Gas in the biliary tree on plain abdominal X-ray is suggestive of:
Clinically "silent" biliary-enteric fistulas occurring as a complication of acute cholecystitis and it can be diagnosed by finding gas in the biliary tree on plain abdominal films. Barium contrast studies or endoscopy of the upper gastrointestinal tract or colon may demonstrate the fistula. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 2622
Empyema of the gallbladder
Mirizzi syndrome
Biliary enteric fistula
Porcelain gallbladder