Pneumobilia: Clinical Significance and Diagnostic Implications
Pneumobilia indicates an abnormal communication between the biliary tract and the gastrointestinal system, or less commonly, infection by gas-forming bacteria, and requires immediate investigation to determine if surgical intervention is needed. 1, 2
Primary Causes of Pneumobilia
The most common etiologies include:
- Biliary-enteric fistula (most frequent cause): Spontaneous fistula formation, typically from gallstone disease causing cholecystoduodenal or choledochoduodenal fistula 3, 2
- Iatrogenic biliary-enteric anastomosis: Post-surgical connections including Whipple procedure, choledochojejunostomy, or surgical sphincteroplasty 3, 2
- Endoscopic sphincterotomy: Following ERCP with papillosphincterotomy causing incompetence of the sphincter of Oddi 3, 2
- Gas-forming infections: Emphysematous cholecystitis or pyogenic cholangitis with gas-producing organisms 1, 4, 2
- Blunt abdominal trauma: Rare but documented cause of traumatic biliary-enteric communication 4
Critical Distinction on Imaging
On ultrasound, pneumobilia produces increased echogenicity with comet-tail artifact caused by gas in the biliary tree, which can be subtle and easily overlooked. 1
- CT scanning is superior for identifying pneumobilia and distinguishing it from portal venous gas, which has different management implications 2, 5
- Air in the common bile duct is seen in 100% of CBD-enteric fistulas versus only 57% of gallbladder-enteric fistulas 5
- A contracted gallbladder is present in 86% of gallbladder-enteric fistulas but only 33% of CBD-enteric fistulas 5
Clinical Significance and Management Approach
Despite historical teaching that asymptomatic pneumobilia is benign, recent evidence demonstrates it can lead to serious complications including cholangitis and bacteremia, even after prolonged asymptomatic periods. 6
- Pneumobilia from spontaneous biliary-enteric fistula is considered serious pathology usually requiring surgical intervention 3
- Patients with gallstone-related fistulas should undergo cholecystectomy with fistula closure to prevent complications 3
- Laparoscopic cholecysto-fistulectomy by skilled surgeons is the first-choice treatment to reduce morbidity and costs 3
- Conservative management may be appropriate only for traumatic pneumobilia in stable patients 4
Key Diagnostic Pitfalls
- Pneumobilia may be confused with adjacent bowel gas on ultrasound; optimization of gain settings and scanning from multiple directions is essential 1
- The finding is subtle and can produce comet-tailing similar to cholesterol stones, requiring careful evaluation 1
- Do not assume pneumobilia is benign simply because the patient is asymptomatic—investigate the underlying cause as serious complications can develop 6