What Is It, Causes, and More

Author:Nikol Natalia Armata

Editors:Alyssa Haag,Józia McGowan, DO,Kelsey LaFayette, DNP, RN

Illustrator:Abbey Richard

Copyeditor:David G. Walker

What is pneumobilia?

Pneumobilia, also known as aerobilia, refers to the presence of air within the biliary system (i.e., bile ducts, gallbladder, and liver) and typically indicates a possible communication between the biliary system and the gastrointestinal (GI) tract. It is usually identified by the presence of air bubbles, ranging from 2 to 5 millimeters, in the biliary tree, most commonly found towards the liver hilum (i.e., the region where the portal vein and hepatic artery enter the liver and the hepatic duct exits).

Anatomical illustration of the liver, biliary tree, and intestinal tracts.

What causes pneumobilia?

The underlying causes of pneumobilia are typically the result of an abnormal communication between the biliary tract and the intestines or infection by gas-forming bacteria. The most common conditions associated with pneumobilia are biliary-enteric surgical anastomosis, incompetence of the sphincter of Oddi, spontaneous biliary-enteric fistula, recent biliary instrumentation, infections, and biliary-bronchopleural fistulas.

Biliary-enteric surgical anastomosis (i.e., the surgical connection between the biliary tree and GI tract) is a very common surgical procedure conducted during surgeries, like cholecystoenterostomy (i.e., a surgery in which the gallbladder is joined to the small intestine to relieve an extrahepatic biliary tract obstruction), and Whipple procedure, which is a procedure that removes the head of the pancreas, the first part of the small intestine, the gallbladder, and the bile duct. The Whipple procedure is usually used to treat pancreatic cancers and other pathologies at the head of the pancreas, the duodenum, or bile duct. While trying to create a permanent connection between the biliary and the GI system, air may accumulate in the biliary tree. 

Less invasive procedures that concern the biliary system can also result in pneumobilia. During an Endoscopic Retrograde CholangioPancreatography (ERCP) and a common bile duct stent placement, small amounts of air can get trapped within the biliary tree. During ERCPs, the endoscope enters through the esophagus, goes to the stomach, and into the duodenum where it releases air to secure a better view. Then, the ampulla of Vater (i.e., the opening where the bile and pancreatic ducts empty into the duodenum) is located, and a thin, flexible tube called a catheter slides through the sphincter of Oddi (which surrounds the ampulla of Vater) and into the bile ducts. A contrast medium is subsequently injected into the ducts through the catheter to make them more visible. This communication between the GI tract and the biliary system may lead to pneumobilia.

The incompetence of the sphincter of Oddi can also allow air to flow from the GI tract to the biliary tree. Usually, this is the result of sphincterotomy or the passage of a gallstone that injures the biliary tree, but it may also result from scarring, like in chronic pancreatitis; medications, like atropine; and less frequently, congenital incompetence of the sphincter. Similarly, pneumobilia can result from a spontaneous biliary-enteric fistula, resulting from a complication of chronic cholelithiasis, peptic ulcer disease, trauma, or neoplasms (e.g., cholangiocarcinoma). 

Infections are a leading cause of pneumobilia in many individuals. In cholangitis, air can be produced in the biliary tree by gas-forming microorganisms (e.g., Clostridium perfringens, Klebsiella pneumoniae). In emphysematous cholecystitis (i.e., an acute infection of the gallbladder wall caused by gas-forming organisms), the air is usually trapped in the gallbladder, but it can also be found in the biliary tree. Rarely, air can be found in the biliary tree due to communication with the lungs (i.e., biliary-bronchopleural fistula).

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What are the signs and symptoms of pneumobilia?

Pneumobilia usually has a mild and vague clinical presentation. Individuals may experience nausea and diffuse abdominal discomfort, occasionally followed by vomiting. Many people experience pain in the right upper quadrant, which may be confirmed during the physical examination as right upper quadrant tenderness. 

How is pneumobilia diagnosed?

A detailed analysis of history and physical findings must be completed before proceeding with further diagnostic testing. Ultrasonography is very sensitive in detecting pneumobilia and will identify pneumobilia as multiple highly reflective areas in the liver, described as having a striped appearance. Pneumobilia may appear on plain supine abdominal X-ray with an air bubble accumulation in the intrahepatic bile ducts and the common bile duct, thereby creating the saber sign (i.e., sword-shaped lucency in the right paraspinal region present in about 50% of individuals with pneumobilia). 

On CT scans, pneumobilia is generally seen as a branching pattern of air. Additionally, the presence of oral contrast in the biliary duct may also support the diagnosis of pneumobilia. The use of IV contrast can assist in localizing the identified air bubbles. A CT scan can additionally suggest an etiology to the presence of pneumobilia. For example, it may identify biliary stents or the presence of dilated bile ducts, suggesting the possible diagnosis of cholangitis with inflammatory infiltration of the bile duct, or confirm post-surgical anastomosis. Once identified on imaging, pneumobilia must be differentiated from air in the portal vein as both conditions may have a similar appearance on ultrasonography, and therefore, a CT scan with contrast may be necessary to differentiate. 

How is pneumobilia treated

Pneumobilia requires a varied approach depending on the underlying cause. In some cases, conservative management (e.g., watch and wait, treatment of underlying infection) of pneumobilia in hemodynamically stable individuals with isolated pneumobilia and without additional radiologic or clinical findings is an option. If an infection is the cause of pneumobilia (e.g., emphysematous cholecystitis), broad-spectrum antibiotics (e.g., metronidazole, clindamycin) are suggested as first line treatment. However, prompt surgical cholecystectomy with excision of the gallbladder is frequently necessary as pneumobilia can progress quickly to septic shock and death, particularly in the elderly and individuals with diabetes mellitus.

Surgery may be necessary, however, especially in cases of pneumobilia without prior interventions to the biliary system. Surgical repair of any unusual communication of the biliary and GI system is suggested as well as ERCP sphincterotomy to reduce biliary pressure in cases of large air accumulations. Laparotomy (i.e., a surgical incision into the abdominal cavity) can also be performed in more severe cases that cannot be handled conservatively. 

What are the most important facts to know about pneumobilia?

Pneumobilia refers to the presence of air within the bile ducts, gallbladder, or liver. It is typically the result of an abnormal communication between the biliary tract and the intestines, like with biliary-enteric surgical anastomosis, fistula, incompetence of the sphincter of Oddi, or infection by gas-forming bacteria. It can also occur after an ERCP. Pneumobilia usually has a mild and vague clinical presentation with possible diffuse abdominal discomfort and pain in the right upper quadrant. History and clinical findings can point the clinician towards the diagnosis, yet imaging is typically needed to confirm the presence of air within the biliary system. Treatment depends on the underlying cause but can involve medications, like antibiotics, and/or surgical interventions.

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Related links

Anatomy of the abdominal viscera: Liver, biliary ducts and gallbladder
Bile secretion and enterohepatic circulation

Resources for research and reference

Okan, İ., Tali, S., Özsoy, Z., Deniz, Ç., Acu, B., Yenidoğan, E., Kayaoğlu, H. A., & Şahin, M. (2015). The development of pneumobilia after blunt trauma. Ulusal Cerrahi Dergisi, 32(3): 224–225. DOI: 10.5152/UCD.2015.2782

Pneumobilia. In ScienceDirect. Retrieved March 24, 2022, from  

Sherman, S. C., & Tran, H. (2006). Pneumobilia: benign or life-threatening. The Journal of Emergency Medicine, 30(2): 147–153. DOI: 10.1016/j.jemermed.2005.05.016