About bowel problems after pelvic radiotherapy

Sometimes pelvic radiotherapy can cause long-term changes to the way the bowel works. These changes may start during treatment and not get better. Or the changes may develop months or years after treatment.

Bowel problems can be embarrassing and difficult to talk about. But if you are affected, it is important to talk to your doctor. 

There are lots of ways of managing or treating bowel symptoms. Your doctor can advise you. Or they may refer you to:

  • a specialist in bowel problems (a gastroenterologist)
  • a specialist nurse or physiotherapist who gives advice on problems with bowel control (a continence adviser).

Tests to check for bowel problems

You may have tests to find out what is causing your symptoms. Tests can include:

  • Blood and stool tests

    You may have a sample of blood taken to be tested in a laboratory. You may also be asked to collect a sample of your poo (stool).

  • X-rays and scans

    X-rays and scans can be used to look inside your body.

  • A colonoscopy or sigmoidoscopy

    A doctor or nurse passes a scope (a thin tube with a light and tiny camera on the end) into the bowel to look for any abnormal areas.

  • A gastroscopy

    A doctor or nurse passes a scope into the mouth and down into the upper part of the small bowel to look for any abnormal areas.

  • Breath tests

    Doctors use samples of your breath to investigate symptoms such as diarrhoea or discomfort in your tummy (abdomen).

Treating bowel problems after pelvic radiotherapy

We have more information about treating the following bowel problems after pelvic radiotherapy:

We also have information about coping with bowel changes that may be helpful.

Diet and bowel problems

You may improve some bowel problems with your diet and what you drink.

It is important to try to eat at regular times. This helps to encourage a regular bowel pattern. Skipping meals may make your symptoms worse.

You may notice certain foods make your stools loose or increase wind. If you experience this, you may want to try eating less of these foods without cutting them out altogether. It is best to do this with the support of a dietitian. This is because it is important to continue to eat a wide range of different food types.

Your doctor can refer you to a dietitian for expert advice on managing your diet. The dietitian may ask you to keep a note of all the food you eat for the 7 days before you see them. This is called a food diary or dietary diary. It lets them see the types of food you usually eat.


Aim to drink at least 1 to 2 litres (2 to 3.5 pints) of fluids a day. Water is best. Drink smaller amounts through the day rather than large amounts of fluids with meals. For some people, fizzy drinks, caffeinated drinks (like coffee, tea or cola) and alcohol can make bowel problems worse. You may want to limit how much of these you drink.


Changing how much fibre you take may help with some bowel problems. This may mean increasing or decreasing the amount of fibre in your diet.

There are two types of fibre:

  • Insoluble fibre
    Insoluble fibre helps with managing constipation, and it can also help with other bowel problems. You can get insoluble fibre from bran and seeds. It is also in multigrain, wholemeal and wholegrain foods, such as bread and cereals.

  • Soluble fibre 
    Soluble fibre helps bulk up and slow down bowel movements, so it may help improve diarrhoea or soft stools. You can get soluble fibre from oats and bananas, and from apples and pears with their skins removed. It is important to remove the skins, because they contain insoluble fibre.

Your doctor, nurse or dietitian will give you advice on the type of fibre you need and how much you should have.

If you are adding fibre to your diet, do it slowly. This gives your body time to adjust. Start with small amounts and slowly increase the amount when you are ready. Make sure you drink more water while you are having more fibre.

Adding more fibre will not be right for everyone. Following the ‘5 a day’ plan for fruit and vegetables may not always be appropriate.

Soluble fibre supplements

People with bowel control problems are often prescribed soluble fibre supplements, such as Normacol® or Fybogel®. They work by absorbing water and expanding to fill the bowel. This makes the stools bulkier and easier to push out. But some people find Fybogel makes their bowel produce more wind.

If you are taking fibre supplements, make sure you drink plenty of fluids. You should drink at least 2 litres (3.5 pints) every day.

