Metabolic dysfunction associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), is a subtype of steatotic liver disease. It occurs when patients have hepatic steatosis and at least one of five cardiometabolic risk factors. The deposition of fat may lead to hepatic inflammation (hepatitis) and even eventually to cirrhosis.
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Terminology
In June 2023, the term NAFLD was changed to MASLD to incorporate new thinking and categorization of steatotic liver diseases 7.
The entity non-alcoholic fatty liver disease (NAFLD) had previously been divided by some into:
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non-alcoholic fatty liver (NAFL)
signs of hepatic inflammation are absent
with the new nomenclature, this would be metabolic dysfunction associated steatotic liver (MASL)
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non-alcoholic steatohepatitis (NASH)
signs of hepatic inflammation are present
with the new nomenclature this would be metabolic dysfunction associated steatohepatitis (MASH)
Epidemiology
MASLD has a prevalence of ~30% (range 10-46%) in the U.S. 2 and a prevalence worldwide of ~ 20% (range 6-35%) 3. Metabolic-associated 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. Hepatomegaly has been reported in a minority of patients. Elevated liver enzymes (such as AST/ALT) may be present, especially with metabolic-associated steatohepatitis.
Pathology
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:
obesity (particularly central obesity)
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
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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 MASLD, 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.
Differential diagnosis
other steatotic liver diseases, including alcohol-associated liver disease
medication-related hepatic steatosis
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