North American Veterinary Licensing Examination (NAVLE) Practice Test

Which normal anatomic feature may predispose cats to extrahepatic biliary obstruction?

1. Narrowing of the duodenum distal to the entry of the common bile and pancreatic ducts

2. Common opening of the pancreatic and common bile ducts into the duodenum

3. Enlarged duodenal papilla compared to other species

4. Decreased diameter of gall bladder wall muscle fibers

The correct answer is: Common opening of the pancreatic and common bile ducts into the duodenum

The correct answer identifies that the common opening of the pancreatic and common bile ducts into the duodenum can predispose cats to extrahepatic biliary obstruction. This anatomical arrangement means that any condition affecting the duodenum, such as inflammation or obstruction, can simultaneously affect both the biliary and pancreatic secretions. Anatomically, cats have a unique configuration where both ducts open at the same site, which raises the likelihood of one duct's dysfunction impacting the other. If, for instance, there is swelling or a pathological process at the site of the common opening, it can lead to obstruction of both bile and pancreatic secretions, resulting in extrahepatic biliary obstruction, which is a critical concern in feline medicine. Other features discussed, such as the narrowing of the duodenum or the diameter of gall bladder wall muscle fibers, do not present the same level of risk for obstructing the biliary flow directly due to their anatomical and physiological roles. Additionally, while the enlarged duodenal papilla compared to other species might be an interesting observation, it is not inherently linked to an increased risk of obstruction in cats specifically. Therefore, the unique anatomical feature of the common duct opening plays a crucial role in understanding the predisposition to biliary