Non-alcoholic fatty liver disease (NAFLD) occurs when fat is deposited into hepatocytes without a known cause (such as with alcoholic fatty liver disease). The deposition of fat may lead to hepatic inflammation (hepatitis) and may eventually lead to cirrhosis.
"Non-alcoholic fatty liver disease" (NAFLD) is differentiated by some into:
- non-alcoholic fatty liver (NAFL)
- signs of hepatic inflammation are absent
- non-alcoholic steatohepatitis (NASH)
- signs of hepatic inflammation are present
NAFLD has a prevalence of ~30% (range 10-46%) in the U.S. 2 and a prevalence worldwide of 6-35% 3. NASH has a prevalence of 3-5% 3.
It is more commonly seen at ages 40-60. No gender predominance has been noted.
Often asymptomatic, although vague abdominal pain has been reported. Hepatomegaly has been reported in a minority of patients. Elevated liver enzymes (such as AST/ALT) may be present, especially with NASH.
The pathogenesis fo NAFLD is not well understood, but it has been associated with dysmetabolic conditions:
The role of imaging is to demonstrate fat deposition in the liver, determine if cirrhotic changes are present, and to exclude other possible diagnoses. For general features of fatty deposition in the liver, see diffuse hepatic steatosis.
Liver biopsy may be needed in indeterminate situations to establish the diagnosis.
- findings are those of hepatic steatosis, with increased echogenicity and coarsened echotexture of the liver (see also: grading of diffuse hepatic steatosis)
- if steatohepatitis has progressed to cirrhosis, a nodular liver surface may be present in addition to other fibrotic changes
- diffuse hypoattenuation of the liver relative to the spleen
- non-contrast liver attenuation of <40 HU is specific, but not sensitive for diffuse hepatic steatosis
- IP/OP: drop in signal intensity in liver on the out-of-phase sequence, compatible with intracellular lipid deposition
Treatment and prognosis
No definitive treatment has been established for NAFLD, but weight loss is thought to eliminate one of the factors contributing to the condition.
Patients who develop cirrhosis from NASH are treated similarly to other patients with cirrhosis.
- alcoholic liver disease
- hepatitis C
- acute fatty liver of pregnancy
- medication-related hepatic steatosis
- Wilson disease
- 1. Caldwell SH, Crespo DM. The spectrum expanded: cryptogenic cirrhosis and the natural history of non-alcoholic fatty liver disease. J. Hepatol. 2004;40 (4): 578-84. doi:10.1016/j.jhep.2004.02.013 - Pubmed citation
- 2. Lazo M, Hernaez R, Eberhardt MS et-al. Prevalence of nonalcoholic fatty liver disease in the United States: the Third National Health and Nutrition Examination Survey, 1988-1994. Am. J. Epidemiol. 2013;178 (1): 38-45. doi:10.1093/aje/kws448 - Free text at pubmed - Pubmed citation
- 3. Williams CD, Stengel J, Asike MI et-al. Prevalence of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis among a largely middle-aged population utilizing ultrasound and liver biopsy: a prospective study. Gastroenterology. 2011;140 (1): 124-31. doi:10.1053/j.gastro.2010.09.038 - Pubmed citation
- 4. Hernaez R, Lazo M, Bonekamp S et-al. Diagnostic accuracy and reliability of ultrasonography for the detection of fatty liver: a meta-analysis. Hepatology. 2011;54 (3): 1082-90. doi:10.1002/hep.24452 - Free text at pubmed - Pubmed citation