Bleeding from the bowel after pelvic radiotherapy

Bleeding from the back passage (rectum) after pelvic radiotherapy is common.

About bleeding from the bowel

Bleeding from the back passage (rectum) after radiotherapy is common. Most people who have it will only notice bleeding occasionally, and this often does not need treatment. But for a few people, bleeding can be heavy and cause concern.

Pelvic radiotherapy can damage the blood vessels in the wall 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 poo (stool), or has a slightly hard poo.

These changes in the bowel lining will often get better over time. But this can take 5 to 10 years. Bleeding may be a long-term problem after pelvic radiotherapy for some people.

Bleeding may not always be caused by the radiotherapy. It can be caused by piles (haemorrhoids) or straining on the toilet. Even if you think you know the cause, always tell your cancer doctor or specialist nurse if you have any bleeding from the back passage. Your doctor will do an examination of 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).

Treating bleeding from the bowel after pelvic radiotherapy

You will probably not need treatment if bleeding is due to radiotherapy changes, is mild, and not interfering with your daily life. You will be given advice about your bowel habits and how to avoid constipation. This will help reduce bleeding.

You are likely to need treatment if bleeding is interfering with your daily life, or if you become anaemic (have a low number of red blood cells). Your doctor or specialist nurse will explain more about your treatment options and give you more detailed information.

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


You may be offered treatment with a drug called sucralfate. If the blood is bright red, you have the drug as an enema. This is when a fluid (usually medicine) is gently passed into your back passage through a short tube. If the blood is darker and is coming from the colon, you take the drug as a tablet.

Sucralfate coats the lining of the bowel. This reduces inflammation and encourages healing. It is important to avoid getting constipated when you are being treated with sucralfate.

Thermal ablation

This treatment directs heat at areas that are bleeding. The heat seals the blood vessels and destroys damaged tissue. It is given during an endoscopy, where a doctor passes a thin, flexible tube with a light into your back passage. The most commonly used heat treatment is called 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.

Hyperbaric oxygen 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.


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.