Which structure will NOT be visualized if there is cystic duct obstruction during hepatobiliary imaging?

In hepatobiliary imaging, particularly using a radiotracer that evaluates the function of the liver and the biliary system, cystic duct obstruction directly impacts the visualization of certain structures. The gallbladder is typically not visualized when there is an obstruction in the cystic duct because this duct is responsible for draining bile from the gallbladder. When obstructed, bile cannot flow into the duodenum, leading to the gallbladder filling with bile that cannot exit, which prevents it from being seen in imaging studies.

In contrast, structures like the common hepatic duct and the common bile duct may still be visualized despite the obstruction, as they are part of the biliary tree where bile can still flow from the liver. The small intestine can also be visualized as it is downstream of the biliary system and does not depend on the gallbladder's function for its own imaging during this type of study. Therefore, it is the gallbladder that will notably be absent from visualization due to the obstruction in the cystic duct.