Treatment for bowel cancer or pelvic radiotherapy for other cancers can cause long-term changes to the way the bowel works. There are lots of ways of managing or treating bowel symptoms.
If you have a bowel control problem, you may have:
difficulty controlling when and how often you pass stools (poo) or wind
problems controlling your bowel, leading to leakage or soiling, cramps, or bloating
diarrhoea or constipation
difficulty emptying your bowel completely.
Not feeling in control of your bowel can be stressful, particularly when you are away from home. Although you might find it difficult to talk about bowel control problems, it is important to tell your doctor or specialist nurse. There are many things that they can do to help.
Your doctor or specialist nurse will probably have helpful suggestions. The most common ways of improving bowel control include:
changes to your diet
drugs to regulate your bowel
exercising and strengthening the muscles used for bowel control.
If your symptoms do not improve, you can ask your GP to refer you to a continence adviser or a doctor who treats problems with the digestive system (gastroenterologist).
Your doctor or nurse will usually ask about your bowel problems and things that affect your symptoms. It is important that they properly assess your situation. Treatments for bowel control problems depend on your symptoms and what is causing them.
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 stool (poo) loose or increase wind. 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 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 food and symptom diary. It lets them see the types of food you usually eat and what changes may help your symptoms.
Try to drink at least 1 to 2 litres (2 to 3 ½ pints) of fluids a day, unless your healthcare team tells you differently. Water is best. Drink small amounts throughout the day so you do not drink lots of fluids with meals. Some types of drink can make bowel problems worse. You may want to limit drinking:
fizzy drinks
caffeinated drinks such as coffee, tea or cola
alcohol
sugar-free drinks that contain artificial sweeteners.
Fibre
Changing the amount of fibre in your diet may help with bowel problems. Your GP, cancer doctor, nurse or dietitian will give you advice about the type of fibre you need and how much you should have. This depends on the treatment you have had and the type of bowel problem.
There are 2 types of fibre:
Insoluble fibre helps with managing constipation. It can also help with other bowel problems. You can get insoluble fibre from wholegrain bread and cereals, vegetables and fruit skins. It is also in bran and seeds.
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.
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. Fibre absorbs fluid, so make sure you also drink more water. This helps stools stay soft and move through the bowel easily.
Adding more fibre is not right for everyone. Following the 5-a-day plan for fruit and vegetables may not always be right for you. Your doctor, nurse or dietitian may give you advice about blending, slow cooking, and peeling fruit and vegetables to reduce the amount of fibre you have.
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 stool bulkier and easier to push out. But some people find Fybogel® makes the bowel produce more wind.
If you are taking fibre supplements, make sure you drink plenty of fluids. You should drink at least 2 litres (3½ pints) of fluids every day.
Food intolerance
Sometimes radiotherapy can affect how well your bowel copes with certain food types, such as lactose or fructose. Lactose is found in milk and some other dairy products. Fructose is found in sugar and fruit.
Symptoms of food intolerance may include:
tummy cramps
feeling bloated
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.
It is important to speak to a doctor or specialist nurse before taking any medicines.
The most commonly used treatment is loperamide. It slows down your bowel, making stool more solid and less frequent. Taking loperamide regularly can work very well for some people. It usually works best when taken about 20 to 30 minutes before eating a meal. Always take medicines exactly as your cancer team, GP or pharmacist explains.
It is safe to take loperamide for as long as you need it. But you should discuss this with your doctor.
The dose of loperamide you take may need to be adjusted until you find what works best for you. Your doctor may recommend starting with a low dose and increasing this until your symptoms are controlled. Loperamide is available as a syrup, which allows you to make small changes to the dose as needed.
Sometimes loperamide can cause cramps. If this happens, taking a lower dose may help.
Other types of anti-diarrhoea medicine include codeine phosphate and diphenoxylate (Lomotil®). Your GP, cancer team or a continence adviser can give you advice.
Drugs that can increase bowel symptoms
You may be taking medicines that can make bowel symptoms worse:
Magnesium in antacids – this treatment for heartburn may cause diarrhoea.
Proton pump inhibitors such as omeprazole (Losec®) may cause wind and diarrhoea.
Laxatives such as Lactulose® and Fybogel® may cause wind and diarrhoea.
Metoclopramide – this anti-sickness drug may cause diarrhoea.
