Jerry @jerrydrennan
Staging can be a confusing concept. Simply put, staging is a set of tests done to find out how much cancer is in the body and where it is. Your cancer team will gather lots of different information to determine the stage from tests like:
- blood tests
- imaging studies: like CT scans, MRIs or ultrasounds are a few example of common imaging studies. Cholangiogram is a special imaging test that looks at the bile ducts to see if they are blocked, narrowed, or dilated (widened)
- biopsy: this is when a tissue sample is taken from the gall bladder to examine the cells under a microscope

You mentioned that you have perihilar bile duct cancer. That means is started in the hilum, the area just outside the liver. You also said you have stage 1, which means that the cancer has grown into deeper layers of the bile duct wall, such as the muscle layer or fibrous tissue layer but that it has not spread to nearby lymph nodes or to other parts of the body.

According to the American Cancer Society's website "For some people with unresectable intrahepatic or perihilar bile duct cancers, removing the liver and bile ducts and then transplanting a donor liver may be an option. In some cases it might even cure the cancer."
You can read more here: https://www.cancer.org/cancer/bile-duct-cancer/treating/surgery.html

Does this help explain the staging process? Since you have already been told that you have stage 1, what other staging tests do you have to have?