Aerobilia in a cat with extrahepatic biliary obstruction
I should be doing my accounts but this is really a lot more interesting. A few weeks back I posted a case with gas in the portal circulation. Today’s cat has the other potential cause of gas densities in the liver: aerobilia. This is also not common.
He is a quite poorly little cat with a history of chronic diarrhoea and weight loss. His small intestine has diffusely increased mucosal echogencity. This is duodenum:
oblique view of the cranial duodenal flexure going into the descending duodenum
And the end of the common bile duct as it reaches the papilla is also abnormal. In fact the lumen is almost completely occluded at that point. Further evidence of extra-hepatic biliary obstruction is in the degree of dilation of the more proximal common bile duct:
another oblique view, the common bile duct measures 5.0mm (‘normal’ being something less than 4.0mm)
In video images (this is slowed down and power Doppler used to demonstrate blood flow in surrounding vessels) you can see also see mobile and intensely echoic gas bubbles in the common bile duct.
In a still image:
longitudinal plane view from a right/ventral paracostal position of the porta hepatis. The caudal border of the liver is just visible in the left of the image. The cranial duodenal flexure is immediately caudal to it and is seen in short-axis cross-section. The portal vein lies dorsal to the duodenum and the common bile duct runs between them -coursing somewhat caudally and then turning ventrally to enter the duodenum on its caudal aspect.
Within the liver parenchyma there are also gas bubbles:
It’s not easy to be sure from this image whether they are in portal veins or biliary tracts. However, portal gas tends to get carried peripherally whereas bile flows towards the hilus:
I am presuming that the biliary obstruction in this cat is the result of cholangitis with scarring/swelling/sludging at the papilla. There is no obvious cholelith, mass lesion or pancreatic changes. He may well have concurrent IBD although lymphoma cannot be excluded at this point.
