Diagnostic Ultrasound - Abdomen and Pelvis

Biliary Ductal Gas
Diagnoses: Biliary System
TERMINOLOGY
• Definition: Gas within biliary tree including bile ducts or
gallbladder
• Synonyms: Pneumobilia, aerobilia
IMAGING
• Bright echogenic foci in linear/branching configuration
following portal triads associated with "dirty"
shadowing/reverberation artifact
• Most commonly seen within intrahepatic bile ducts, though
may also involve extrahepatic bile ducts and gallbladder
• Movement of gas, best demonstrated following change in
patient's position
TOP DIFFERENTIAL DIAGNOSES
• Portal venous gas
○ Branching echogenic foci in periphery of liver
parenchyma within portal venous radicle
• Intrahepatic ductal stones/sludge
KEY FACTS
○ Echogenic foci casting dense posterior acoustic
shadowing ± dilated duct
• Hepatic arterial calcifications
○ Hyperechoic lines accompanying portal veins
PATHOLOGY
• Etiology
○ Previous biliary intervention, classically papillotomy
○ Cholecysto-enteric/choledocho-enteric fistula
○ Biliary infection with gas-forming organism
○ Recurrent pyogenic cholangitis
CLINICAL ISSUES
• Majority will resolve spontaneously
• Prognosis depends on underlying etiology
DIAGNOSTIC CHECKLIST
• Examine patient in supine and oblique positions to
demonstrate movement of gas
• Consider CT for improved delineation
(Left) Transverse US through
the left hepatic lobe
demonstrates multiple linear
echogenic areas along the
expected course of the biliary
tree ſt, some with associated
with posterior shadowing ,
compatible with intrahepatic
biliary gas. (Right) Transverse
US through the left hepatic
lobe demonstrates linear
echogenic foci ſt associated
with "dirty" posterior
shadowing , compatible
with intrahepatic biliary
ductal gas.
(Left) Transverse US through
the right hepatic lobe
demonstrates several
echogenic foci ſt in linear
configurations, with "dirty"
posterior shadowing,
compatible with biliary ductal
gas. (Right) Transverse US
through the right hepatic lobe
demonstrates several
echogenic foci ſt in linear
configurations which are
associated with "dirty"
posterior shadowing ,
compatible with biliary ductal
gas.
332