[MOL] RADIATION EFFECTS ON BOWELS.... [01967] Medicine On Line

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Radiation Enteritis

Supportive Care Information for Health Professionals

By The National Cancer Institute

Important: This information is intended for use by doctors and other health care professionals. If you are a cancer patient, your doctor can explain how it applies to you, or you can call the Cancer Information Service at 1-800-422-6237.


Radiation enteritis is a functional disorder of the large and small bowel that occurs during or following a course of radiotherapy to the abdomen, pelvis, or rectum.

The large and small bowel are very sensitive to ionizing radiation. Although the probability of tumor control increases with the radiation dose, so does the damage to normal tissues. Acute side effects to the intestines occur at approximately 1000 cGy. Since curative doses for many abdominal or pelvic tumors range between 5000 and 7500 cGy, enteritis is likely to occur.1

Almost all patients undergoing radiation to the abdomen, pelvis, or rectum will show signs of acute enteritis. Injuries clinically evident during the first course of radiation and up to 8 weeks later are considered acute.2 Chronic radiation enteritis may present months to years after the completion of therapy or it may begin as acute enteritis and persist after the cessation of treatment. Only 5% to 15% of persons treated with radiation to the abdomen will develop chronic problems.3

There are several factors that influence the occurrence and severity of radiation enteritis. These include:

1. Dose and fractionation.

2. Tumor size and extent.

3. Volume of normal bowel treated.

4. Concomitant chemotherapy.

5. Radiation intracavitary implants.

6. Individual patient variables (e.g., prior abdominal or pelvic surgery, hypertension, diabetes mellitus, pelvic inflammatory disease, inadequate nutrition).4,5

In general, the higher the daily and total dose delivered to the normal bowel and the greater the volume of normal bowel treated, the greater the risk of radiation enteritis. In addition, the individual patient variables listed above can decrease vascular flow to the bowel wall and impair bowel motility, increasing the chance of radiation injury.


1. Perez CA, Brady LW, Eds.: Principles and Practice of Radiation Oncology. Philadelphia: JB Lippincott, 1987.

2. O'Brien PH, Jenrette JM, Garvin AJ: Radiation enteritis. American Surgeon 53(9): 501-504, 1987.

3. Yeoh EK, Horowitz M: Radiation enteritis. Surgery, Gynecology and Obstetrics 165(4): 373-379, 1987.

4. Gallagher MJ, Brereton HD, Rostock RA, et al.: A prospective study of treatment techniques to minimize the volume of pelvic small bowel with reduction of acute and late effects associated with pelvic irradiation. International Journal of Radiation Oncology, Biology, Physics 12(9): 1565-1573, 1986.

5. Haddad GK, Grodsinsky C, Allen H: The spectrum of radiation enteritis. Surgical considerations. Diseases of the Colon and Rectum 26(9): 590-594, 1983.

Acute Radiation Enteritis

Diagnosis of Acute Enteritis

The cytotoxic effect of radiation therapy is mainly on rapidly proliferating epithelial cells, like those lining the large and small bowel. Crypt cell wall necrosis can be observed 12 to 24 hours after a daily dose of 150 to 300 cGy. Progressive loss of cells, villous atrophy, and cystic crypt dilation occur in the ensuing days and weeks. Patients suffering from acute enteritis may complain of nausea, vomiting, abdominal cramping, tenesmus, and watery diarrhea. With diarrhea, the digestive and absorptive functions of the gastrointestinal tract are altered or lost, resulting in malabsorption of fat, lactose, bile salts, and vitamin B12. Symptoms of proctitis, including mucoid rectal discharge, rectal pain, and rectal bleeding (if mucosal ulceration is present), may result from radiation damage to the anus or rectum.

Acute enteritis symptoms usually resolve within two to three weeks following the completion of treatment, and the mucosa may appear nearly normal.1

Assessment of Acute Enteritis

Patient examination and assessment of radiation enteritis should include the following: 2

1. The usual pattern of elimination.

2. The pattern of diarrhea, including:

A. Onset

B. Duration

C. Frequency, amount, and character of stools

D. Presence of other symptoms such as flatus, cramping, nausea,
abdominal distension, tenesmus, bleeding, and rectal excoriation

3. The nutritional status of the patient, including:

A. Height and weight

B. Usual eating habits, any change in eating habits, and amount of
residue in diet

C. Signs of dehydration such as poor skin turgor, serum electrolyte
imbalance, increased weakness, or fatigue

4. Present level of stress, coping patterns, and impact of signs and symptoms of enteritis on usual lifestyle patterns.

Medical Management of Acute Enteritis

Medical management includes treating diarrhea, dehydration, malabsorption, and abdominal or rectal discomfort. Symptoms usually resolve with medications, dietary changes, and rest. If symptoms become severe despite these measures, a treatment break may be warranted.

Medications might include:

1. Kaopectate, an antidiarrheal agent. Dose: 30-60 cc po after each loose bowel movement.

2. Lomotil (diphenoxylate hydrochloride with atropine sulfate). Usual dose: 1 to 2 tablets po every 4 hours as needed. Dose can be adjusted to the individual patient and his or her pattern of diarrhea. For example, one patient may achieve control of his or her diarrhea with 1 tablet tid, while another may require 2 tablets every 4 hours. Patients are not to exceed 8 tablets of Lomotil within a 24-hour period.

3. Paregoric, an antidiarrheal agent. Usual dose: 1 teaspoon po qid as needed for diarrhea. Paregoric may also be used alternating with Lomotil.

4. Cholestyramine, a bile salt sequestering agent. Dose: one package po after each meal and at bedtime.

5. Donnatal, an anticholinergic, antispasmodic agent used to alleviate bowel cramping. Dose: 1 to 2 tablets every 4 hours as needed.

