Radiation enteritis is a condition that arises as a side effect of radiotherapy during the treatment of cancer. It may cause gastrointestinal symptoms such as a change in bowel habits and abdominal pain, which may be acute or chronic.
Radiation enteritis (RE) is an iatrogenic ailment that involves injury to the small intestine, resulting from radiation therapy employed in the treatment of malignancies. RE affects the majority of patients undergoing radiation in the abdomen or pelvis . Factors that predispose patients to RE entail high dose radiotherapy, cardiovascular disease, and those simultaneously receiving chemotherapy.
RE may be acute or chronic in nature. Acute disease may present with abdominal pain, in addition to a variety of nonspecific gastrointestinal (GI) symptoms such as nausea, vomiting, anorexia, and change in bowel habits. These occur and peak with 2 to 5 weeks of initiation of therapy . Acute RE often resolves spontaneously, after 3 months of treatment .
Chronic RE has a much slower onset and may transpire years after exposure to radiotherapy . It occurs due to repeated injury of the gut, leading to inflammation and atrophy of mucosal cells, fibrosis, and impaired healing . The nature and severity of symptoms correspond with the associated damage . Furthermore, radiotherapy affects local blood vessels, causing arterial occlusion by surrounding tissues, that is, endarteritis obliterans, leading to chronic ischemia. Chronic RE manifests as nonspecific GI symptoms, bowel obstruction, fat malabsorption and abdominal pain associated with food intake . Micronutrient deficiencies, such as vitamin B12 and calcium, are also known findings.
RE is a significant problem, as it negatively impacts the quality of life. Furthermore, the condition may not receive adequate attention and treatment due to patients being less forthcoming about GI complaints, as well as clinicians failing to recognize and refer the former to specialists  . It is thus important to educate patients about the possible gastrointestinal side effects of radiotherapy and encourage a preventative health-seeking behavior. In radiation enteritis, the medical history is of significant importance, as it may reveal radiotherapy exposure, possibly many years prior to presentation. Clinical examination further aids in diagnosis.
Biochemically, chronic RE may be evidenced by anemia and malnutrition . Sepsis and raised inflammatory markers may be observed if there is an intestinal obstruction. There may also be a concurrent electrolyte imbalance, abnormal liver function tests, and coagulopathy.
Radiological techniques are useful, as there are a number of changes that are detectable. Computed tomography (CT) and magnetic resonance imaging (MRI) scans may show signs of intestinal wall inflammation such as thickening of the bowel walls, edema, and features of intestinal obstruction. Fistula formation, between the bowel and adjacent pelvic structures, may also be visualized in this way. The small bowel, as inspected via fluoroscopic enteroclysis, may exhibit signs of edema and fibrosis, stenosis and ulcers. There may be segments that appear similar to a stack of coins. Other radiological exams carried out include barium studies. Invasive techniques include endoscopy.