Bowel changes after pelvic radiotherapy

The bowel is made up of the small bowel and the large bowel. Sometimes, pelvic radiotherapy can cause changes to the way the bowel works. In some people, these changes will not get better after treatment finishes. Others may not develop until months or years after treatment has finished.

Pelvic radiotherapy can cause scarring (fibrosis) in the lining of the large bowel which can mean solid waste passes through quickly. The muscles that help to hold stool in the rectum may also be weakened. Sometimes, pelvic radiotherapy causes the small blood vessels in the bowel to become more fragile and may cause the bowel to narrow. These changes lead to symptom such as diarrhoea, constipation, leaking (incontinence) or bleeding from the back passage (bottom).

Many bowel problems can be managed or treated successfully. Tell your doctor about any symptoms you are having. They can give you advice and may do some tests. They may also refer you to see a bowel specialist (a gastroenterologist).

The bowel and pelvic radiotherapy

Pelvic radiotherapy can cause changes in the way their bowel works. For some people, these changes start during treatment and don’t get better. But for others, the changes may develop months or years after treatment.

The bowel is part of our digestive system. It’s made up of the small bowel and large bowel The small bowel absorbs nutrients from the food we eat. It then passes the liquid waste into the large bowel (colon and rectum). The colon absorbs water from the waste before passing the more solid waste (faeces or stool) into the rectum. The stool is held in the rectum until it’s ready to be passed through the anus (the opening to the outside of the body).

Possible late effects

The blood supply to the bowel can be affected by radiotherapy, making the bowel tissue and the small blood vessels in it more fragile. This may cause bleeding from the back passage. Radiotherapy can cause scarring (fibrosis) in the large bowel lining, making it thicker and less flexible. This causes solid waste to pass through more quickly than before, so nutrients may not be as well absorbed. The bowel will also be unable to hold as much solid waste (stool). The muscles that help to hold stool in the rectum can also be affected, which may cause problems with bowel control and leakage (incontinence).

Radiotherapy can also cause the bowel to narrow. When radiotherapy affects the small bowel, it can cause food intolerance or conditions such as bile acid malabsorption or small bowel bacterial overgrowth.


The symptoms of late effects to the bowel can include:

  • bleeding from the back passage (bottom)
  • passing mucus (a clear, sticky substance)
  • cramps or spasms in the bowel that may be painful
  • feeling that you haven’t emptied your bowel completely (tenesmus)
  • diarrhoea or severe constipation
  • needing to rush to open your bowels (urgency)
  • leaking or soiling (incontinence)
  • passing a lot of wind.

Some people find that their symptoms don’t cause too many problems, and that they can manage them fairly easily The change in the way the bowel works may be slight, for example, having to go to the toilet twice a day instead of once. But sometimes bowel changes can have a much greater impact, interfering with day-to-day life.

Talk to your doctor

There are lots of ways of managing or treating your symptoms. Your doctor can advise you, or may refer you to a specialist in bowel problems (a gastroenterologist) for tests. You may also be referred to a specialist nurse or physiotherapist for advice on incontinence and treatment (we use the term continence adviser because it’s shorter).

There are three problems you must always talk to your doctor about:

  • Passing blood from your back passage.
  • Waking up from sleep to open your bowels.
  • Needing to rush to open your bowels, or having accidents.

These symptoms may not be due to anything serious, but should always be checked out. They often respond to simple treatments. Occasionally they can be a sign of a more serious problem, so it’s important to find out the cause as soon as possible.


You may have tests to find out the cause of the symptoms. Tests can include:

  • blood and stool tests
  • x-rays and scans
  • Endoscopy –a doctor or nurse passes a thin tube with a light on the end (an endoscope) into the bowel to look for any abnormal areas.

Some people may need to have a sample of tissue removed (a biopsy) from the bowel. This should only be done by an experienced bowel specialist.

Back to Late effects of pelvic radiotherapy

About late effects

Some people may have long term or late effects of pelvic radiotherapy. These can usually be treated or managed successfully.

Bladder changes

Late effects on the bladder can usually be managed or treated successfully. Talk to your doctor about any symptoms.

Late effects and sex life

Pelvic radiotherapy can have some late effects on your sex life. Talk to your doctor for advice on how to manage these.