Bowel and Bladder Preparation for Radiotherapy to the Pelvis

The organs within your pelvis, for example the cervix and uterus (female) or prostate (male), will naturally change position, depending on how full your rectum (bowels) and bladder are.

In order to give radiotherapy directly to the identified area, it is important that this area is in the same position for all your treatments, as it was for your CT planning scan. The most effective way to ensure this is for you to have an empty rectum and a full bladder for each appointment.

When you fill your bladder with water it stretches and moves up and away from the treatment area which decreases the amount of your bladder in that zone. Having a full bladder also helps to push your small bowels up and away from the treatment area which reduces potential side effects on them.


A week before your CT/MRI planning appointment, start drinking fluids regularly throughout the day. Maintain an intake of at least 1.5L per day (preferably water). This will ensure you remain well hydrated throughout treatment, to be able to achieve a consistently full bladder during preparation for each treatment session. Practicing to hold urine in your bladder for a period of time at home will help you prepare for your radiotherapy sessions with full bladder.

It is important to reduce your intake of tea, coffee and alcohol as they can make you go to toilet more often and can dehydrate you. Try decaffeinated tea and decaffeinated coffee instead. If you have a hard time drinking plain water try flavouring it (mint, lemon juice…)

At your radiotherapy planning CT appointment, and each day before treatment, we will ask you to empty your bladder. We will then ask you to re-fill your bladder by drinking a specific amount of fluid. Please make sure that you are well-hydrated when you come for the planning scan, as well as when you come for your radiotherapy. You will need to wait while your bladder fills up before the treatment is given. The amount of fluid you need to drink and the length of time you then need to wait will be confirmed during your first appointment for the planning CT.

The appointment times you are given for your radiotherapy are the times at which you will need to be ready for treatment. You will need to arrive 30-40 minutes earlier than this in order to prepare your bladder as described above.

Try to keep your bladder full for treatment, but if you are unable to hold your water, speak to one of the radiographers at your treatment machine. They will ask you to empty and give you a time at which to start re-filling your bladder.


If you have regular (daily) bowel movements, you do not need to do anything different, as your bowels should be fine for the CT planning scan and radiation treatment.

  • Avoid food or drink that may give you gas.
  • Eat regularly – skipping meals and not eating can lead to increased full­ness of your rectum and increase wind in your bowels.
  • Exercise regularly – gentle exercise such as walking and stretching can help move wind and regulate your bowel movements.
  • Avoid swallowing air when you eat:
    • Eat slowly and chew food well
    • Chew with your mouth closed
    • Avoid chewing gum
    • Sip drinks rather than gulping
  • Avoid or reduce the amount of foods you eat that can cause wind or bloating such as:
    • Some vegetables (cabbages, sprouts, broccoli and cauliflower)
    • Dried fruits (especially in muesli or similar cereals)
    • High fat and greasy foods
    • Onions, lentils and beans (including baked beans)
    • No more than two pieces of fruit a day
    • Very spicy foods
    • Carbonated drinks (soft and alcoholic).

If you do not have bowel movements every day, or if you have constant problems with gas in your bowels, please talk to your doctor, you may need to be given laxatives or enema.


  • Have a light breakfast, but do not eat anything for two hours before your appointment.
  • Remember to drink plenty of clear fluids.
  • Try to have a bowel movement, without straining, before your appointment (we will ask you about this).
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