Non-alcoholic fatty liver disease: epidemiology, clinical course, investigation, and treatment

The global obesity epidemic has increased the prevalence of fatty liver disease. At present, 14% to 27% of the general population in the industrialized world has non-alcoholic fatty liver disease (NAFLD).

We review pertinent publications retrieved by a selective search of the PubMed database for the years 1995 to 2013.

The term "non-alcoholic fatty liver disease" covers cases of a wide spectrum of severity, ranging from bland fatty liver without any inflammation and with little or no tendency to progress all the way to non-alcoholic steato-hepatitis (NASH) with inflammatory reactions and hepatocyte damage, with or without fibrosis. Some 5% to 20% of patients with NAFLD develop NASH, which undergoes a further transition to higher-grade fibrosis in 10% to 20% of cases. In fewer than 5% of cases, fibrosis progresses to cirrhosis. These approximate figures lead to an estimate of 0.05% to 0.3% for the prevalence of cirrhosis in the general population. About 2% of all cirrhosis patients per year develop hepatocellular carcinoma. The diagnosis of fatty liver disease can be suspected initially on the basis of abnormally high aspartate aminotransferase (ASAT) and/or alanine aminotransferase (ALAT) levels and abnormal ultrasonographic findings. The positive predictive value of an ultrasonographic study for mild steatosis is 67% at most. The NAFLD fibrosis score, which is computed on the basis of multiple parameters (age, body-mass index, diabetes status, ASAT, ALAT, platelet count, and albumin level), has a positive predictive value of 82% to 90% and a negative predictive value of 88% to 93%. Liver biopsy is the gold standard for diagnosis but should be performed sparingly in view of its rare but sometimes life-threatening complications, such as hemorrhage. The treatment of NAFLD and NASH consists mainly of changes in lifestyle and nutrition.

NAFLD can, in principle, be reversed. This is only possible with weight reduction by at least 3% to 5%.