Intrahepatic sequestered segment of liver presenting as focal fatty change.

Focal fatty change of the liver is a lesion that is often discovered on imaging studies and must be distinguished from space-occupying lesions. The pathogenesis is unknown. We report a lesion of focal fatty change in which the portal supply and biliary drainage were anomalous so that the lesion represents sequestered liver tissue. Because insulin favors the development of steatosis, the pathogenesis of focal fatty change could be explained if the aberrant portal supply contained more insulin than the main portal vein, as would occur if the portal supply arose from pancreatic veins via the parabiliary venous plexus of Couinaud. Furthermore, focal fatty sparing could be explained if the spared segment was supplied by veins draining from the stomach that carry blood with lower insulin levels than the main portal vein.