Radiation Enteritis

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Basics

  • Radiation enteritis (RE) is an inflammatory injury to the large and small intestines resulting from radiation therapy (RT).
  • Many cancer patients receive RT as part of their treatment. As a result, the incidence of RE is now increasing (1).
  • Radiation toxicity to normal tissues is common and potentially devastating. Limiting radiation fields to prevent damage to normal tissue can be a barrier to curing malignancy (2)[A].
  • Radiation injury can also occur in settings of terrorist attacks (“dirty bombs”) and occupational accidents (3).

Description

  • Acute RE develops within hours to days of RT. It usually resolves within 2 to 6 weeks after the last treatment.
  • Chronic RE may occur as early as 2 months post-RT or as late as 30 years post-RT (1).
  • Chronic RE is usually progressive with potentially significant long-term morbidity and mortality.
    • Therapeutic options for chronic RE are limited.
    • Surgical resection has a role in selected cases.
  • Acute RE occurs in 60–80% of patients receiving intra-abdominal/pelvic RT.
  • Chronic RE occurs in 20% of patients receiving pelvic RT for gynecologic/urologic tumors (4).

Prevalence
  • There are 1.5 to 2 million patients with RE in the United States.
  • Incidence depends on radiation technique, treatment duration, type/stage of cancer, and other variables (5).

Etiology and Pathophysiology

  • Radiation injury activates intracellular mechanisms which alter cell division, leading to inflammation or cell death. Injury likely mediated indirectly by free-radical release, affecting DNA repair. Microvascular endothelial injury may also contribute (6).
  • Acute RE: multifactorial. The cytotoxic effects of RT suppress the Na+/K+ pump in rapidly dividing intestinal epithelial cells. A relative lactose intolerance ensues, and intestinal motility is affected. This causes mucosal atrophy and inflammation leading to fluid and nutrient loss and translocation of gut bacteria with subsequent bacterial overgrowth. The endothelium of the intestinal microvasculature is also impacted, altering local thrombogenesis (1).
  • Chronic RE: Progressive obliterative endarteritis (an occlusive vasculitis) causes tissue ischemia, leading to submucosal fibrosis and worsening ischemia (1).

Risk Factors

  • Patient factors (1,2)
    • Limited bowel mobility—due to physiology, adhesions, scarring
      • Women
      • Older age
      • Lower body mass index
      • Prior abdominal or pelvic surgery
      • Prior intra-abdominal infection
    • Vascular disease: DM, HTN, atherosclerosis, smoking
    • Collagen vascular disease: rheumatoid arthritis, systemic lupus erythematosus, polymyositis
    • Inflammatory bowel disease
  • Treatment factors (5,7)
    • Total RT dose
    • Treatment duration
    • Volume of intestine within RT field
    • Concurrent chemotherapy

General Prevention

  • Physical measures
    • “Belly board” device to reduce volume delivered to organs during abdominal and pelvic radiation
    • Surgical placement of intestinal sling
    • Bladder distension during RT
    • Trendelenburg position in pelvic RT
  • Treatment measures
    • Reduce field size.
    • Multiple field arrangements
    • Intensity-modulated RT
    • Brachytherapy
  • Broad-spectrum antibiotics may help in cases of confirmed bacterial overgrowth. Patients undergoing RT often become immunocompromised.
  • Cysteine, L-carnitine, amifostine, octreotide are being explored as preventive for both acute and chronic RE through antioxidant properties (1,5).

Commonly Associated Conditions

Radiation injury to other organs

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