Bleeding from the bowel after pelvic radiotherapy
Bleeding from the rectum
Bleeding from the rectum (back passage) is common after pelvic radiotherapy. Treatment can damage the lining of the bowel. As the bowel heals, it makes new, small blood vessels. These are on the surface of the bowel lining, rather than deep within the bowel wall. Because these small blood vessels are on the bowel surface, they sometimes break and bleed. This can happen when you strain to pass stools (poo) or have hard stools.
Late effects are side effects that do not go away, or that start months or years after treatment. Most people who have bleeding from the back passage as a late effect of pelvic radiotherapy only notice bleeding occasionally. For a few people, bleeding can be heavy. They will need treatment.
Changes in the bowel lining often get better over time. But this can take 5 to 10 years. You may have an assessment with a specialist in the meantime.
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Tests
Bleeding can also be a sign of other problems such as haemorrhoids (piles) or straining on the toilet. Always tell your doctor or specialist nurse if you have any bleeding from the rectum, even if you think you know the cause. It is important to make sure there are not any serious problems.
Your doctor will examine your rectum. They may also refer you to have a sigmoidoscopy or colonoscopy. This is when a camera is used to look inside the bowel. A doctor or nurse passes a thin tube into the bowel. The tube is called a scope. It has a light and tiny camera on the end. It looks for any abnormal areas.
Treatment for bleeding from the bowel after pelvic radiotherapy
If the bleeding is mild and not affecting your daily life, you will probably not need treatment. Your specialist will give you advice about your bowel habits and how to avoid constipation.
This can help reduce bleeding.You are likely to need treatment if:
- bleeding is affecting your daily life
- you become anaemic – this means you have a low number of red blood cells.
Your doctor or specialist nurse will explain more about your treatment options and give you more information.
If you are taking anti-coagulants (blood-thinning drugs), your dose may be reduced and monitored.
The following treatments may reduce bleeding:
Sucralfate
A drug called sucralfate coats the lining of the bowel. This reduces inflammation and encourages healing. You have the drug as an enema. This means it is gently given as a liquid into the rectum, through a short tube. Your cancer team will show you how to do this yourself at home.
Thermal ablation
This treatment uses heat to seal areas that are bleeding. You have it during an endoscopy. This is when a doctor or nurse passes a thin, flexible tube with a light on the end into the rectum. Different types of thermal ablation include:
- radiofrequency ablation (RFA)
- argon plasma coagulation (APC).
Thermal ablation can cause complications, such as serious tissue damage. Your doctor will discuss this with you.
Formalin
This drug seals bleeding blood vessels. A doctor or nurse gives it to you during an endoscopy.
Formalin can cause complications, such as serious tissue damage. Your doctor will discuss this with you.
PuraStat®
This gel forms a coating over bleeding areas. A doctor or nurse gives it to you during an endoscopy. Your doctor can give you more information about this treatment.
Hyperbaric oxygen (HBO) therapy
This works by increasing the amount of oxygen that gets to tissue that has 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 is not widely available, so you may need to travel some distance for it.
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.
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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. Colorectal Disease. PubMed. 15 August 2022. Available at https://pubmed.ncbi.nl m.nih.gov/35969031/ [accessed 2026-03-04]
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 2026-03-04]
K Oakland, G Chadwick, J East, et al. Guidelines Diagnosis and management of acute lower gastrointestinal bleeding: guidelines from the British Society of Gastroenterology. Gut. British Medical Journal (BMJ). February 2019. Available at https://gut.bmj.com/content/gutjnl/68/5/776.full.pdf [accessed 2026-03-04]
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