Changes in how your bowel works

Treatment for rectal cancer can cause changes to the way the bowel works. These changes usually become less troublesome with time. But for some people, bowel changes continue for several months or more. This can take time to adjust to and there are ways to help manage the changes.

Bowel changes may include:

  • diarrhoea or loose stools
  • bile acid malabsorption
  • feeling the need to rush to the toilet (urgency)
  • leakage (faecal incontinence)
  • constipation
  • wind and bloating.

Possible changes to the bowel after pelvic radiotherapy may also include:

  • bleeding from your back passage
  • food intolerance
  • small bowel bacterial overgrowth.

It’s important to tell your doctor if you have problems with your bowel. They can give you advice and do tests to find the cause. Some people may be referred to a bowel specialist (a gastroenterologist).

Treatment depends on the symptoms you have and what is causing them. Changes in diet, anti-diarrhoea drugs and exercises that strengthen the muscles used for bowel control may all help manage bowel problems.

Bowel changes

Most people have changes in how their bowel works following surgery and/or radiotherapy for rectal cancer.

You may find your bowel habits don’t go back to the same as they were before treatment. It may take at least a year for things to settle down. Over time, bowel symptoms usually become less troublesome. Most people find they get into a new routine that becomes normal for them.

If bowel problems don’t settle, there are many things that can be done to help. Your doctor or nurse can give you advice. They may also refer you to a specialist in bowel control problems for further assessment and treatment.


Changes after surgery

After bowel surgery your large bowel is shorter than before. This means bowel motions (stools) pass through more quickly. This often settles as your body adjusts. But if part of the rectum has been removed, there may be long-term changes to how your bowel works.


Changes caused by a shorter bowel

You may find stools pass through the bowel more quickly and are softer and looser, or liquid. You may go to the toilet more often and more urgently.

Softer stools can be more difficult to pass out of the bowel completely. This can mean needing to go back to the toilet a few times after a bowel movement to finish passing the stool. Stools may be stickier. You may need to wipe around your back passage more after passing a stool. This can sometimes make the skin in the area sore.

Some people go between having loose stools and constipation. Or, you may feel bloated at times and have problems with wind.

Other changes after rectal surgery

The rectum is the part of the large bowel that stores stool. It has nerves and muscles that help you to hold onto stools until you’re ready to pass them. After surgery these nerves may be more or less sensitive, and the muscles may be weaker. This means you cannot hold onto stools as well as before.

You may feel you need to rush to the toilet (urgency) when you feel you need to pass a bowel movement. Some people may have some leakage from their bowel. Or, there may be occasions when you aren’t able to get to the toilet in time. This is called faecal incontinence.

You may also have less control over when you pass wind. Some people may find it difficult to tell the difference between wind and stool in the back passage. They may leak some stool from the bowel (incontinence) when they pass wind.

It may take up to two years after rectal surgery that involves re-joining the bowel before your bowel is working at its best.

During surgery to remove the rectum, the surgeon may make an internal pouch from a piece of bowel. This acts as a store instead of the rectum. If you have an internal pouch you may not have problems with urgency. But you may find it more difficult to empty your bowel completely. This can sometimes lead to constipation.


Problems with a stoma

If you had a stoma as part of your surgery, it can take some time to adjust. You may have loose stools, or go between loose stools and episodes of constipation. You may also be more aware of wind produced by your bowel. Some people find it difficult to predict when the stoma is going to be active.

Many of our suggestions for bowel function problems are also relevant to people with a stoma. We’ve also included other information specific to coping with a stoma where we think this may be helpful.


Possible changes to the large bowel after pelvic radiotherapy

Radiotherapy to the bowel (pelvic radiotherapy) can cause scarring (fibrosis) in the lining of the large bowel. This makes the bowel lining thicker and less flexible. As a result it cannot hold as much and stools pass through the bowel more quickly. The nerves and muscles that help you hold stool in the rectum can also be affected.

These changes cause similar symptoms to those we mention for bowel surgery (see above). You may have loose stools, or more frequent bowel movements. Or, you may feel the need to rush to the toilet to move your bowels. Some people may have leakage (incontinence). This can vary from slight staining to occasionally a larger amount of stool.

Bleeding from your back passage is also quite common. Radiotherapy can make small blood vessels in the bowel lining fragile so that they bleed. This is usually mild and doesn’t need any treatment. Bleeding can also be caused by piles (haemorrhoids) or straining when you go to the toilet.

Even if you think you know the cause, always tell your cancer doctor or nurse if you bleed from the back passage. It is important to rule out serious problems.

Bleeding caused by radiotherapy may not need any treatment. It may improve gradually on its own. The most common treatment is a drug called sucralfate (Antepsin Suspension). You have this as an enema.

We have more detailed information on managing the late effects of pelvic radiotherapy.


Possible changes to the small bowel after pelvic radiotherapy

As well as its effects on the colon and rectum, radiotherapy can also sometimes affect the small bowel. This may cause one or more of the following conditions:


Food intolerance

Sometimes after radiotherapy for rectal cancer the bowel can’t cope as well with certain types of food, such as:

  • lactose - found in dairy products
  • fructose - a fruit sugar sweetener often found in products labelled ‘no added sugar’
  • gluten – a wheat protein found in breads, cakes, biscuits and pasta.

Symptoms of food intolerance may include tummy cramps, feeling bloated and having wind after particular foods. If you think you may have a food intolerance, ask your doctor to refer you to a gastroenterologist (stomach and bowel specialist).

Bile acid malabsorption

Bile acids help us to digest fats in our food. Pelvic radiotherapy may alter the balance of bile acids in the bowel. This can cause episodes of diarrhoea that come on suddenly.

We have information about how bile acid malabsorption is treated.

Small bowel bacterial overgrowth

The large bowel contains lots of healthy or ‘good’ bacteria that help us digest food. But, a healthy small bowel contains almost no bacteria. After pelvic radiotherapy, extra bacteria sometimes grow in the small bowel This is called small bowel bacterial overgrowth. It can cause a range of symptoms, but the most common one is diarrhoea. Other symptoms include fatty bowel movements( stools), wind, bloating, constipation, feeling sick, vomiting and bad breath.

Small bowel bacterial overgrowth is usually treated with antibiotics.

Back to Long-term and late effects

Managing bladder problems

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