Acute Radiation Injury
Radiation injury can be divided into an acute and a chronic phase. An acute injury occurs within six weeks of radiation treatment. Symptoms associated with an acute injury include diarrhea, urgency, fecal incontinence, and rectal bleeding. The onset of these symptoms can be attributed to the changes in the colon and rectum caused by radiation exposure. Symptoms may include acute inflammation, decreased mucus production, and accumulation of fluid beneath the intestinal lining (submucosal edema). Many patients will have resolution of these symptoms once the radiation exposure has ceased.
Treatment – If symptoms persist and are mild, antidiarrheals may be enough to manage them. Other treatments may be needed for those experiencing more severe symptoms. Several drug agents (e.g., sucralfate, misoprostol, steroids) have been studied in the treatment of acute radiation injury. These agents have had either limited success or have resulted in adverse outcomes.
Prevention – Two agents showing the greatest promise in preventing acute injury are amifostine and the 5 amino-salicylates (5 ASA). Amifostine is one protective agent, but its high cost will likely limit its use. In comparison, the 5-ASA agents are less expensive and have been shown to decrease symptoms associated with proctitis. Active delivery of the medication to the area of the rectum and last portion of the colon (rectosigmoid) is crucial as this is the location most often involved. Taking the agents orally is generally preferred to insertion of enemas or suppositories. Long-term follow-up studies are needed to assess whether the prevention of acute proctitis will decrease the risk of progression to chronic radiation injury.