All Proton treatment patients were encouraged to have a full bladder
during treatment...

Keith Lundy/So. California
40 Proton Beam Radiation Treatments
Loma Linda  Univ.Med Ctr..3/03-5/03

Keith is right. During my EBRT's it was considered highly desirable to have
a full bladder. It helps protect your plumbing and lifts it out of the way.
The trick is to have a full bladder during treatments but not so full that
you're miserable - or worse, have an accident.

Good luck to him,
Larry

The radiologist requested I have a full bladder at the time of the daily
radiation treatments.  I must admit, it was a challenge to coordinate, given
that sometimes the treatments often took place later than scheduled.
Nothing like that feeling of having to go, especially towards the end of
treatment when the plumbing was damaged a bit.

I believe that lots of water is good also for helping the body deal with the
effects of radiation as well as other treatment programs including chemo and
surgery.

Robert

...

...

There are two likely reasons why he has to urinate more
often.

The first is that his prostate is swelling up.  Radiation
causes the prostate to become inflamed/swollen.  The urethra,
the tube leading from the bladder through the penis,
passes through the prostate.  When the prostate swells,
it clamps down on the urethra, making it harder to
urinate.  As a result, the patient often cannot fully empty
the bladder.  He urinates a smaller amount more often.

The second cause is that some of the radiation hits the
bladder itself and irritates the tissues.  The irritation
causes the bladder to send signals to the brain saying
that it's full, time to urinate.  This also increases the
frequency.

Both of these problems eventually clear up by themselves,
but they may get worse until the end of treatment, and then
slowly get better.  In my case, the problem persisted for
about 8 weeks after the end of radiation, then gradually
went away.  By about 12 weeks I was back to normal.

In the meantime, there are drugs that may help.  Ibuprofen
is an anti-inflammatory that may slightly ease the swelling
of the prostate.  Flowmax (that's a trade name, I forget
the generic name) can also assist.  But the patient
should not take either of those without consulting with
the doctor.

I found it helped to keep a urinal or a jar by the bed so
that I could get up in the middle of the night, urinate into
it, and go right back to sleep.  It was less disruptive than
going to the bathroom 6 times each night.

   Alan