Pneumobilia is the presence of gas in the biliary system.

It is typically detected by ultrasound or a radiographic imaging exam, such as CT, or MRI.

While the presence of air within biliary system is not harmful, this finding may alternatively suggest a pathological process, such as a biliary-enteric anastomosis, an infection of the biliary system, an incompetent sphincter of Oddi, or spontaneous biliary-enteric fistula.

In a healthy individual with normal anatomy, there is no air within the biliary tree.

When this finding is present, it may be secondary to: Other rare causes that have been reported include duodenal diverticulum, paraduodenal abscess, operative trauma, and carcinoma of the duodenum, stomach and bile duct.