Radiation proctitis can occur at two times after treatment:
Acute radiation proctitis — symptoms occur in the first few weeks after therapy. These symptoms include diarrhea and the urgent need to defecate, often with inability to do so (tenesmus). Acute radiation proctitis usually resolves without treatment after several months, but symptoms may improve with butyrateenemas. This acute phase is due to direct damage of the lining (epithelium) of the colon.
Chronic radiation proctitis — symptoms may begin as early as several months after therapy but occasionally not until several years later. These symptoms include diarrhea, rectal bleeding, painful defecation, and intestinal blockage. Intestinal blockage is a result of narrowing of the rectum which blocks the flow of feces. Connections fistulae may also develop between the colon and other parts of the body such as the skin or urinary system. Chronic radiation proctitis occurs in part because of damage to the blood vessels which supply the colon. The colon is therefore deprived of oxygen and necessary nutrients. Symptoms such as diarrhea and painful defectation may be treated with oral opioids and stool softeners, respectively. Complications such as obstruction and fistulae may require surgery. Several other methods are under development as of 2005 to lessen the effects of radiation proctitis. These include sucralfate, hyperbaric oxygen therapy, corticosteroids, metronidazole, and argon plasma coagulation.
Babb RR. Radiation proctitis: a review. Am J Gastroenterol. 1996 Jul;91(7):1309-11. Review. PMID 8677984