Radiation Therapy to Pelvis: How to Prepare Your Bladder and Bowel

About This Resource

Author: Waterloo Wellington Regional Cancer Program

Revised: September 2024

PEM#: PEMWRHNCC0031

Before Each Treatment

1 hour before: go to the bathroom
Next 30 min: drink your water
Don’t go to the bathroom until after your treatment

Radiation therapy kills cancer cells and stops them from spreading to other areas in your body. You may have side effects where your body is treated with radiation.

When radiation treatment is to your pelvis it can result in side effects to your bladder and rectum. Having a full bladder (feeling like you have to pee) and an empty rectum (daily poo) will help to reduce these side effects.

Before CT Simulation Planning

You have been asked to come one hour before your CT simulation planning appointment in order to get ready for your CT scan.

One hour before your CT scan a Radiation Therapist will meet with you to discuss what you can expect during your CT scan.
At this time you will be asked to empty your bladder (go pee) and empty your rectum (go poo) if you feel you can. Then drink 16 ounces (500 ml) of water.
Please drink all of this water within the first 30 minutes.
After you have finished drinking the water, do not pee until after your CT scan.
You will also be asked about your bowel habits and the last time you emptied your bowels (went poo). Please try to have a bowel movement prior to coming in for you CT scan.
If you do not have a bowel movement daily, please inform the radiation therapist at this time.

Before Daily Radiation Treatment

You will need to have a full bladder and empty rectum each day for your radiation treatment. Prepare your bladder and bowel the same as you did for your CT scan.

Please try to have a bowel movement before coming in for your daily treatment.
One hour before your appointment, empty your bladder and then drink 16 ounces (500 ml) of water or the same amount you had before your CT planning appointment
Please drink all of this water within the first 30 minutes.
Do not pee until after your treatment.
The radiation therapists will make sure your bladder and rectum are the same size as when the CT scan was done. This is to ensure proper treatment.