The rectum being “empty” didn’t mean it had to be clean like it is for a transrectal biopsy; my radiation oncologist (RO) told me there was no need for an enema.

He told me what they mean is nothing in the lower intestine, material or gas, that might move during the treatment and cause the prostate to move: no foods that might cause gas. (At 65y/o at the time, I knew which foods would cause me gas and which wouldn’t; it was fairly easy to manage.)

So, at the same time as emptying my bladder 45 minutes prior to treatment, I would also empty bowels. Worked every time; never had a problem. (I had 28 proton radiation treatments.)