Type 3a cholangiocarcinoma is characterized by its location in which area?

Type 3a cholangiocarcinoma is primarily characterized by its location at the hilum, which is the area where the bile ducts converge, and extends into the right hepatic duct. This localization is significant because it often leads to obstructive jaundice due to the tumor's effect on bile flow. The involvement of the hilum is critical, as it can affect both left and right hepatic duct drainage, typically causing more extensive implications for liver function and necessitating careful surgical planning.

In contrast, the other options describe locations that are not representative of type 3a cholangiocarcinoma. The hepatic flexure is related to the colon and not relevant to bile duct pathology. Restricting the location to only the left hepatic duct or solely the common bile duct does not capture the full extent of the tumor's impact, which encompasses both sides of the hepatic duct system at the hilum, thus making option B the most accurate representation of this type of cholangiocarcinoma.