A middle aged man presented with right upper quadrant pain and fever. Ix showed abnormal liver function tests.
There are multiple small, bright, shadowing foci seen within the liver, they are predominantly seen centrally. An echogenic shadowing mass seen in the longitudinal view was fat surrounding the falciform ligament (labelled with + + in image 2, the longitudinal view in image 3 confirms this NB this is normal). The CBD is dilated. There is a 1cm echogenic mass seen in the distal CBD.
Pneumobilia tends to be centrally distributed, in contrast to portal vein gas which tends to be peripherally distributed. It is most commonly due to sphincter of Oddi incompetence (e.g. post ERCP) or fistula (e.g. post surgical anastamosis such as Whipple's procedure), but may be due to infection with gas forming organisms (ascending cholangitis). This patient had previously undergone ERCP, but was febrile, so either cause was possible. They were treated with antibiotics and underwent ERCP to remove the CBD stone.
Abnormalities should always be viewed in 2 planes to determine their cause. For example, fat around the ligamentum teres can easily appear as a hyperechoic lesion, but the true cause is easily seen when the probe is rotated to be parallel with the ligament.