Non-alcoholic fatty liver disease (NAFLD) affects over 25% of the world’s population, and is projected to be a leading cause of chronic liver disease by 2020. The projected annual economic impact of NAFLD is estimated at $292 billion in the United States annually. First described in 1980, NAFLD is characterized by excessive fat deposition in the liver, in the absence of other causes of liver disease, including inordinate consumption of alcohol. The growing epidemic of obesity along with other components of metabolic syndrome are responsible for disease prevalence.
The disease spectrum of NAFLD ranges from non-alcoholic fatty liver (NAFL)—characterized by fat in at least 5% of hepatocytes without inflammation—to non-alcoholic steatohepatitis (NASH)—characterized by 5% hepatic steatosis with lobular inflammation, ballooning, and acidophilic degeneration of hepatocytes with or without fibrosis—to cirrhosis and hepatocellular carcinoma (HCC). NASH carries a much higher risk for progression to cirrhosis compared with NAFL and is rapidly rising as an etiology of end-stage liver disease. It is the second leading indication for liver transplantation in the United States behind hepatitis C virus infection and will likely become the number one indication for transplantation in the future. It also is the fastest growing indication for simultaneous liver–kidney transplantation.9 In long-term follow-up, NAFLD has been shown to be a major problem among liver transplant recipients. In addition, the rising incidence of obesity has led to a dramatic rise in NAFLD-related HCC, at an annual rate of 9%.