Non-alcoholic fatty liver disease
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.
Terminology
"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
Epidemiology
NAFLD has a prevalence of ~30% (range 10-46%) in the U.S. and a prevalence worldwide of 6-35% . NASH has a prevalence of 3-5% .
It is more commonly seen at ages 40-60. No gender predominance has been noted.
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 NASH.
Pathology
The pathogenesis fo NAFLD is not well understood, but it has been associated with dysmetabolic conditions:
- diabetes mellitus
- obesity (particularly central obesity)
- dyslipidemia
- 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 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
