Epidemiology and natural history of NAFLD and NASH.

Understanding of the epidemiology and natural history of non-alcoholic fatty liver disease (NAFLD) has increased; it is the most common form of chronic liver disease in the Western world and increasing in importance in other parts of the world. Prevalence is expected to increase as obesity and diabetes epidemics evolve. The natural history of NAFLD depends on the histologic subtype. Those who have simple hepatic steatosis or nonspecific inflammation generally have a benign long-term prognosis, whereas non-alcoholic steatohepatitis (NASH) can progress to cirrhosis. NASH-related cirrhosis may have a similar prognosis as cirrhosis from other causes, leading to liver failure or hepatocellular carcinoma.