You might need to change what you eat after treatment for anal cancer. 

You'll find that your digestion takes time to settle down after anal cancer treatment. Some foods can upset the way your bowel and anus works. After treatment, high fibre foods, such as fruit and vegetables, may give you loose poo. You may need to go to the toilet much more often than normal.

Diet after surgery

Any changes needed in your diet will depend on the type of operation you've had.

If you've had surgery to remove your anus and rectum, you won't be able to eat immediately after your operation. But by the time you go home, you should be able to eat a regular diet. Your stools may be less solid if the surgeon removed part of your bowel. The bowel absorbs water as stool passes through it, so having less bowel means less water will be absorbed.

There's nothing you absolutely cannot eat. You may also find that what upsets your tummy at first is fine a couple of months later. So, if you do have difficulty with certain foods, avoid them for a while and try again later.

Foods that can cause wind

Some foods can cause wind, which is hard to control when you have had a colostomy. You might need to experiment to find out which foods upset your system. Foods that often cause problems with wind include:

  • high fibre fruits and vegetables
  • onions and cabbage
  • fizzy drinks and beer
  • rich or fatty foods

Seeing a dietitian

If you are having problems, your hospital can refer you to a dietitian, who can help you work out a diet that suits you. You might also find it useful to keep a food diary before you see them. A food diary is a record of:

  • what you eat
  • when you eat
  • any digestive problems you have, and when you have them

Keeping a food diary over a week may spot foods that are causing you problems. You can then cut them out of your diet.

Diet after radiotherapy

Radiotherapy for anal cancer often causes frequent bowel movements. This is because the rectum gets irritated and inflamed, and you might need to open your bowels urgently. The frequent bowel movements usually settle down about 3 to 4 weeks after the radiotherapy has finished but it may continue for some people.

Your doctor can prescribe medicines to reduce the inflammation. If the problem is severe, you may need steroid enemas. You squeeze a small amount of steroid liquid into the bowel to reduce inflammation. 

While you recover from radiotherapy treatment, it might help to stick to a low fibre diet.

A low fibre diet means: 

  • cutting out whole grain cereals and wholemeal bread
  • avoiding fibrous vegetables, fruit and fruit juice

Over time, you can start eating the high fibre foods you cut out before. Some people also avoid alcohol as they find it makes their bowel symptoms worse.

Diet after chemotherapy

Chemotherapy for anal cancer can give you diarrhoea and might make you feel sick. These side effects will disappear after your treatment is over. Over time, you will be able to get back to a regular diet.

You are likely to have a combination of chemotherapy with radiotherapy. This can make the side effects harder to cope with. Speak to your specialist nurse or doctor if this happens. They can suggest ways to reduce any unpleasant side effects.

Last reviewed: 
07 May 2019
  • Anal cancer: ESMO-ESSO-ESTRO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    R. Glynne-Jones and others.
    Annals of Oncology 2014. Volume 25, Pages iii10-iii20


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