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. 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.
Factors that influence the occurrence and severity of radiation enteritis include the following:
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.
Acute Radiation Enteritis
Radiation therapy exerts a cytotoxic effect 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 1.5 to 3 Gy. 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 (GI) 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 2 to 3 weeks after the completion of treatment, and the mucosa may appear nearly normal.
Patient examination and assessment of radiation enteritis includes the following:
- The usual pattern of elimination.
- The pattern of diarrhea, including the following:
- Frequency, amount, and character of stools.
- Presence of other symptoms such as flatus, cramping, nausea, abdominal distension, tenesmus, bleeding, and rectal excoriation.
- The nutritional status of the patient, including the following:
- Height and weight.
- Usual eating habits, any change in eating habits, and amount of residue in diet.
- Signs of dehydration such as poor skin turgor, serum electrolyte imbalance, increased weakness, or fatigue.
- Present level of stress, coping patterns, and impact of signs and symptoms of enteritis on usual lifestyle patterns.
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 may include the following:
- Kaopectate, an antidiarrheal agent. Dose: 30 cc to 60 cc by mouth after each loose bowel movement.
- Lomotil (diphenoxylate hydrochloride with atropine sulfate). Usual dose: One or two tablets by mouth every 4 hours as needed. Dose can be adjusted to individual patients and patterns of diarrhea. For example, one patient may achieve control of diarrhea with one tablet 3 times a day, while another patient may require two tablets every 4 hours. Patients are not to take more than eight tablets of Lomotil within a 24-hour period.
- Paregoric, an antidiarrheal agent. Usual dose: 1 teaspoon by mouth 4 times a day as needed for diarrhea. Paregoric may also be alternated with Lomotil.
- Cholestyramine, a bile salt sequestering agent. Dose: one package by mouth after each meal and at bedtime.
- Donnatal, an anticholinergic antispasmodic agent to alleviate bowel cramping. Dose: One or two tablets every 4 hours as needed.
- Imodium (loperamide hydrochloride), a synthetic antidiarrheal agent. Recommended initial dose: two capsules (4 mg) by mouth every 4 hours, followed by one capsule (2 mg) by mouth after each unformed stool. Daily total dose should not exceed 16 mg (eight capsules).
In addition to these medications, opioids may offer relief from abdominal pain. If proctitis is present, a steroid foam given rectally may offer relief from symptoms. Finally, if patients with pancreatic cancer are experiencing diarrhea during radiation therapy, they will be evaluated for oral pancreatic enzyme replacement, as deficiencies in these enzymes alone can cause diarrhea.
The role of nutrition
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.[Level of evidence: I]
Foods to avoid
- Milk and milk products. Exceptions are buttermilk and yogurt, which are often tolerated because lactose is altered by the presence of Lactobacillus. Processed cheese may also be tolerated because 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, and 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, 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.
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 the following:
- Colicky abdominal pain.
- Bloody diarrhea.
- Weight loss.
- Nausea and vomiting.
Less common are bowel obstruction, fistulas, bowel perforation, and massive rectal bleeding.
The initial signs and symptoms occur 6 to 18 months after radiation therapy. Radiologic findings include submucosal thickening, single or multiple stenoses, adhesions, and sinus or fistula formation. 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. Because of the possible latency of the illness, it is essential that the physician obtain a detailed history of 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.
Medical management of the patient's symptoms (which are similar to symptoms of acute radiation enteritis) is indicated, with surgical management reserved for severe damage.[Level of evidence: I] Fewer than 2% of the 5% to 15% of patients who received abdominal or pelvic radiation will require surgical intervention.
The timing and choice of surgical techniques remains somewhat controversial. A lower operative mortality (21% vs. 10%) and incidence of anatomic dehiscence (36% vs. 6%) have been reported with intestinal bypass as compared with resection.[Level of evidence: II] 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. All agree that simple lysis of adhesions is inadequate and that fistulas require bypass.
Surgery is undertaken only 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.
Treatment techniques that can minimize the risk of severe radiation enteritis include the following:
- Radiation therapy techniques, including the following:
- The use of a three- or four-field technique (as opposed to a two-field technique) to minimize the amount of small bowel exposed to treatment.
- The treatment of the patient in a physical position that will aid in removing as much small bowel from the treatment field as possible (e.g., 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).
- Daily treatment of all fields, resulting in a lower integral dose and more homogenous dose distribution.
- 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.
- Surgery. Placing clips in high-risk areas to better define the location or former location of the tumor and aid in radiation treatment planning.
- 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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