KEY FACTS
Terminology
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Definition: Gas within biliary tree, including bile ducts or gallbladder
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Synonyms: Pneumobilia, aerobilia
Imaging
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Bright, echogenic foci in linear/branching configuration following portal triads associated with “dirty” shadowing/ring down artifact
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Most commonly seen within intrahepatic bile ducts, though may also involve extrahepatic bile ducts and gallbladder
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Movement of gas, best demonstrated following change in patient’s position
Top Differential Diagnoses
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Portal venous gas
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Branching echogenic foci in periphery of liver parenchyma within portal venous radicle
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Intrahepatic ductal stones/sludge
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Echogenic foci casting dense posterior acoustic shadowing ± dilated duct
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Hepatic arterial calcifications
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Hyperechoic parallel lines accompanying portal veins
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More common in chronic dialysis patients
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Calcified hepatic granuloma
Pathology
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Etiology
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Previous biliary intervention, classically papillotomy
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Cholecystoenteric/choledochoenteric fistula
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Biliary infection with gas-forming organism
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Recurrent pyogenic cholangitis
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Clinical Issues
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Majority will resolve spontaneously
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Prognosis depends on underlying etiology
Scanning Tips
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Examine patient in supine and oblique positions to demonstrate movement of gas
