoxifen, amiodarone, HAART, diltiazem), disorders of lipid metabolism (abetalipoproteinemia, lipodystrophy, Weber-Christian syndrome, Andersen’s disease), total parenteral nutrition and jejunoileal bypass surgery. Many cases of "secondary" NAFLD likely represent an exacerbation of often unrecognized "primary" NAFLD.
  • Nonalcoholic steatohepatitis (NASH): the more severe form of NAFLD characterized by inflammation, hepatocyte injury (ballooned hepatocytes), with or without fibrosis. It can progress to cirrhosis and possibly liver cancer.
  • NASH cirrhosis: the presence of cirrhosis with current or previous evidence of steatosis or NASH.
  • Cryptogenic cirrhosis: presence of cirrhosis with no obvious etiology; however, frequently this is attributed to NAFLD, especially if there is a history of diabetes and obesity.[25][27]