National Cancer Institute

Posted Date: Aug 23, 2004



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This patient summary on radiation enteritis (inflammation of the intestine) is adapted from a summary written for health professionals by cancer experts. This and other credible information about cancer treatment, screening, prevention, supportive care, and ongoing clinical trials is available from the National Cancer Institute. Radiation therapy often leads to radiation enteritis, which is a disorder of the large and small bowel. This brief summary describes radiation enteritis and its causes, symptoms, and treatment.


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Radiation enteritis is a malfunction of the large and small bowel that occurs during or after radiation therapy to the abdomen, pelvis, or rectum.

The large and small bowel are very sensitive to radiation. The amount of damage to normal tissues increases as the radiation dose increases; because larger doses are needed for most tumors in the abdomen and pelvis, enteritis is likely to occur.

Almost all patients undergoing radiation to the abdomen, pelvis, or rectum will show signs of acute enteritis. Acute symptoms are those that appear during the first course of radiation therapy and up to 8 weeks later. Chronic radiation enteritis may appear months to years after radiation therapy is completed, or it may begin as acute enteritis and continue after treatment stops. Only 5% to 15% of persons treated with radiation to the abdomen will develop chronic problems.

Several factors determine the occurrence and severity of radiation enteritis. These factors include the dose of radiation, tumor size and spread, amount of normal bowel treated, concurrent chemotherapy, use of radiation implants, and individual patient factors (such as previous surgery to the abdomen or pelvis, high blood pressure, diabetes, pelvic inflammatory disease, or poor nutrition).

The risk of radiation enteritis usually increases as the dose of radiation and the percentage of normal bowel treated increase. Also, the patient factors listed above can decrease blood flow to the bowel wall and affect bowel movement, increasing the chance of radiation injury.

Acute Radiation Enteritis

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Radiation therapy mainly affects rapidly dividing cells such as the cells lining the large and small bowel. An increasing number of cells die, leading to other problems over the next few days and weeks. Patients with acute enteritis may complain of nausea, vomiting, abdominal cramping, the frequent urge to have a bowel movement, and watery diarrhea. With diarrhea, the gastrointestinal tract does not function as efficiently, and fat, lactose, bile salts, and vitamin B12 are not well absorbed. Symptoms of an inflamed rectumincluding a mucus-like discharge, rectal pain, and rectal bleedingmay result from radiation damage to the anus or rectum.

Symptoms of acute enteritis usually get better 2 to 3 weeks after treatment ends.


Patients should be examined and asked questions about the following:

  • Usual pattern of bowel movements.
  • Pattern of diarrhea, including when it started; how long it has lasted; frequency, amount, and type of stools; and other symptoms (such as gas, cramping, bloating, urgency, bleeding, and rectal soreness).
  • Nutrition of the patient, including height and weight, usual eating habits, any change in eating habits, amount of fiber in the diet, and signs of dehydration (such as poor skin tone, increased weakness, or fatigue).
  • Current level of stress, coping ability, and changes in lifestyle caused by the enteritis.


Treatment of acute enteritis includes treating the diarrhea, loss of fluids, poor absorption, and stomach or rectal pain. These symptoms usually get better with medications, changes in diet, and rest. If symptoms become worse even with this treatment, then cancer treatment may have to be stopped, at least temporarily.

Medication may be prescribed, including antidiarrheals to stop diarrhea, opioids to relieve pain, and steroid foams to relieve rectal inflammation and irritation. If patients with pancreatic cancer have diarrhea during radiation therapy, they may need pancreatic enzyme replacement, because not having enough of these enzymes can cause diarrhea.


Nutrition also plays a role in acute enteritis. When intestines are damaged by radiation therapy, production of enzymes, especially lactase, decreases or stops entirely. Lactase is essential in the digestion of milk and milk products. A lactose-free, low-fat, and low-fiber diet may help to control symptoms of acute enteritis.

    Recommended foods to avoid:

  • Milk and milk products (except buttermilk and yogurt). Processed cheese may be tolerated because the lactose is removed in processing. Lactose-free milkshake supplements such as Ensure may also be used.
  • Whole-bran bread and cereal.
  • Nuts, seeds, and coconut.
  • Fried, greasy, or fatty foods.
  • Fresh and dried fruit and some fruit juices (such as prune juice).
  • Raw vegetables.
  • Rich pastries.
  • Popcorn, potato chips, and pretzels.
  • Strong spices and herbs.
  • Chocolate, coffee, tea, and soft drinks with caffeine.
  • Alcohol and tobacco.

    Foods that are recommended:

  • Fish, poultry, and meat that is cooked, broiled, or roasted.
  • Bananas, applesauce, peeled apples, and apple and grape juices.
  • White bread and toast.
  • Macaroni and noodles.
  • Baked, boiled, or mashed potatoes.
  • Cooked vegetables that are mild, such as asparagus tips, green and waxed beans, carrots, spinach, and squash.
  • Mild processed cheese, eggs, smooth peanut butter, buttermilk, and yogurt.

    Helpful hints:

  • Eat food at room temperature.
  • Drink 3 liters of fluid a day. Carbonated beverages should be allowed to lose their carbonation before being consumed.
  • Add nutmeg to food to help decrease movement of the gastrointestinal tract.
  • Start a low-fiber diet on the first day of radiation therapy.

Chronic Radiation Enteritis

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Only 5% to 15% of the patients who receive radiation therapy to the abdomen or pelvis will develop chronic radiation enteritis. Symptoms include wave-like abdominal pain, bloody diarrhea, frequent urges to have a bowel movement, greasy and fatty stools, weight loss, and nausea and vomiting. Less common are bowel obstruction, holes in the bowel, and heavy rectal bleeding. Symptoms usually appear 6 to 18 months after radiation therapy.

Before determining that chronic radiation enteritis is causing these symptoms, recurrent tumors need to be ruled out. The radiation history of the patient is important in making the correct diagnosis.


Symptoms of chronic radiation enteritis are treated in the same way as symptoms of acute radiation enteritis. Surgery is used to treat severe damage. Fewer than 2% of affected patients will require surgery to control their symptoms.

Two types of surgery may be used: intestinal bypass or complete removal of the diseased intestines. The patient's condition should be considered before surgery is attempted, however, because wound healing is often slow and may require long-term tube feeding. Even after surgery, many patients may still have symptoms.

To minimize the risk of chronic radiation enteritis, health professionals use different methods to try and reduce the area that is exposed to radiation. Patients may be positioned to protect as much of the small bowel as possible from the radiation treatment, or may be asked to have a full bladder during treatment to help push the small bowel out of the way. The amount of radiation may be adjusted to deliver lower amounts more evenly or higher amounts to specific areas. If a patient has surgery, clips may be placed at the tumor site to help designate the area to be irradiated.

Changes to This Summary (08/23/2004)

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The PDQ® cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

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