Fat pad vs. anterior subphrenic abscess: a new real-time sign

An echo-poor band of fat is seen between the anterior surface of the left lobe of the liver and the anterior abdominal wall in 25% of patients undergoing an abdominal scan. A similar appearance can be seen in an anterior subphrenic abscess. Normally, with respiration the liver can be seen to slide deeply to this fat band. If the band is due to subphrenic abscess, there is a differential movement due to fixation of the anterior part of the liver. This feature was seen in 4 patients proven to have subphrenic abscesses. This real-time sign is helpful in differentiating if the band is due to fat or to subphrenic abscess.