Clinical

Gas in the biliary tree is most commonly secondary to surgical procedures such as choledochoenterostomy or sphincterotmy of the sphincter of Oddi. It may also arise in the setting of trauma, infection by gas producing organisms (i.e. emphysematous cholecystitis), fistulas connecting the biliary system and the intestinal tract (i.e. from dudodenal ulcers, or gallstones), malignant involvement of the ampulla of Vater, or as a congenital anomaly.

Radiological findings

Ultrasound is the modality of choice for visualizing gas in the biliary tree. Air in the bile ducts generally causes bright linear or globular reflections with shadowing and ring-down artifacts. The gas will move with patient positioning. On plain film, biliary gas may be seen outlining the bile ducts but it is important to be cautious in making this diagnosis as normal periductal fat that surrounds and parallels the course of the bile ducts may give the appearance known as pseudopneumobilia.