Metabolic dysfunction associated steatotic liver disease

Nonalcoholic 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.

Terminology

"Nonalcoholic fatty liver disease" (NAFLD) is differentiated by some into:

• nonalcoholic fatty liver (NAFL)
  • signs of hepatic inflammation are absent
• nonalcoholic steatohepatitis (NASH)
  • signs of hepatic inflammation are present

Epidemiology

NAFLD has a prevalence of 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.

Clinical Presentationpresentation

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) maybemay be present, especially with NASH. 

Pathology

NAFLD has been associated with dysmetabolic conditions:

• diabetes mellitus
• obesity (particularly central obesity)
• dyslipidemiadyslipidaemia
• hypothyroidism

The pathogenesis of NAFLD is not well-understood understood.

Radiographic features

The role of imaging is to demonstrate fat deposition in the liver, determine if cirrhotic changes are present, and excluding otherto exclude other possible diagnoses. For general features of fatty deposition in the liver, see: diffuse hepatic steatosis.

Ultrasound

• 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, the a nodular liver surface may be present in addition to other fibrotic changes

CT

• diffuse hypoattenuation of the liver relative to the spleen
  • noncontrast liver attenuation of <40 is specific, but not sensitive for diffuse hepatic steatosis

MRI

• IP/OP: drop in signal intensity in liver on the out-of-phase sequence, compatible with intracellular lipid deposition

Liver biopsy may be needed in indeterminate situations to establish the diagnosis.

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.

Differential diagnosis

• alcoholic liver disease
• hepatitis C
• acute fatty liver of pregnancy
• medication-related hepatic steatosis
• Wilson disease

See also

• hepatic fatty infiltration
  • diffuse hepatic fatty infiltration
  • focal hepatic fatty infiltration