Hepatic steatosis

Nonalcoholic hepatic steatosis, or nonalcoholic fatty liver disease (NAFLD), is one of the most common causes of chronic liver disease in the developed world.

It is a spectrum of disease, ranging from hepatic fat accumulation without inflammation to steatohepatitis, fibrosis, cirrhosis, and end-stage liver disease.

NAFLD is considered the hepatic manifestation of metabolic syndrome and is associated with obesity, dyslipidemia, and type 2 diabetes mellitus.

The diagnosis of nonalcoholic fatty liver disease is based on exclusion of other etiologies of hepatic steatosis, such as alcohol use, and supportive laboratory tests and imaging. Liver biopsy and histology is the gold standard for diagnosis, and is performed for patients at higher risk of fibrosis or steatohepatitis.

Lifestyle modification, including weight loss, physical activity, and dietary changes, is the first-line therapy. There are no licensed drug treatments, although use of pioglitazone or vitamin E may be considered for selected patients.

Hepatic steatosis occurs when intrahepatic fat is ≥5% of liver weight.[1]Nassir F, Rector RS, Hammoud GM, et al. Pathogenesis and prevention of hepatic steatosis. Gastroenterol Hepatol (N Y). 2015 Mar;11(3):167-75. http://www.ncbi.nlm.nih.gov/pubmed/27099587?tool=bestpractice.com

Nonalcoholic fatty liver disease (NAFLD) is evidence of hepatic steatosis (imaging or histologic) in the absence of secondary causes of hepatic fat accumulation, such as significant alcohol consumption.[2]Chalasani N, Younossi Z, Lavine JE, et al. The diagnosis and management of nonalcoholic fatty liver disease: practice guidance from the American Association for the Study of Liver Diseases. Hepatology. 2018 Jan;67(1):328-57. https://www.doi.org/10.1002/hep.29367 http://www.ncbi.nlm.nih.gov/pubmed/28714183?tool=bestpractice.com

NAFLD can be categorized as nonalcoholic fatty liver (NAFL) or nonalcoholic steatohepatitis (NASH), depending on histologic features. NAFL is the presence of hepatic steatosis without evidence of hepatocellular injury in the form of hepatocyte ballooning. NASH is the presence of hepatic steatosis and inflammation with hepatocyte injury (e.g., ballooning), with or without fibrosis.[2]Chalasani N, Younossi Z, Lavine JE, et al. The diagnosis and management of nonalcoholic fatty liver disease: practice guidance from the American Association for the Study of Liver Diseases. Hepatology. 2018 Jan;67(1):328-57. https://www.doi.org/10.1002/hep.29367 http://www.ncbi.nlm.nih.gov/pubmed/28714183?tool=bestpractice.com This distinction is important for prognosis because NASH may progress to cirrhosis and liver failure. The risk of NAFL progressing to cirrhosis or liver failure is minimal.[2]Chalasani N, Younossi Z, Lavine JE, et al. The diagnosis and management of nonalcoholic fatty liver disease: practice guidance from the American Association for the Study of Liver Diseases. Hepatology. 2018 Jan;67(1):328-57. https://www.doi.org/10.1002/hep.29367 http://www.ncbi.nlm.nih.gov/pubmed/28714183?tool=bestpractice.com

To more accurately reflect the pathogenesis of fatty liver, a new nomenclature of metabolic associated fatty liver disease (MAFLD) has been suggested.[3]Eslam M, Sanyal AJ, George J, et al. MAFLD: a consensus-driven proposed nomenclature for metabolic associated fatty liver disease. Gastroenterology. 2020 May;158(7):1999-2014.e1. http://www.ncbi.nlm.nih.gov/pubmed/32044314?tool=bestpractice.com

This topic focuses on NAFLD. See also Alcoholic liver disease.