In contrast to acute radiation injury, chronic injury is an indolent process that can arise 3 months after therapy completion or up to 30 years later. In addition to the acute cellular toxicity, radiation causes a progressive, obliterative arteritis and submucosal fibrosis. Transmural injury of the bowel wall can lead to a progressive vasculitis, thrombosis, and, ultimately, varying degrees of ischemia and necrosis. This process may lead to narrowing of the bowel lumen and eventual obstruction. The effects of chronic radiation are primarily related to the total dose of radiation received as well as the total volume of tissue irradiated.19
There is some evidence to suggest that chronic
radiation proctitis is more likely to occur in those initially experiencing severe acute
This has been termed the consequential late effect.22,23
However, the absence of acute complications does not protect against the development of chronic radiation-induced injury. Several other factors have been identified that may increase the likelihood of developing chronic radiation injury. They include a history of prior abdominal or pelvic surgery,24
presumably secondary to adhesion formation resulting in entrapment of the bowel. In an attempt to limit the radiation dose delivered to normal bowel, Green investigated the utility of preradiation contrast radiography to determine the proximity of the bowel to the target organ.25
He found that patients who had prior abdominal or pelvic surgery were more likely to have bowel at risk and this bowel was unable to move from the radiation field. In addition to prior surgery, a history of vascular occlusive disease seems to be a predisposing factor for the development of radiation enteritis.26,27
Therefore, patients with underlying hypertension, diabetes, and cardiovascular disease may be especially at risk for the development of symptomatic radiation enteritis.
Late intestinal injury may arise with a variety of signs and symptoms ranging from chronic abdominal pain, constipation, obstruction, or mild GI blood loss to the sudden onset of abdominal pain and toxemia consistent with an acute abdomen. Any patient with a history of radiation to the abdomen or pelvis presenting with GI complaints should raise suspicion for radiation-related toxicity until proved otherwise. One must keep in mind that patients with chronic radiation changes often develop dense intra-abdominal adhesions after radiation exposure and have very little free domain in their abdomen. Localized perforations may occur, and an elevated awareness is required to avoid missing a life-threatening diagnosis. On the other hand, exploratory surgery for chronic radiation injury should be approached with caution, as surgery carries significant morbidity and mortality in this population of patients.28,29
In the nonemergent, radiated surgical patient, preoperative imaging is an important component that can be critical in assisting the surgeon in planning the operation.30,31,32
Radiographic assessment of chronic radiation enteritis or colitis has most commonly utilized barium enema or CT. A spectrum of findings has been demonstrated on barium enema, ranging from normal findings (seen in 15%) to ulceration and contour abnormalities, intestinal fixation, decreased distensibility, and stenoses.33
The “omega sign,” caused by bilateral retraction at the base of a narrowed sigmoid loop, was seen in nearly 60% of patients with radiation colitis. Endoscopy was found to be complementary to barium study as it allowed better assessment of mucosal abnormalities and ulceration.33
Surprisingly, CT was not found particularly useful in diagnosing radiation enteritis.30,31
The findings required correlation with the clinical history and were generally nonspecific, including bowel wall thickening and stenosis.