Radiation Enteritis — Bowel Inflammation After Radiotherapy

Radiation enteritis refers to injury sustained by the intestinal mucosa when therapeutic ionising radiation damages rapidly dividing epithelial cells lining the bowel. This disruption triggers a local inflammatory cascade, mucosal sloughing, and impaired barrier function. In the acute phase, tissue oedema and loss of surface area hinder normal water and electrolyte absorption.

Chronic radiation enteritis involves progressive microvascular injury, obliterative endarteritis, and transmural intestinal fibrosis. Over time, tissues receive reduced blood supply, which may cause bowel wall thickening, strictures, ulcerations, or abnormal passages known as fistulae. While modern radiotherapy planning limits radiation fields to spare healthy surrounding structures, intestinal tissues remain inherently sensitive to radiation exposure.

Recognising radiation enteritis early allows clinical teams to alleviate distressing bowel symptoms before severe dehydration, weight loss, or malnutrition take hold. Unmanaged diarrhoea can disrupt scheduled radiotherapy sessions, potentially compromising the overall effectiveness of cancer treatment. Furthermore, understanding that gut issues can emerge years after treatment helps patients seek prompt evaluation for chronic complications, preventing delays in addressing bowel strictures or nutrient malabsorption.

There is no single biomarker for radiation enteritis. Diagnosis typically involves blood tests assessing full blood counts, electrolytes, and inflammatory markers, alongside stool tests to exclude bacterial infections like Clostridioides difficile. In chronic scenarios, endoscopic evaluations, such as colonoscopy or flexible sigmoidoscopy, assess mucosal appearance. Cross-sectional imaging via CT enterography or MRI enterography evaluates bowel wall thickness, strictures, and obstruction.

Radiation enteritis occurs predominantly in individuals receiving pelvic or abdominal radiotherapy. It is most frequently encountered during or after treatment for colorectal cancer, gynaecological malignancies such as cervical, uterine, and ovarian cancers, and prostate or bladder cancer. It may also affect people receiving radiotherapy for retroperitoneal sarcomas, testicular tumours involving retroperitoneal lymph nodes, or lymphoma affecting the abdominal region.

Management focuses on symptom control and maintaining hydration. Acute symptoms often respond to dietary adjustments, including low-residue or low-fibre meals, and antimotility medicines like loperamide. In chronic cases, treatment may involve bile acid sequestrants, nutritional supplementation for malabsorption, or endoscopic dilation of strictures. In rare cases involving intestinal perforation, fistulae, or complete mechanical obstruction, surgical intervention may be required.