Managing other late changes to the bowel after radiotherapy

Radiotherapy can sometimes affect blood vessels or muscles inside your bowel or inside the skin around the back passage (anus). Bowel changes aren’t always due to radiotherapy. If you have any bowel changes, always get them checked by a doctor.

Bleeding from the back passage is common after radiotherapy but is usually mild and doesn’t need treatment. If bleeding causes problems, the most common treatment is with drugs given into the bowel. Occasionally, other treatments are used. For example, heat may be used to seal blood vessels or oxygen therapy used to help tissue heal.

Some people get bowel cramps and feel they need to go to the toilet although their bowel is empty. This is called tenesmus. Treatments include soluble fibre, low dose anti-depressants and exercises to strengthen the muscles used in bowel control.

After radiotherapy, some people develop a split in the skin of the anus. This is called a fissure. Your doctor may prescribe creams for this and give you advice about avoiding constipation. Some people are treated with injections or a small operation.

Bleeding from the bowel

Bleeding from the back passage (rectum) after radiotherapy is common, but it is usually mild and often doesn’t need treatment. Bleeding sometimes improves gradually and can stop on its own after a few years.

Bleeding may not always be caused by the radiotherapy. It can be caused by piles (haemorrhoids) or straining on the toilet. But even if you think you know the cause, always tell your cancer doctor or nurse specialist if you have any bleeding from the back passage. It is important to find out the cause and to rule out serious problems. Your doctor will do an examination of your back passage and may refer you to have a test to look at the inside of your rectum (an endoscopy).


If there is only a small amount of blood and you are finding it manageable, you probably won’t need any treatment. You will be given advice about your bowel habits to help minimise the bleeding and avoid constipation. If you are taking blood-thinning drugs, your dose may be reduced and monitored.

If you have heavy bleeding that is interfering with your day-to-day life or if you become anaemic (have a lack of red blood cells), you are likely to need treatment. Your doctor or specialist nurse will explain more about your treatment options and give you more detailed information.

The most commonly used treatment for bleeding from the back passage is a drug called sucralfate (Antepsin Suspension®). It is given as an enema. This is when a fluid (usually medicine) is gently infused into your back passage through a short tube. Sucralfate works by coating the lining of the rectum. This reduces inflammation and encourages healing. It is important to avoid getting constipated when you are being treated with sucralfate.

A drug called formalin is also helpful for some people. It works by sealing the bleeding blood vessels. Your doctor can give it to you using an endoscope, which is passed into the bowel. You can have this done under a general anaesthetic.

If the bleeding is higher up in the large bowel (colon), or if enemas don’t reduce the bleeding, other treatments may be helpful:

  • Argon plasma coagulation directs heat at areas that are bleeding. The heat seals the blood vessels and destroys damaged tissue. It’s given during a colonoscopy (where a doctor passes a thin, flexible tube with a light into your back passage). Doctors don’t yet know how successfully this treats heavy bleeding. There is also a risk that it can cause complications, such as serious tissue damage. Your doctor will discuss this with you.
  • Hyperbaric oxygen therapy works by increasing the amount of oxygen that gets to tissue that’s been damaged by pelvic radiotherapy. This can encourage new blood vessels to grow and may help the tissue heal. Treatment takes up to eight weeks. This treatment isn’t widely available, so you may need to travel some distance for it.


Tenesmus is the feeling that you need to go to the toilet although your bowel is empty. It can involve straining, pain and cramping. It can be caused by cramp (spasms) in the muscles that stimulate the bowel.

The spasms can often be controlled by:

  • pelvic floor exercises
  • taking soluble fibre to bulk up the stool
  • very low doses of certain anti-depressant drugs.

Sometimes tenesmus can be caused by constipation. It’s also sometimes caused by a non-cancerous growth (a polyp) in the bowel, or it can be caused by a cancer.

If you have tenesmus, your doctor will examine your back passage and may arrange for you to have a test called a flexible sigmoidoscopy. This looks at the rectum and the lower part of the large bowel.


After radiotherapy, some people develop a split in the skin of the anus. This is called a fissure. It can cause a sharp, intense pain when you pass a stool (bowel motion).

Your doctor can usually prescribe creams to apply to the area that will help. It’s important to avoid getting constipated, because this can make a fissure worse. Your doctor may also prescribe a laxative to make it easier for you to go to the toilet.

If the fissure doesn’t get better, your doctor may advise treating it with injections of botulinum toxin A (Botox). These are given into the tissue lining the anus.

Some people may need a minor operation to make a small cut in the muscle surrounding the anus. This releases the tension in the muscle and allows the fissure to heal. You usually have this operation under a general anaesthetic, and it can be done as a day patient.

Back to Long-term and late effects

Changes in how your bowel works

Treatment for rectal cancer may lead to changes in how your bowel works. These can usually be managed successfully over time.

Managing bladder problems

There are ways to manage changes in the way your bladder works. It’s important to talk to your doctor if you’re having problems.