Bleeding from the bowel after pelvic radiotherapy

Bleeding from the back passage (rectum) after pelvic radiotherapy is common. If bleeding is affecting your daily life, or if you become anaemic, you are likely to need treatment.

About bleeding from the bowel

Bleeding from the back passage (rectum) 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 a person strains to pass a bowel movement, or has slightly hard stools (poo).

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 and needs treatment. These changes in the bowel lining often get better over time. But this can take 5 to 10 years, so you may see a specialist for assessment in the meantime.


Bleeding can also be a sign of other problems such as piles (haemorrhoids) or straining on the toilet. Even if you think you know the cause, always tell your doctor or specialist nurse if you have any bleeding from the back passage. It is important to find out the cause and make sure there are not any serious problems.

Your doctor will examine your back passage. They may also refer you to have a camera test, to look at the inside of your rectum (a sigmoidoscopy or colonoscopy). This is where a doctor or nurse passes a scope (a thin tube with a light and tiny camera on the end) into the bowel to look for any abnormal areas.

Treating 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 will help reduce bleeding. We have more information about managing constipation.

If bleeding is affecting your daily life, or if you become anaemic (have a low number 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 information.

If you are taking blood-thinning drugs, your dose may be reduced and monitored.

Treatments that may reduce bleeding include the following:


A drug called sucralfate coats the lining of the bowel. This reduces inflammation and encourages healing. If the blood is bright red, you have the drug as an enema. This means the drug is gently given as a liquid into your back passage through a short tube. If the blood is darker, you take the drug by mouth as a tablet. It is important to avoid getting constipated when you are being treated with sucralfate.

Thermal ablation

This treatment uses heat to seal areas that are bleeding. It is given during an endoscopy, where a doctor or nurse passes a thin, flexible tube with a light on the end into your back passage. Different types of thermal ablation include radiofrequency ablation (RFA) and argon plasma coagulation (APC). There is a risk that thermal ablation can cause complications, such as serious tissue damage. Your doctor will discuss this with you.


This drug seals bleeding blood vessels. A doctor gives it to you during an endoscopy. There is a risk that formalin can cause complications, such as serious tissue damage. Your doctor will discuss this with you.


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.

We have more information about hyperbaric oxygen therapy.

About our information

  • References

    Below is a sample of the sources used in our pelvic radiotherapy information. If you would like more information about the sources we use, please contact us at

    Andreyev HJN, Muls AC, Norton C, et al. Guidance: The practical management of the gastrointestinal symptoms of pelvic radiation disease. Frontline Gastroenterology, 2015; 6, 53-72.

    Dilalla V, Chaput G, Williams T and Sultanem K. Radiotherapy side effects: integrating a survivorship clinical lens to better serve patients. Current Oncology, 2020; 27, 2, 107-112.

    The Royal College of Radiologists. Radiotherapy dose fractionation. Third edition. 2019. Available from: [accessed March 2021]. 

  • Reviewers

    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. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.