Focal solitary hypoechoic area in hepatic fatty infiltration: a cause of hepatic pseudomass in ultrasound examination.

A unusual pattern of hepatic fatty infiltration was detected sonographically in 43 patients over a 2-year period. At appropriate gain settings and time gain compensations, the liver parenchyma demonstrated diffuse increased echogenicity except for a solitary hypoechoic area with relatively distinct margins, usually locate in the medial segment of the left hepatic lobe or right lobe in pericholecystic, perivascular or subcapsular locations. This hypoechoic focus varied in size between 15 and 50 mm and was typically ovoid, but was occasionally spherical or irregular in shape. Fourteen patients with such skip area underwent percutaneous needle biopsy because of concern that there was a space-occupying mass. Microscopic examination of specimens from the hypoechoic region revealed normal hepatic parenchymal cells, while tissue samples from the surrounding liver had high fat levels. In the remaining 29 patients, correlative radiologic studies supported the diagnosis of fatty liver and excluded a central-mass lesion. A localized area of normal hepatic tissue should be considered among the possible hypoechoic periportal area demonstrated within a fatty liver.