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Diagnosis

Emphysematous cholecystitis (Answer choice 3).

Radiology Findings

• Ultrasound
  Gallstones are present. There is increased echogenicity within the non-dependent portion of the gallbladder, with 'dirty' posterior shadowing, concerning for air in the gallbladder lumen. There are echogenic areas with ringdown artifact in the liver that represent pneumobilia or portal venous gas. Gallbladder wall thickening is present. No pericholecystic fluid is seen. The common bile duct is dilated but within normal limits for the patient's age.
• CT
  Pneumobilia is present and mild biliary ductal dilation is seen. There is pneumatosis within the wall of the gallbladder and gallbladder wall thickening and hemorrhagic products within the lumen of the gallbladder. There is a small amount pericholecystic fluid and a small amount of fluid within Morrison's pouch as well. The common hepatic duct adjacent to the gallbladder measures is mildly dilated but decompresses distal to the gallbladder.

Differential Diagnosis

• Emphysematous cholecystitis.
• Paraduodenal abscess.
• Periappendiceal abscess in a malpositioned appendix.
• Ascending cholangitis.
• Biliary-enteric fistula.
• Gallbladder lipomatosis (Plain-film mimic of gallbladder wall gas).