Radiation enteritis is a functional disorder of the large and small bowel that occurs during or after a course of radiation therapy 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 1,000 cGy. Because curative doses for many abdominal or pelvic tumors range between 5,000 and 7,500 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]

Factors that influence the occurrence and severity of radiation enteritis include the following:

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., previous 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.

References

1. Perez CA, Brady LW, eds.: Principles and Practice of Radiation Oncology. 3rd ed. Philadelphia, Pa: Lippincott-Raven Publishers, 1998. 
   
   
2. O'Brien PH, Jenrette JM 3rd, Garvin AJ: Radiation enteritis. Am Surg 53 (9): 501-4, 1987.  [PUBMED Abstract]
   
   
3. Yeoh EK, Horowitz M: Radiation enteritis. Surg Gynecol Obstet 165 (4): 373-9, 1987.  [PUBMED Abstract]
   
   
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. Int J Radiat Oncol Biol Phys 12 (9): 1565-73, 1986.  [PUBMED Abstract]
   
   
5. Haddad GK, Grodsinsky C, Allen H: The spectrum of radiation enteritis. Surgical considerations. Dis Colon Rectum 26 (9): 590-4, 1983.  [PUBMED Abstract]
   
   

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