A biloma is an enclosed collection of bile that pools outside the bile ducts, typically within or around the liver. It forms when bile leaks from a damaged bile duct and becomes walled off by surrounding tissue, creating a distinct fluid-filled pocket. Unlike a free bile leak that spreads through the abdomen, a biloma has well-circumscribed margins, essentially forming its own capsule. Most bilomas develop as a complication of surgery, though they can also result from trauma or, rarely, appear on their own.
What Causes a Biloma
The most common cause is injury to the bile ducts during gallbladder removal surgery (cholecystectomy). Bilomas after cholecystectomy occur in roughly 0.3% to 2% of cases. Laparoscopic gallbladder surgery, while safer overall than open surgery, carries a small risk of nicking or clipping the bile ducts in a way that allows bile to seep out afterward. The leak may not become apparent until days or even weeks after the procedure.
Other causes include blunt or penetrating abdominal trauma, liver biopsies, tumor ablation procedures, and other surgeries involving the liver or bile ducts. In rare cases, a biloma forms spontaneously, sometimes triggered by a gallstone blocking a duct and causing enough pressure to rupture it. Regardless of the cause, the underlying mechanism is the same: bile escapes from a breach in the biliary system and collects in a space where it doesn’t belong.
Symptoms to Watch For
The hallmark symptom is pain or discomfort in the right upper part of the abdomen, just below the ribs on the right side. This is where the liver and gallbladder sit, and it’s where most bilomas form. Small bilomas may cause only mild, vague discomfort or no symptoms at all. Larger collections tend to produce more noticeable pain, along with nausea, loss of appetite, and sometimes fever.
If a biloma grows large enough to compress nearby bile ducts, it can cause jaundice (yellowing of the skin and eyes) because bile backs up into the bloodstream. Fever and chills are particularly important warning signs, as they suggest the biloma has become infected. An infected biloma can progress to a serious bloodstream infection if left untreated. On imaging, heavily compartmentalized bilomas are associated with a higher likelihood of infection.
How a Biloma Is Diagnosed
Ultrasound is typically the first imaging study, since patients often present with right-sided abdominal pain that initially looks like it could be many things. On ultrasound, a biloma appears as a dark, fluid-filled cyst. It can range from a small, well-defined pocket within the liver itself to a large, multi-chambered collection extending through the abdomen. The ultrasound may also reveal debris or blood clots floating inside the collection.
CT scans provide a more detailed picture and help determine the biloma’s size and exact location. Bilomas appear as low-density fluid collections on CT. However, CT alone can’t always distinguish a biloma from other post-surgical fluid collections like blood clots, abscesses, or benign cysts. MRI can add further detail: bilomas produce characteristic signal patterns that help narrow the diagnosis, and a rim of enhancement around the edges (from inflammation) is common. When infection is present, the internal walls of the biloma may also show enhancement.
A nuclear medicine scan called a HIDA scan is particularly useful when an active bile leak is suspected. This test uses a small amount of radioactive tracer that the liver processes just like bile. If bile is leaking, the tracer shows up outside the normal biliary pathway. In published case series, HIDA scans have detected 100% of confirmed bile leaks. A more advanced version that combines HIDA with CT imaging can pinpoint the exact location of the leak and the extent of the collection.
Treatment Options
Small, asymptomatic bilomas can sometimes be monitored with imaging alone, without any intervention. The body may gradually reabsorb a small collection over time. Most bilomas, however, require some form of treatment.
The first-line approach for a symptomatic biloma is percutaneous drainage, where a radiologist inserts a thin tube through the skin and into the collection under ultrasound or CT guidance. This allows the bile to drain out. In one reported case, 800 milliliters of bile-stained fluid was aspirated in a single session. If a residual collection remains after the initial drainage, a small pigtail catheter may be left in place to allow ongoing drainage over several days.
When bile continues to leak despite drainage, an endoscopic procedure called ERCP becomes necessary. During ERCP, a flexible scope is passed through the mouth and into the small intestine to access the bile duct opening. From there, a small cut can be made to widen the duct opening (reducing pressure in the biliary system), and a stent can be placed to redirect bile flow away from the leak site while it heals. If gallstones contributed to the problem, they can be removed during the same procedure.
Surgery is reserved for emergencies or cases where less invasive treatments fail. These percutaneous and endoscopic approaches are preferred over surgery as the initial treatment because they carry lower risk and shorter recovery times. Antibiotics are added whenever there are signs of infection.
Recovery and Outlook
When a biloma is identified and drained promptly, symptoms and abnormal liver tests typically resolve within a few weeks to a few months. In documented cases, complete resolution of symptoms and lab values has occurred within three months of drainage. The prognosis is generally good as long as the underlying bile leak is addressed and infection is prevented or treated early.
The key factor in recovery is whether the source of the bile leak seals on its own or needs additional intervention. A biloma caused by a small duct injury during surgery often resolves with drainage alone, as the injured tissue heals. Larger duct injuries or persistent leaks may require stenting or, in some cases, surgical repair, which extends the recovery timeline. After treatment, follow-up imaging is used to confirm the collection has resolved and no new fluid is accumulating.