Radiation-associated colitis; Radiation proctitis
Radiation colitis results from exposure to ionizing radiation in the treatment of malignancies where the colon is localized in the path of the radiation beam. Tissues containing numerous actively dividing cells such as intestinal epithelial cells are more at risk for the development of radiation-induced injury. An acute and chronic type of radiation colitis is described. The acute changes develop very early within hours to several days after exposure. In this phase, the radiosensitive actively dividing cells of the intestinal epithelium are affected, and histologic changes are mainly observed in the mucosa. This acute syndrome, characterized by nausea, vomiting, and diarrhea, is usually transient and does not require further diagnostic or therapeutic action. Chronicradiation colitis develops after a symptom-free interval of 6 months to 30 years after radiation. The pathogenesis of this type of injury is based on...