Non-alcoholic fatty liver disease

Last revised by Dr Daniel J Bell on 07 Jun 2022

Non-alcoholic fatty liver disease (NAFLD), also known as metabolic associated fatty liver disease, 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 even eventually to cirrhosis.

Non-alcoholic fatty liver disease (NAFLD) is divided by some into:

  • non-alcoholic fatty liver (NAFL)
    • signs of hepatic inflammation are absent
  • non-alcoholic steatohepatitis (NASH)
    • signs of hepatic inflammation are present

Non-alcoholic fatty liver disease has a prevalence of ~30% (range 10-46%) in the U.S. 2 and a prevalence worldwide of ~ 20% (range 6-35%) 3. Non-alcoholic steatohepatitis has a prevalence of 3-5% 3. It is common in children, with a prevalence of 10% 5. It is more commonly seen at ages 40-60 ref. No gender predominance has been noted ref.

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 non-alcoholic steatohepatitis. 

By definition, hepatic steatosis is present when 5% of the weight of the liver is intrahepatic fat 6

The pathogenesis of non-alcoholic fatty liver disease 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.

  • 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

No definitive treatment has been established for non-alcoholic fatty liver disease, but weight loss is thought to eliminate one of the factors contributing to the condition.

Patients who develop cirrhosis from non-alcoholic steatohepatitis are treated similarly to other patients with cirrhosis.

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