Overview
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.