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Air in the Biliary System

General Considerations

  • Air in the biliary tree, also known as pneumobilia
  • Most frequently from the following causes
    • Incompetent Sphincter of Oddi
    • Recent instrumentation, as in ERCP, or surgery, as in spincterotomy
    • Fistulous connection with the GI tract, as in gallstone ileus
  • It is rarely due to gas-forming infection, as in cholangitis or emphysematous cholecystitis

Clinical Findings

  • Usually benign or asymptomatic when caused by incompetent sphincter or surgery

Imaging Findings

  • Several, air containing-tubular structures seen in the region of the hilus of the liver
  • The common bile duct is frequently recognizable
  • There may be other, left and right biliary radicals, filled with air
  • Since air produces echogenic artifacts on ultrasound, pneumobilia is visible on US

Differential Diagnosis

  • Portal venous gas
    • Usually a more ominous finding than pneumobilia
    • Can be differentiated by the peripheral nature of innumerable air-containing branching structures near the outer edge of the liver rather than centrally


Air in the Biliary System

Air in the Biliary System. Close-up of the right upper quadrant shows a tubular structure containing air (red arrow) representing the common bile duct and several air-containing biliary radicals (white arrows).

The air-filled left hepatic duct: the saber sign as an aid to the radiographic diagnosis of pneumobilia.BJ Lewandowski, C Withers, and F Winsberg. Radiology. 1984;153 (2): 329-32.