“Full bladder” isn’t something that’s randomly done, nor is it something that’s to just be “…. encouraged by the techs.”

Coming out of the CT Simulation, you should’ve been informed exactly how many ounces of water to drink (and how many minutes) before each treatment.

(For me, that was just 18oz of water to drink just 30 minutes prior to each session. In the weeks leading up to my radiation treatments, I practiced every day. By the time of my first treatment, I had the routine down to a ritual. I never had problems holding that amount of water. It worked like clockwork every time and never caused an issue.)

It takes time for water you drink to make its way to your bladder - that time is different for each person (and you don’t really have to drink a lot), and should have been figured out at the time of your CT Simulation.

You should work this out with your radiation oncologist (or the nurse practitioner assigned to you), not with the tech guys.

Yes, it is absolutely necessary to have a full bladder during the procedure in order to both push the bladder and small bowel as possible away from the field of radiation and to keep other nearby organs and tissues in that area in the same location for each treatment. This needs to be done consistently and exactly the same way for each session.