Pneumobilia is the presence of gas in the biliary system.

Pneumobilia in the non operated patient, is almost pathognomonic of some form of internal biliary fistula.

It is essential to distinguish between air in the biliary tree from air in the portal venous system in making a diagnosis of pneumobilia.

Another radiological finding that can be seen in such biliary enteric fistulas is pneumobilia which is the presence of air in the biliary tree.

Classic findings of pneumobilia (air within the biliary tree), small bowel obstruction, and radiolucent gallstone on abdominal plain films is known as Rigler's triad.