Cholecystostomy (as bridge to cholecystectomy) in high-risk, poor surgical candidates
(Left) Ultrasound image in an elderly diabetic man with fever demonstrates echogenic reflectors in the gallbladder (GB) wall with “dirty” acoustic shadowing and “ring down” artifact , classic for emphysematous cholecystitis.
(Right) Axial CECT in a patient with melanoma shows widespread liver metastases . Gas is present within the GB lumen , and the GB wall appears to be perforated . Gangrenous perforation of the GB was seen at surgery, possibly related to the patient’s chemotherapy.
(Left) Color Doppler ultrasound in a diabetic patient shows a distended GB containing heterogeneous material, including some foci of very high-intensity echoes within the lumen and wall of the GB, and virtually no flow within the GB wall.
(Right) Axial CECT in the same patient shows the distended GB with gas bubbles within the wall and lumen corresponding to the echogenic foci identified on sonography, in keeping with emphysematous cholecystitis.
TERMINOLOGY
Synonyms
• Clostridial cholecystitis
Definitions
• Rare form of acute cholecystitis due to secondary infection by a gas-forming organism
IMAGING
General Features
• Best diagnostic clue
Curvilinear intramural gas or intraluminal gas resulting in a gas-fluid level within the gallbladder (GB)
• Location
Lumen or wall of GB
• Size
Ranges from several bubbles to extensive intramural or intraluminal gas
• Morphology
Curvilinear intramural gas or intraluminal gas resulting in a gas-fluid level
Imaging Recommendations
• Best imaging tool
NECT or CECT
Plain radiographs should not be utilized if there is high suspicion for this diagnosis
Radiographic Findings
• Radiography
Intraluminal (rounded) or intramural (curvilinear) gas in expected position of GB
– Air-fluid level may be present in upright or decubitus films
Insensitive for detection of emphysematous cholecystitis: Only identified 45% of cases in 1 series
– Cases where findings are apparent on radiography tend to be more severe
CT Findings
• Best modality for identifying intramural or intraluminal GB gas (100% sensitive)
Gas within pericholecystic abscess or free intraperitoneal air may be present with perforation
Rarely portal venous gas due to GB wall ischemia
Extension of gas into remainder of biliary system suggests severe form of infection
• Gallstones seen in only ∼ 50% of patients: Acalculous cholecystitis carries higher risk
• Other findings are similar to uncomplicated cholecystitis
GB wall thickening (> 3 mm)
GB distension > 5 cm (in short axis)
Pericholecystic free fluid and fat stranding
Irregularity, ulcerations, and absent enhancement of GB wall due to gangrene
MR Findings
• Intraluminal and intramural gas appear as signal voids on all pulse sequences
Floating signal void due to gas bubbles in nondependent portion of GB (unlike stones which are dependent)
Low signal intensity rim around margin of GB due to intramural gas
Gas causes field inhomogeneity and susceptibility artifact at air-tissue interface
• Irregular wall thickening with areas of heterogeneous T1 and T2 hyperintensity indicative of intramural hemorrhagic necrosis
• Other findings similar to uncomplicated cholecystitis
Low signal (T1WI and T2WI) intensity stones in dependent portion of GB (particularly in neck and cystic duct)
• Gas in GB wall manifests as highly echogenic reflectors with dense posterior acoustic “dirty” shadowing
Shadowing is not anechoic (as is seen with gallstones), but is of intermediate echogenicity
Echogenic reflectors associated with “ring-down” or “comet tail” artifact
• Intraluminal gas bubbles should be mobile on real-time US and may rise up to nondependent portions of GB similar to bubbles of champagne (champagne sign)
Gas may change position when patient is moved
• Cholelithiasis (in 50% of patients), GB wall thickening, pericholecystic free fluid, and pericholecystic echogenic fat (due to inflammation)
• US has high specificity, but lower sensitivity, for detection of emphysematous cholecystitis
Echogenic gas in GB lumen may be misinterpreted as gas-filled bowel, stone-filled GB, or porcelain GB
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in the gallbladder (GB) wall with “dirty” acoustic shadowing and “ring down” artifact 
, classic for emphysematous cholecystitis.
. Gas is present within the GB lumen 
, and the GB wall appears to be perforated 
. Gangrenous perforation of the GB was seen at surgery, possibly related to the patient’s chemotherapy.
within the wall and lumen corresponding to the echogenic foci identified on sonography, in keeping with emphysematous cholecystitis.
