What Is Radiation Enteritis

  • James Thomas Bachelor of Science - BSc, Biology, University of Leeds, UK
  • Stephanie Leadbitter MSc Cancer Biology & Radiotherapy Physics, BSc (Hons) Biomedical Science, University of Manchester, UK

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Radiotherapy is widely used in the treatment of almost every type of cancer, but this kind of therapy carries with it a significant risk of unwanted side effects. If you’re receiving radiation treatment for cancer of the pelvis or abdomen, it’s important to be aware of one such side effect experienced by many patients of this cancer: radiation enteritis.

Radiation enteritis is a medical complication of radiotherapy, commonly found in patients undergoing treatment for cancers located in the pelvis and abdomen. Symptoms often present as diarrhoea and abdominal pain, though more serious medical conditions can arise in cases of chronic illness. Radiation enteritis often isn’t entirely curable and can be very difficult to avoid if you’re having radiation treatment, but your doctor will be able to give you advice on how to limit your risk as much as possible and ease any uncomfortable symptoms you might be having.

In this article, we’ll explore the cause of radiation enteritis, as well as the symptoms associated with the condition, and bring to your attention some of the techniques available to help prevent and treat serious medical complications.


Radiation therapy (also known as radiotherapy) is a type of cancer treatment that uses high-energy radiation to kill cancerous cells and tumours. Used appropriately, radiotherapy can be very effective in helping to cure cancer, but unavoidable damage to nearby healthy cells can cause unpleasant side effects.1

Radiation enteritis is a medical complication caused by inflammation of the small and/or large intestine following radiation treatment. It’s common in patients receiving radiotherapy for tumours in the pelvic and abdomen areas, with long-term effects estimated to occur in around 90% of patients undergoing pelvic radiotherapy. 

The condition can be acute or chronic, depending on when symptoms arise. Acute radiation enteritis develops during your course of radiotherapy and tends to last only a short while after the treatment has finished. Chronic radiation enteritis, however, can occur many years down the line and can lead to further complications requiring more specific treatment.


Ionising radiation used in radiotherapy travels with enough energy to remove electrons from the molecules that make up cells in the body, leading to cell death2. In the cancerous cells of tumours, ionising radiation damages the DNA and so prevents the cell from rapidly dividing (proliferating) - a key characteristic of cancer.3 

Exposing healthy tissue to radiation also damages DNA and causes cell death4. Radiation enteritis arises from repeated damage to the intestinal mucosa caused by prolonged exposure to ionising radiation5. The cells that comprise the lining of the intestines are particularly sensitive to radiation due to the mechanism by which these cells repair, making enteritis even more likely in patients undergoing radiotherapy.

Risk factors

Radiation enteritis is somewhat unavoidable as a side-effect of radiotherapy, but there are a number of factors which might bring about an increased risk.

The most prominent risk factors include:6

  • Dosage and duration of radiation
  • Chemotherapy
  • Previous abdominal surgery
  • Diabetes


Most sufferers of acute radiation enteritis predominantly experience diarrhoea and abdominal pain, though symptoms might also include:6

  • Stomach bloating
  • Nausea
  • Vomiting
  • Rectal bleeding

Depending on your course of radiotherapy and which type of radiation enteritis you have, symptoms can last for varying lengths of time. In cases of acute radiation enteritis, symptoms often resolve without medical intervention, lasting for less than 12 weeks after the conclusion of radiation treatment. Symptoms in chronic cases can, however, last much longer, often persisting for up to several months. 


In people with chronic enteritis, typical symptoms might further develop into more serious medical complications, such as:5

  • Intestinal fistula - Excessive damage to the lining of the intestine can cause perforation, leading to the formation of an opening which connects the intestine to another internal organ of the body, such as the stomach. Intestinal fistulas often take a long time to manifest, and treating them can be very challenging, often requiring surgery to remove the affected area.
  • Intestinal stricture - When the tissues of the intestine are injured, inflammation and damage can lead to the thickening of the digestive tract and the formation of thick scars as tissues heal. This ultimately leads to narrowing in a region of the intestine, which can develop into an intestinal blockage and further serious complications, not least of which is an increased risk of infection.
  • Malabsorption - In some cases, damage to the intestine can hinder its ability to absorb nutrients from the food that you eat, leaving nutrients to pass out of your body in the stool. Often, people experience diarrhoea as a side-effect, which only exacerbates the problem as food moves too rapidly through the digestive system. Over long periods of time, your body will start to show signs of malnutrition, potentially leading to a range of serious health complications, including immune system deficiency and impaired growth and development.


In order for your doctor to diagnose radiation enteritis, they will likely start by asking you about your symptoms and medical history, including any previous experience you may have with radiation. 

Should they feel it necessary, your doctor might also order for some tests that will help them to assess the condition of your intestine, usually including:

  • Colonoscopy - Your doctor may use a thin, flexible tube with a camera at one end (colonoscope) inserted into the rectum to view and assess the condition of your colon (large intestine) and the lower part of your small intestine.
  • Endoscopy - Similar to colonoscopy, a long and flexible tube with a camera at one end is inserted into the mouth, allowing your doctor to view the upper portion of your small intestine.
  • Imaging Tests - X-rays, CT scans and MRI scans can help doctors to form a picture of your intestines, allowing them to assess the condition of the tissues implicated in radiation enteritis.


