OBJECTIVES: To describe the pathophysiology, incidence, and impact of radia- tion-induced diarrhea (RID), and to highlight the radiation oncology nurse’s role. DATA SOURCES: Primary and tertiary literature, and clinical experience. CONCLUSION: RID is a frequent complication of pelvic radiation, both when given alone and with chemotherapy. RID can significantly affect patient quality of life. Since diarrhea may be a difficult topic for patients to discuss, special care needs to be taken to avoid underdiagnosis of this problem. IMPLICATIONS FOR NURSING PRACTICE: The oncology nurse is uniquely situated to monitor patients for the development of RID, assess its severity and provide guidance to the health care team on the pa- tient’s status. OVERVIEW OF RADIATION- AND CHEMORADIATION- INDUCED DIARRHEA CLEMENT K. GWEDE MECHANISM AND INCIDENCE OF RADIATION-INDUCED DIARRHEA D IARRHEA occurring in patients treated with pel- vic or abdominal irradiation, either as single- modality therapy or in combination with chemo- therapy (combined modality therapy), is a common and well-documented side effect. 1-7 The onset of radiation-induced diarrhea (RID) typically occurs during the first 2 weeks after beginning radiation therapy (RT). Clinical manifestations of RID invariably include a high frequency of stools, with variable effects on stool consistency and volume. The mechanism of RID involves acute mechanical damage to the epithelial crypt cells of the gastrointestinal tract (Fig 1). 8,9 This damage results in cell death (necrosis), inflammation, and ulcer- ation of the intestinal mucosa, which is then exposed to irritating bile salts and becomes susceptible to opportunistic infections. Longer-term consequences of this damage include atrophy of the intestinal mucosal lining and fibrosis. Decreased absorption of water and electrolytes ensues. Diarrhea can also have an exudative component, with discharge of blood, mucus, and protein into the bowel (Fig 1). The incidence and severity of RID are both site- and dose- specific, varying with the total RT dose, the size of the RT field, the site being irradiated, and the dose per fraction. 8,9 With pelvic RT alone, studies show a very high incidence, with up to 70% of patients experiencing some form of diarrhea of any grade, and approximately 20% of patients experiencing grade 3 or 4 symptoms From the Department of Interdiscipli- nary Oncology, Moffitt Cancer Center and Research Institute, University of South Florida College of Medicine, Tampa, FL. Clement K. Gwede, PhD, MPH, RN: As- sistant Professor, Department of Interdis- ciplinary Oncology, Moffitt Cancer Center and Research Institute, University of South Florida College of Medicine, Tampa, FL. Address reprint requests to Clement K. Gwede, PhD, MPH, RN, Moffitt Cancer Center, 12902 Magnolia Dr, Mod 9-RT, Tampa, FL 33612. © 2003 Elsevier Inc. All rights reserved. 0749-2081/03/1904-0303$30.00/0 doi:10.1053/S0749-2081(03)00115-3 6 Seminars in Oncology Nursing, Vol 19, No 4, Suppl 3 (November), 2003: pp 6-10