Food intolerance

Sometimes radiotherapy can affect how well your bowel copes with certain food types, such as lactose. Lactose is found in some dairy products, such as milk.

Symptoms of food intolerance may include tummy cramps, feeling bloated, and having more wind after eating a particular food. If you think you may have a food intolerance, ask your GP to refer you to a gastroenterologist.

Food intolerance may improve over time, so it is worth trying foods again rather than avoiding them for long periods of time.

Uncommon and rare bowel late effects

Very occasionally, people may have the following problems because of pelvic radiotherapy:

  • Ulcerated bowel

    An area of bowel tissue may break down (ulcerate) and not heal. This can cause watery diarrhoea with blood or mucus in it. It can also cause pain and cramps when you go to the toilet. This may be treated with hyperbaric oxygen therapy.

  • Anal stricture

    Radiotherapy may cause a tight band of scar tissue at the opening of the back passage (anus). This makes the anus narrower. It is called an anal stricture. It can cause difficulty and pain when you try to open your bowels.

    If it is mild, your doctor will advise you to take a stool-softening laxative or fibre supplement. This will make it easier to go to the toilet, which will help stretch the stricture. If the narrowing is more severe, your doctor may refer you to a bowel specialist. You may be able to have a procedure to stretch the opening. This is called dilatation. Or you may have an operation under general anaesthetic to cut through the scar tissue. Your doctor or specialist nurse can explain more about these treatments.

  • Bowel blockage

    Signs of a blockage (obstruction) in the bowel may include:

    • being unable to pass wind
    • constipation
    • tummy pain
    • feeling sick or being sick (vomiting).

    A bowel blockage is usually treated with fluids through a drip to let the bowel rest. Some people also have treatment for constipation. If the bowel continues to be blocked, some people may need an operation to remove the blockage.

  • Perforated bowel

    Very rarely, a hole may develop in the bowel wall. This is called a perforated bowel. It can make you feel suddenly unwell. This is usually treated straight away with an operation to remove the affected part of the bowel.

  • Fistula

    fistula is an abnormal opening that forms between 2 parts of the body. Rarely after pelvic radiotherapy, an opening can develop between the rectum and vagina or the rectum and urethra.

    Having a biopsy (removing a tissue sample) of the rectum after brachytherapy for prostate cancer may make a fistula more likely.

    Sometimes a fistula will close on its own. It can then be managed with treatment to control symptoms. If this does not happen, it may be possible to have an operation to close it.

  • Effects on nerves (lumbosacral plexopathy)
    • Very rarely, radiotherapy may affect the nerves in the pelvis. This may cause:
    • leg weakness
    • changes in sensation, including tingling and numbness
    • changes in how the bladder or bowel work.

    Tell your doctor if you notice this. They may do some tests to find out what is causing the changes. Physiotherapy may help to improve some symptoms.

Good toilet habits for bowel control

Learning these toilet habits can help with problems such as constipation or straining on the toilet.

Toilet routine

Most people find the best time to empty their bowel is about 30 minutes after a meal. But this can vary. You may already know what time works best for you.

Straining to try to pass a stool can weaken your pelvic floor muscles. This can cause problems with bowel control in the future. If you have to wait for a long time after sitting on the toilet, you may be going to the toilet too soon. Or it may be a sign that you are constipated.

Try to not go to the toilet until you have a strong urge to poo (pass a stool).

Toilet posture

Sitting in the right position on the toilet can help you to empty your bowels better. Lean forward a little and rest your elbows on your knees. Use a small footstool to raise your feet off the floor by about 20cm (8 inches). This will make your knees higher than your hips.

Do not strain or hold your breath. Straining or holding your breath makes the muscles tighten instead of relaxing them so you can pass stool. You may find using a relaxed breathing technique helps.

The correct position for emptying your bowels

If you have had recent hip surgery, do not use this position. Always check with your doctor first.