In most cases of acute radiation enteritis, symptoms typically resolve on their own within a few months. If, however, you're struggling to manage uncomfortable symptoms, there are some things you can do that might offer some relief. 

Certain medications can help to alleviate painful symptoms, though it’s important to note that these alone will not necessarily cure your symptoms. Your doctor will likely recommend that you take antidiarrhoeal medication to help slow down intestinal activity while you recover, helping you to better regulate bowel movements. Corticosteroids and over-the-counter pain relievers can also be useful in helping to reduce discomfort from inflammation, though you should always discuss how these might influence your symptoms with your healthcare provider.

To help manage difficult symptoms in the short term, it is often recommended that you make sure to drink plenty of water, as water helps to break down food for your digestive system to absorb nutrients. Many people also find that one of the best ways of improving symptoms is by following a diet designed to reduce irritation of the digestive system. Typically, this involves limiting your intake of dairy products and fatty or high-fibre foods, which naturally speed up bowel movements.

In cases of chronic enteritis, patients who develop serious complications like intestinal fistulas and strictures will often require surgery.7 Surgeons aim to bypass the portion of the intestine that is damaged by removing it from the digestive tract, but this procedure comes with a certain degree of risk. Some medical experts are reluctant to suggest surgery as a treatment option unless absolutely necessary due to the potential for further complications like short bowel syndrome.

Preventing radiation enteritis

Although there is a high likelihood of intestinal damage during radiotherapy that leads to radiation enteritis, steps can be taken to limit the degree of harm and, hence, the severity of enteritis. These include: 

  • Taking antioxidants during radiotherapy has been shown to reduce side effects by protecting cells from damage caused by free radicals.8
  • New techniques of radiotherapy, which enable more accurate delivery of radiation to the exact tissues being targeted. Your care team might also decide to reduce your dose of radiation if enteritis starts to be suspected.


Radiation enteritis is a common complication of radiotherapy to the pelvis and abdomen. It occurs when radiation damages healthy tissues in the lining of the intestines, leading to inflammation and pain.

Patients with acute enteritis usually experience symptoms involving diarrhoea, abdominal pain and nausea. These symptoms tend to last for several weeks following radiation treatment and can be managed with medication and dietary changes.

Chronic enteritis often lasts much longer and has the potential to cause serious complications that require more specific treatment. 

It might not be possible to entirely avoid radiation enteritis, but some techniques can help to reduce the risk of serious complications. Your medical care team will be able to advise you on how best to avoid excessive radiation exposure and to treat any difficult symptoms you might encounter.


  1. Cancer Research UK. What Is Radiotherapy? [Internet]. 2023. [cited 27 Oct. 2023]. Available from: https://www.cancerresearchuk.org/about-cancer/treatment/radiotherapy/what-is-radiotherapy.
  2. CDC. ‘Ionizing Radiation’. Centers for Disease Control and Prevention, 29 June 2021  [cited 27 Oct. 2023]. Available from:, https://www.cdc.gov/nceh/radiation/ionizing_radiation.html.
  3. National Cancer Institute. What Is Cancer? 2007.[cited 27 Oct. 2023] Available from: https://www.cancer.gov/about-cancer/understanding/what-is-cancer.
  4. Lobo, V., et al. ‘Free Radicals, Antioxidants and Functional Foods: Impact on Human Health’. Pharmacognosy Reviews, 2010, vol. 4;, no. 8, 2010, pp. 118–26. Available from:PubMed Central, https://doi.org/10.4103/0973-7847.70902.
  5. Bhutta, Beenish S., et al. ‘Radiation Enteritis’. StatPearls, StatPearls Publishing, 2023. Available from: http://www.ncbi.nlm.nih.gov/books/NBK526032/.
  6. Vancamelbeke, Maaike, and Séverine Vermeire. ‘The Intestinal Barrier: A Fundamental Role in Health and Disease’. Expert Review of Gastroenterology & Hepatology, 2017, 11,9,, pp. 821–34. Available from:  https://doi.org/10.1080/17474124.2017.1343143.
  7. Shadad, Abobakr K., et al. ‘Gastrointestinal Radiation Injury: Symptoms, Risk Factors and Mechanisms’. World Journal of Gastroenterology : WJG, vol. 19, no. 2, Jan. 2013, p. 185. Available from:  https://doi.org/10.3748/wjg.v19.i2.185.
  8. Huang, Yuhua, et al. ‘Surgery for Chronic Radiation Enteritis: Outcome and Risk Factors’. Journal of Surgical Research, vol. 204, no. 2, Aug. 2016, pp. 335–43. Available from:  https://doi.org/10.1016/j.jss.2016.05.014.
  9. Anwar, Mumtaz, et al. ‘Antioxidant Supplementation: A Linchpin in Radiation-Induced Enteritis’. Technology in Cancer Research & Treatment, vol. 16, no. 6, Dec. 2017, pp. 676–91. Available from: https://doi.org/10.1177/1533034617707598.

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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James Thomas

Bachelor of Science - BSc, Biology, University of Leeds

James is a Genetic Scientist with several years experience in the (cancer) pharmaceutical clinical trial industry. He has varied experience in healthcare, supplementing an educational background in Human Biology with professional roles in the care sector, in hospitals, and in the clinical laboratory.

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