Nonalcoholic fatty liver disease and NASH: Clinical and histological aspects

Paralleling the increasing prevalence of obesity, diabetes mellitus, and the metabolic syndrome in the general population, nonalcoholic fatty liver disease (NAFLD) has become the most common cause of chronic liver disease worldwide. The diagnosis of NAFLD is established based on evidence of fatty infiltration of the liver in the absence of excessive alcohol ingestion. NAFLD is often diagnosed in asymptomatic persons after the detection of raised aminotransferase during routine screening or evidence of steatosis on ultrasonography. The spectrum of liver injury is variable ranging from simple steatosis with benign prognosis, to nonalcoholic steatohepatitis (NASH) and cirrhosis, conferring an increase in liver-related morbidity and mortality. More advanced stages of NAFLD are associated with older age, higher body mass index, diabetes, hypertension, high triglycerides, and/or insulin resistance. No imaging modality can distinguish NASH from simple steatosis. Liver biopsy remains the only reliable means to determine prognosis based on the severity of fibrosis. The system for histological evaluation for NAFLD/NASH has been proposed by several groups based on a constellation of histologic features rather than any individual feature. The different semiquantitative scoring system for NAFLD/NASH has been used in clinical trials and natural history studies of NAFLD.