Metformin – this tablet to treat diabetes may cause diarrhoea, particularly when you have just started taking it.
Beta-blockers – these tablets to treat high blood pressure and some heart problems may cause diarrhoea.
If you think a drug you are taking might be making your symptoms worse, tell your doctor. They may be able to prescribe a different drug that may affect you less.
If you have problems with constipation or difficulty emptying your bowel completely, you may be given 1 of the following treatments:
Soluble fibre supplements, such as Fybogel® or Normacol®.
Suppositories – you put these into your rectum (back passage) or stoma. As they dissolve, they release a lubricant. This encourages the bowel to empty. They usually take about 10 to 30 minutes to work. It may be easier to use them when you are able to stay near a toilet for a while after inserting them. You may not need to use them every day. Ask your doctor or nurse if you want to try using them at night so they have longer to work.
Enemas – these contain a small amount of gel or liquid that you squeeze into the lower bowel. This stimulates the bowel to empty.
Drugs that can cause constipation
Your doctor can check whether you are taking any drugs that may cause constipation. They may be able to prescribe a different drug.
If you have problems with urgency, loose stools or bowel incontinence, smoking or vaping may make things worse. This is because nicotine stimulates the bowel. Talk to your doctor about ways to stop smoking or smoke less.
To avoid putting extra pressure on your pelvic floor muscles, try to keep your weight within healthy limits. You can also look after these muscles by avoiding getting constipated and not doing heavy lifting.
Some bowel control problems can make it difficult to know when you will need the toilet. This can be very stressful. You may worry that you will not be able to ‘hold on’. Or you may be checking all the time for signs that you need to go.
A continence adviser may suggest a bowel retraining programme to help you feel more in control. This teaches you ways to:
resist the urge to go straight away
get your bowel habits into a regular, predictable pattern
manage any anxiety you have about bowel control.
Bowel retraining may also involve taking anti-diarrhoea medicines and doing pelvic floor exercises.
If you have ongoing problems with constipation or difficulty emptying your bowel, good toilet habits can help.
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. It is important not to push hard to try to pass stools. This can weaken your pelvic floor muscles and may cause problems with bowel control in the future.
If you have to wait for a long time on the toilet, you may be going to the toilet too soon. Or it may be a sign that you are constipated. Try not to go to the toilet until you have a strong urge to pass a stool. And try not to sit on the toilet for more than 20 minutes.
Toilet posture
Sitting in the right position on the toilet can help you to empty your bowel. 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 stools. You may find using a relaxed breathing technique helps.
The correct position for emptying the bowel
Image: The illustration shows a side view of a person sitting on a toilet. The person is leaning forward slightly, resting their elbows on their knees. Their feet are on a block so that the knees are higher than the hips.
If you have had recent hip surgery, do not use this position. Always check with your doctor first.
About our information
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer.
References
Below is a sample of the sources used in our late effects of pelvic radiotherapy information. If you would like more information about the sources we use, please contact us at informationproductionteam@macmillan.org.uk
S Haas, A Højer Mikkelsen, C Jensenius Skovhus Kronborg et al. Management of treatment-related sequelae following colorectal cancer. PubMed. Colorectal Disease Journal.15 August 2022. Available at https://pubmed.ncbi.nlm.nih.gov/35969031/ [accessed March 2026]
V Sun, C Wendal,W Demark-Wahnefried et al. Diet and Behaviour Modifications by Long-Term Rectal Cancer Survivors to Manage Bowel Dysfunction-Associated Symptoms. PubMed. Nutrition and Cancer. 2020 January. Available at www.ncbi.nlm.nih.gov/pmc/articles/PMC6456395/ [accessed March 2026]
A Carlile and T McAdam. The Long-Term and Late Effects of the Diagnosis and Treatment of Colorectal Cancer. Ulster Medical Journal. 2023 May. Available at https://pubmed.ncbi.nlm.nih.gov/37649914/ [accessed March 2026]
R Dalsania, K Shah, E Stotsky-Himelfarb, S Hoffe et al. Management of Long-Term Toxicity from Pelvic Radiation Therapy. Gastrointestinal cancer- Colorectal and anal. Ascopubs April 2021. Available at https://ascopubs.org/doi/pdf/10.1200/EDBK_323525 [accessed March 2026]
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