• GB empyema: Pus-filled, inflamed, and distended GB secondary to acute cholecystitis with suppurative intraluminal infection
IMAGING
• Hydrops
CECT: Distended GB filled with low-density contents
– Usually no wall thickening, pericholecystic fluid, or adjacent fat stranding
US: Distended GB with anechoic and simple contents
– GB wall appears thin or normal
– Negative sonographic Murphy sign
– Gallstones usually (but not always) present
• Empyema
CECT: Distended GB with intraluminal contents > 15 HU
– Wall thickening with pericholecystic fat stranding and fluid (similar to conventional cholecystitis)
– Advanced cases may show gangrene or perforation
US: Markedly distended GB with echogenic pus in lumen
– GB wall appears thickened
– Sonographic Murphy sign often positive
– Gallstones usually (but not always) present
PATHOLOGY
• GB hydrops caused by chronic GB outlet obstruction (most commonly due to impacted stone)
• Empyema caused by bacterial infection of bile within inflamed GB, usually in setting of acute cholecystitis
CLINICAL ISSUES
• Hydrops: RUQ pain without fever or signs of infection
• Fever or ↑ WBC with dilated GB concerning for empyema
• Cholecystectomy for GB hydrops if patient is symptomatic
• Urgent cholecystectomy for empyema
(Left) Oblique ultrasound shows an enlarged gallbladder in a 5 year old with fever and right upper quadrant pain. The hydropic gallbladder led to the diagnosis of Kawasaki disease, a known predisposing factor for hydrops in children. (Courtesy R.J. Fleck, Jr., MD.)
(Right) Axial CECT in a cirrhotic patient with RUQ pain demonstrates that the gallbladder is distended but thin-walled, and a stone is present within the cystic duct , findings consistent with gallbladder hydrops.
(Left) Ultrasound in an elderly patient with sepsis shows a massively dilated and elongated gallbladder with a thick wall and rounded but mobile internal echogenic sludge.
(Right) Coronal NECT in the same patient shows the dilated gallbladder with thickened wall . Because the patient was considered a poor surgical candidate, she was treated with percutaneous cholecystostomy, which yielded thick bile with a heavy growth of bacteria, consistent with empyema of the gallbladder.
TERMINOLOGY
Synonyms
• Hydrops: Mucocele
• Empyema: Suppurative cholecystitis
Definitions
• Hydrops: Distended gallbladder (GB) secondary to chronic obstruction filled with watery mucoid material
Content is usually sterile without GB inflammation
• Empyema: Pus-filled, inflamed, and distended GB secondary to acute cholecystitis with suppurative intraluminal infection
IMAGING
General Features
• Best diagnostic clue
Rounded, distended GB filled with either anechoic watery mucoid content (hydrops) or echogenic pus (empyema)
• Location
Markedly distended GB can extend downwards into pelvis in most severe cases
• Size
GB distended > 5 cm transverse diameter
Size can reach up to 1.5 liters
• Morphology
Rounded distended GB
Imaging Recommendations
• Best imaging tool
Ultrasound
• Protocol advice
Grayscale and color Doppler ultrasound
CT Findings
• Hydrops
Markedly distended GB filled with low-density contents
Usually thin wall with minimal inflammatory change
– Typically no evidence of overt wall thickening, pericholecystic fluid, or adjacent fat stranding
• Empyema
Markedly distended GB with high-density intraluminal contents > 15 HU
GB wall thickened > 5 mm
Gallstones usually present, but not always visible on CT
Pericholecystic fluid and fat stranding
Advanced cases may demonstrate evidence of wall gangrene or perforation, including areas of diminished wall enhancement, frank defect in GB wall, or pericholecystic fluid collection
MR Findings
• Hydrops
Distended GB with internal contents demonstrating simple fluid signal (high T2WI and low T1WI)
No evidence of wall edema or adjacent inflammation
Gallstones usually present (usually visible as signal voids on all sequences)
• Empyema
Distended GB with internal contents demonstrating variable signal depending on proportion of bile, pus, and blood
High signal edema in thickened GB wall on T2WI
Pericholecystic fluid and fat stranding
Ultrasonographic Findings
• Markedly distended GB in both hydrops and empyema
GB wall appears thin or normal in hydrops
GB wall appears thickened (often asymmetric) in empyema
• Sonographic Murphy sign negative in hydrops, but often positive in empyema
• GB contents appear anechoic and simple in hydrops
• Echogenic pus in lumen, similar in echogenicity to sludge, in empyema
• Gallstones often present in both hydrops and empyema, but may also be acalculous
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, findings consistent with gallbladder hydrops.
and rounded but mobile internal echogenic sludge.
. Because the patient was considered a poor surgical candidate, she was treated with percutaneous cholecystostomy, which yielded thick bile with a heavy growth of bacteria, consistent with empyema of the gallbladder.
