Introduction
- Focal fatty infiltration may mimic neoplastic or other
low-density parenchymal lesions, including abscesses and
hemangiomas. Thus, it is imperative that the radiologist
interpreting the images is well aware of the appearance of focal
fatty liver lesions in various radiological modalities.
- Focal fat is often found near the falciform ligament or in the
gallbladder fossa. Outside of the gallbladder fossa or the
vicinity of the falciform ligament, focal fat often has a
geographic distribution.
- A key feature of focal fat is that vessels are seen
crossing through it in a normal, non-displaced fashion.
Pathology and Pathogenesis
- Etiology is mainly due to alcoholic and non-alcoholic causes:
- Alcohol causes accumulation of fatty acids as triglycerides
in the liver because of enhanced hepatic lipogenesis, decreased
hepatic release of lipoproteins, increased mobilization of
peripheral fat, enhanced hepatic uptake of circulating lipids,
and decreased fatty acid oxidation.
- Fat accumulation in non-alcoholic steatohepatitis (NASH)
appears to be etiology specific. For example, in obesity,
hypersecretion of triglyceride-rich lipoproteins may be related
to increased fatty acid synthesis.
- Anatomically, focal fatty change consists of pale,
yellow-white nodules that are primarily subcapsular. They have a
scalloped border and, occasionally, central veins at the
periphery. Branches of the portal and hepatic veins typically
transverse it without change in their course. They usually cause
no mass effect.
- Histologically, they are circumscribed nodules of severe fatty
change surrounded by liver tissue with little or no fatty change.
The majority of hepatocytes have a single fat globule displacing
the nucleus. Other associated findings include cirrhosis,
necrosis, and centrilobular congestion.
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