Radiation enteritis

Section: Small bowel Curriculum: Curriculum, page 62

Definition

• Radiation therapy can cause an acute injury to the small and large intestines which develop during or shortly after treatment of a variety of malignancies.

Classification

• Acute
• Delayed

Risk factors

• Total dose, fraction size, treatment duration, volume of intestine within radiation field
• Radiosensitising chemotherapy
• Limited bowel motility
  • Adhesions
    • Previous abdominal surgery
    • Previous PID/peritonitis/endometriosis
  • Females, older patients, thin patients
  • Vascular disease
    • Smoking, diabetes, HTN, atherosclerosis
    • (Pretreatment condition is impacted by pathological changes of radiation enteritis)
  • Connective tissue disorders
    • E.g. RA, SLE

Pathogenesis/Pathophysiology

• Acute (within 3 months)
  • Crypt epithelium is rapidly proliferating
  • Radiation causes cells death - direct DNA damage and creation of oxygen free radicles
  • Initial damage occurs within hours
  • Crypt cell death - insufficient replacement of villous epithelium, mucosal barrier breakdown and mucosal inflammation
  • Leukocyte infiltration, crypt abscesses, ulceration
• Chronic (after 3 months)
  • ⇒ Mucosal atrophy, vascular sclerosis, progressive gut wall fibrosis
  • Mucosal atrophy
  • Intestinal wall fibrosis - submucosal, as ulcers heal
  • Microvascular sclerosis - endarteritis obliterans
  • Accelerated atherosclerosis

Clinical

• Acute

  • AP, N+V, diarrhoea, fatigue
  • Usually resolve within 1-3 months

• Chronic

  • Chronic, progressive disorder
  • Altered intestinal transit
  • Malabsorption
  • Bile salt - diarrhoea
  • Dysmotility
  • Strictures
  • Bacterial overgrowth
  • Bleeding ulcers
  • Abscess formation

• ⇒ Late changes of radiation of enteritis

  • Related to progressive intestinal wall vasculitis
  • Can lead to ulceration, stenosis, perforation or malnutrition

Investigation

• Deficiencies - B12 (SIBO), low albumin and anaemia from malnutrition/bleeding
• Stool cultures - R/O infection
• Imaging
  • CT - thickened bowel loops
• Differential diagnosis
  • Types of colitis
• Endoscopy
  • Palor with friability and telangiectasia.

Management

• Acute
  • Self limiting
  • Supportive cares
• Chronic
  • Predominantly conservative, medical with sx mx
  • Diet modification
  • Anti-diarrhoeals - Loperamide/Codeine
  • Sucralfate
  • Bile acid - sequestrants - Cholestyramine
    • Bile reabsorption in the TI may be impaired - bile acids in the colon precipitate diarrhoea. 
  • Hyperbaric oxygen therapy may be of benefit.
  • Abx - bacterial overgrowth (AP, bloating, diarrhoea)

Surgery

• Only when persistent complications
  • Persistent obstruction
  • Fistula
  • Perforation
  • Malignancy
  • GI bleeding that fails medical mx