I had 37 sessions of RT to prostate&pelvis (there was slight spread to seminal vesicles). The actual RT all ok and luckily I live a short distance from the treatment centre.
Where I had my treatment (Clatterbridge) their policy,for me anyway, was mini enema on arrival, empty bladder then about 15-20 mins before the session, they advise when, have 3 cups water. That wasnt bad at all really. Not all treatment centres work that way but they will give you good advice.
For me, they said to continue with normal diet tho maybe cut down on some veg etc that produce most wind, their comment was often the change in diet affects things more. Again they'll advise if necessary.
After a few sessions tiredness came into play for me and some bladder urgency.
Bowels were fine for a good while but maybe 12 months after the 37sessions, had bowel urgency for a while and depite trying to be 'empty' before going for a walk etc soiled myself a handful of times, not a great feeling but one accepts its temporary (& was expected).Immodium worked well when out for the day.
Many have discomfort with full bladder etc for the RT session, the radiographers have seen it all before and will always help.
Peter