Gallbladder empyema

Gallbladder empyema (suppurative cholecystitis ¹) is an uncommon complication of cholecystitis and refers to a situation where the gallbladder lumen is filled and distended by purulent material (pus).

Epidemiology

There is an increased incidence in those with diabetes mellitus ² and/or advanced atherosclerotic disease ⁷.

Clinical presentation

While patients with a gallbladder empyema may experience symptoms similar to those with acute uncomplicated cholecystitis (fever, chills, rigors, and right upper quadrant abdominal pain), signs of sepsis may not always be present.

Pathology

The gallbladder neck is usually obstructed by a calculus (or rarely from a malignant mass such as an underlying cholangiocarcinoma) which prevents pus from draining through the cystic duct ⁵. 

Radiographic features

Ultrasound

Ultrasound may show the usual sonographic features of cholecystitis with added echogenic content within the gallbladder lumen (this feature is however not specific for an empyema). In cases of extensive calculous cholecystitis where gallstones fill the galbladder lumen it may be difficult to assess the echogenicity of bile and further cross-sectional imaging may be required.

CT

CT may show general imaging features of cholecystitis with added high-attenuating material (representing pus) within the distended gallbladder lumen. Again this feature is nonspecific and is often difficult to differentiate from sludge within the gallbladder. 

MRI

MRI sometimes may be helpful in distinguishing pus from sludge by using heavily T2 weighted sequences, which may show fluid-fluid levels with dependent layering of purulent bile. On other MR sequences images, pus or purulent bile may be difficult to demonstrate ². The purulent component is usually of lower signal on T2 weighted images ^7,8.

Treatment and prognosis

Management options for suppurative cholecystitis include both emergent cholecystectomy and percutaneous catheter drainage, also termed percutaneous cholecystostomy (which can later be followed by a cholecystectomy) ^1,5,6. The latter option is usually reserved for those with additional co-morbidities ⁶. The rate of conversion of a laparoscopic cholecystectomy to an open procedure is considered greater than that with cases of uncomplicated acute cholecystitis. Gallbladder empyema is associated with significant morbidity and mortality ⁹.

Differential diagnosis

On imaging possible considerations include

• gangrenous cholecystitis
  • asymmetric GB wall thickening with ulceration and irregularity of wall
  • ± no Doppler flow
  • diminished C+ enhancement of portions of GB wall
  • ± pericholecystic collection/abscess
• emphysematous cholecystitis
  • luminal gas with "dirty" posterior acoustic shadowing
  • ring-down artifact from gas bubbles
  • champagne sign
• gallbladder distension from cholecystitis without pus
• gallbladder distension with sludge within
• hepatic abscess adjacent to or intimately close to the gallbladder