Biloma

Bilomas refer to extrabiliary collections of bile. They can be either intra- or extrahepatic. 

Terminology

"Biloma" is used variably in the reported literature. Many authors use the term to exclusively refer to intrahepatic bile collections or other bilious collections which are discretely organized. Some authors include free biliary leak into the peritoneum (choleperitoneum: a rarely used term).

Epidemiology

Biloma is a rare medical condition that occurs in 0.3% to 2.0% of cases ⁸.

Clinical presentation

Although usually asymptomatic, they may present with symptomatic bile peritonitis ⁷.

Pathology

They have many potential causes:

• spontaneous 

• trauma

• post instrumentation

  • transcatheter arterial chemoembolisation (TACE)

  • percutaneous ethanol injection

  • microwave ablation

  • percutaneous biliary drainage

  • post surgical, e.g. injury to subvesical bile ducts following cholecystectomy ⁶

70% of bilomas are localized to the right upper quadrant, whereas the remaining 30% develop in the left upper quadrant. A biloma may wall off or may continue to demonstrate active bile leakage.

Radiographic features

The goals of imaging in the assessment of biloma are:

• confirm the presence of a bile leak

• determine if it is extrahepatic or intrahepatic

• describe its extent

• assess for associated biliary obstruction

CT

Bilious fluid is water attenuation, usually seen collecting in the right upper quadrant. CT intravenous cholangiography can demonstrate a communication between the biliary tree and the biloma, localizing the leak. 

MRI

Bilious fluid demonstrates variable signal intensity on T1-weighted imaging, and high signal intensity on T2-weighted imaging, similar to the signal intensity of gallbladder fluid.

Both gadolinium and manganese-based MRI contrast agents that are excreted through the biliary system are available. A delayed enhanced MRI examination using one of these agents may be useful to confirm that a localized fluid collection is composed of bile and to identify the site of bile leak ⁷.

Nuclear medicine

Tc⁹⁹ diisopropyl iminodiacetic acid (DISIDA) scans are useful for confirmation of an active bile leak.

Treatment and prognosis

Treatment options include:

• pigtail drainage (under US/CT guidance)

• surgical drainage

Management of bilomas can also involve treating any associated biliary tract obstruction which can both complicate and cause bilomas. Surgical repair of the source of underlying biliary tract bile leak may also be required.

Differential diagnosis

General imaging differential considerations include:

• biliary cystadenoma

• hepatic abscess