National Cancer Institute
Last Modified: August 23, 2004
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.
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.
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.
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.
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.
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