Metabolic dysfunction associated steatotic liver disease

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

Terminology

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

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

Epidemiology

NAFLDNon-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. NASHNon-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.

Clinical presentation

Often asymptomatic, although vague abdominal pain has been reported. HepatomegalyHepatomegaly has been reported in a minority of patients. Elevated liver enzymes (such as AST/ALT) may be present, especially with NASHnon-alcoholic steatohepatitis. 

Pathology

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

The pathogenesis of NAFLDnon-alcoholic fatty liver disease is not well understood, but it has been associated with dysmetabolic conditions:

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

Radiographic features

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.

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

CT

• 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

MRI

• 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 NAFLDnon-alcoholic fatty liver disease, but weight loss is thought to eliminate one of the factors contributing to the condition.

Patients who develop cirrhosis from NASHnon-alcoholic steatohepatitis 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 steatosis
  • focal hepatic steatosis