6. Immodium (loperamide hydrochloride), a synthetic antidiarrheal agent. Recommended initial dose: 2 capsules (4 mg) po every 4 hours, followed by one capsule (2 mg) po after each unformed stool. Daily total dose should not exceed 16 capsules.

In addition to the above, relief from abdominal pain may be obtained by the use of narcotics. If proctitis is present, a steroid foam given rectally may offer relief of symptoms. Finally, if patients with pancreatic cancer are experiencing diarrhea during radiation therapy, they should be evaluated for the need for oral pancreatic enzyme replacement, as deficiencies in these enzymes alone can cause diarrhea.

The Role of Nutrition in Acute Enteritis

Damage to the intestinal villi from radiation therapy results in a reduction or loss of enzymes, one of the most important of these being lactase. Lactase is essential in the digestion of milk and milk products. Although there is no evidence that a lactose restricted diet will prevent radiation enteritis, a diet that is lactose free, low fat, and low residue can be an effective modality in symptom management.3

Recommended foods to avoid:

  • Milk and milk products. Exceptions are: buttermilk and yogurt, which are often tolerated since lactose is altered due to the presence of lactobacillus. Processed cheese may also be tolerated since the lactose is removed with the whey when it is separated from the cheese curd. Milkshake supplements, such as Ensure, are lactose free and may be used
  • Whole bran bread and cereal
  • Nuts, seeds, coconuts
  • 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 to encourage:

  • Fish, poultry, and meat that is cooked, broiled, or roasted
  • Bananas, apple sauce, peeled apples, 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:

  • Ingest food at room temperature2
  • Drink 3000 cc of fluid per day.
    Carbonated beverages should be allowed to lose their carbonation prior to drinking
  • Add nutmeg to food, which will help to decrease mobility of GI tract
  • Start a low residue diet on day 1 of radiation therapy treatment


1. Alimentary tract. In: Fajardo LF: Pathology of Radiation Injury. New York: Masson Publishers, 1982, pp 47-76.

2. Yasko JM: Care of the Client Receiving External Radiation Therapy. Reston VA: Reston Publishing Company, Inc., 1982.

3. Stryker JA, Bartholomew M: Failure of lactose-restricted diets to prevent radiation-induced diarrhea in patients undergoing whole pelvis irradiation. International Journal of Radiation Oncology, Biology, Physics 12(5): 789-792, 1986.

Chronic Radiation Enteritis

Diagnosis of Chronic Radiation Enteritis

Only 5% to 15% of the patients who receive abdominal or pelvic irradiation will develop chronic radiation enteritis. Signs and symptoms include colicky abdominal pain, bloody diarrhea, tenesmus, steatorrhea, weight loss, and nausea and vomiting. Less common are bowel obstruction, fistulas, bowel perforation, and massive rectal bleeding.1 The initial signs and symptoms occur within 6 to 18 months following radiotherapy. Radiologic findings include submucosal thickening, single or multiple stenoses, adhesions, and sinus or fistula formation.2 Microscopic findings include villi that are fibrotic, or may be lost altogether. Ulceration is common, varying from simple loss of epithelial layers to ulcers that may penetrate to different depths of the intestinal wall, even to the serosa. Lymphatic tissue is often atrophic or absent. The submucosa is severely diseased. Arterioles and small arteries show profound changes with hyalinization of the entire wall thickness. The muscularis is often distorted or focally replaced by fibrosis.

The diagnosis of chronic radiation enteritis may be difficult to make. Clinically and radiologically recurrent tumor needs to be ruled out. Due to the possible latency of the illness, it is essential that the physician obtain a detailed history concerning the patient's radiation therapy course. It is often advisable to include the radiation therapy physician in the continued management of the patient's care.

Treatment of Chronic Radiation Enteritis

Medical management of the patient's symptoms (which are similar to acute radiation enteritis) is indicated, with surgical management reserved for severe damage.3 Less than 2% of the 5% to 15% of patients who received abdominal or pelvic radiation will require surgical intervention.4

The timing and choice of surgical techniques remains somewhat controversial. A lower operative mortality (21% versus 10%) and incidence of anatomic dehiscence (36% versus 6%) have been reported with intestinal bypass than with resection.5,6 Those who favor resection point out that the removal of diseased bowel decreases the mortality rate for resection and is comparable to the bypass procedure.5 All agree that simple lysis of adhesions is inadequate and that fistulas require bypass.

Surgery should only be undertaken after careful assessment of the patient's clinical condition and extent of radiation damage because wound healing is often delayed, necessitating prolonged parenteral feeding after surgery. Even after apparently successful operations, symptoms may persist in a significant proportion of patients.7

Prevention of Chronic Radiation Enteritis

Treatment techniques that can minimize the risk of severe radiation enteritis include:

1. Radiation therapy techniques:

A. The use of a 3 or 4 field technique (as opposed to a 2 field
technique) to minimize the amount of small bowel exposed to

B. The treatment of the patient in a physical position that will aid in
removing as much small bowel from the treatment field as possible.
(For example, treating a patient with a full bladder each day to aid
in pushing the small bowel up and out of the pelvis when pelvic
radiation is given.)

C. Daily treatment of all fields a day resulting in a lower integral
dose and more homogenous dose distribution.

D. Use of computerized radiation dosimetry to best design the treatment
plan and the use of high energy treatment machines, such as linear
accelerators, that deliver a high dose to tumor volume while sparing
the normal structures.8

2. Surgery. Placing clips in high risk areas in order to better define the location or former location of the tumor to aid in radiation treatment planning.

3. Modification of treatment sequencing. An area for exploration is the sequencing of radiation, chemotherapy, and surgery and its influence on the severity of enteritis.

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