Radiation Enteritis

Overview

Radiation enteritis is a complication of radiotherapy, most often affecting the ileum and rectum following pelvic irradiation. It results from direct radiation-induced injury to the intestinal mucosa, muscularis, and vasculature. While acute symptoms usually resolve within weeks, chronic forms may cause long-standing bowel dysfunction, obstruction, or even resemble chronic irritable bowel syndrome. Recognition and appropriate management are key in oncology follow-up care.

Definition

Radiation enteritis is inflammation and structural damage of the bowel due to ionising radiation exposure, most commonly as a side effect of therapeutic pelvic radiotherapy.

Aetiology

• Radiotherapy exposure, typically pelvic or abdominal
• Commonly affected:
  • Ileum
  • Rectum
• Threshold dose: >40 Gray

Morphology / Pathophysiology

• Radiation leads to progressive intestinal damage:
  • Muscle fibre atrophy
  • Mucosal ulceration
  • Ischaemia → fibrosis and stricture formation
• These changes impair motility and absorption and predispose to obstruction

Clinical Features

Acute Radiation Enteritis (within 6 weeks of exposure):

• Nausea
• Vomiting
• Diarrhoea
• Abdominal pain

Chronic Radiation Enteritis (>3 months after exposure):

• Intermittent abdominal pain (often due to partial obstruction)
• Malabsorption
• Bowel frequency and tenesmus
• Symptoms may mimic chronic irritable bowel syndrome

Investigations

Although not detailed in the original source, the following may be useful:

• Endoscopy or capsule endoscopy
• CT scan to assess strictures or perforation
• Biopsies to exclude malignancy in chronic symptoms

Management

• Supportive management for mild or self-limiting cases
• Surgical intervention is reserved for complications such as:
  • Bowel obstruction
  • Bowel perforation

Complications

• Fibrotic strictures → partial or complete obstruction
• Ulceration → bleeding
• May resemble or lead to chronic irritable bowel syndrome

Differential Diagnosis

• Crohn’s disease
• Ulcerative colitis
• Ischaemic colitis
• Infectious colitis
• Colorectal cancer

Summary

Radiation enteritis is a gastrointestinal complication resulting from therapeutic radiation exposure, particularly affecting the ileum and rectum. It may present acutely or chronically and can lead to significant complications such as strictures, bowel obstruction, and symptoms mimicking irritable bowel syndrome. For a broader context, see our Gastrointestinal Overview page.