These images of the liver were obtained from an asymptomatic nephrology clinic patient while trying to find the IVC. What are the white things? Don’t they look like air bronchograms in a consolidated lung? The moving white things indeed represent air. This patient had a history of liver transplant and review of prior imaging showed persistent Pneumobilia. Note the CT images. No further action was taken.

Pneumobilia is accumulation of air in the biliary tree, typically seen after recent biliary instrumentation such as ERCP or percutaneous cholangiography. Can also be seen in transplanted liver as in our patient, incompetent sphincter of Oddi (e.g. following passage of a gall stone), gall stone ileus, ampullary cancer, gall stone ileus and rarely in infection (cholangitis).

On the other hand, portal vein gas usually is seen in sicker patients such as those with ischemic bowel, perforated peptic ulcer, necrotic colorectal carcinoma and intra-abdominal sepsis from pancreatitis, appendicitis, diverticulitis etc. Sometimes, may be seen after procedures such as colonoscopy, gastric dilatation, and umbilical vein catheterization. Gas within the biliary tree tends to be more central while the portal vein gas is more peripheral.

Below are two classic examples that show air bubbles moving within the portal vein in addition to surrounding liver. One of these patients had necrotizing pancreatitis and the other had ischemic colitis.

Lets compare air in the liver and hepatized lung side-by-side: