Noninfectious colitis
Radiation enterocolitis

Topic Completed: 1 October 2014

Minor changes: 6 April 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Radiation enterocolitis[TIAB]

Elliot Weisenberg, M.D.
Page views in 2020: 4,399
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Cite this page: Weisenberg E. Radiation enterocolitis. website. Accessed April 19th, 2021.
Definition / general
  • Radiation induced injury to anorectum
  • Acute or chronic
  • Over 100,000 American patients annually receive therapeutic pelvic radiation for malignancies of prostate, anus, rectum, uterine cervix, endometrium, urinary bladder and rarely other sites
  • Acute radiation proctitis occurs in nearly all patients but is generally self limited and not biopsied
  • Only 5 to 15% develop chronic radiation proctitis, although with improving techniques for radiation therapy the incidence is decreasing
  • Ionizing radiation primarily damages DNA but may affect cell membranes and proteins
  • The injury in acute radiation proctitis occurs hours to days after radiation therapy and is primarily mucosal, mostly affecting epithelial cells with high turnover
  • Injury causes apoptosis of epithelial cells, decreased mitotic activity, fibrinoid necrosis of small vessels, ulceration and possibly eosinophilia or crypt abscesses
  • Injury generally resolves within two months
  • In chronic radiation proctitis, mesenchymal tissue is directly most damaged
  • Chronic radiation proctitis manifests months to years or even decades after radiation therapy
  • Endothelial damage causes arterial sclerosis with obliterative endarteritis of small vessels, leading to chronic ischemia and associated fibrosis
  • These changes can lead to ulcers, bleeding, stenosis, strictures, fistulas, bleeding
Clinical features
  • Acute radiation proctitis: may be subclinical but most patients suffer variably from diarrhea, pain, tenesmus, hematochezia
  • Chronic radiation proctitis: may be associated with diarrhea, ulcers, pain, bleeding, stenosis, strictures, fistulas
    • Many patients suffer progressive disease that may be lifelong
  • Radiation proctitis risk is higher in patients with higher radiation doses, less fractionation of the dose, thinner patients, the elderly, concurrent or subsequent chemotherapy, collagen vascular disease, hypertension, diabetes mellitus
  • Acute radiation proctitis: clinical disease that is rarely biopsied
  • Chronic radiation proctitis: usually biopsied; a detailed history is essential to proper interpretation of the biopsy
Case reports
  • Acute radiation proctitis is managed conservatively
  • Chronic radiation proctitis: may be managed conservatively with laser therapy; topical treatments include formalin or radiofrequency ablation but many patients require surgical intervention
Clinical images

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Edematous rectal mucosa

Rectal mucosa

Gross description
  • Endoscopic evaluation of acute radiation proctitis shows edematous, dusky red rectal mucosa
  • Endoscopy of chronic radiation proctitis shows mucosal atrophy, ectatic superficial capillaries and variable stenosis, strictures and fistulas
Microscopic (histologic) description
  • Acute disease demonstrates epithelial flattening, erosions, increased apoptotic bodies, decreased mitotic activity, mucin depletion and possibly cryptitis, crypt abscesses or eosinophilia
  • Depending on the timing of the biopsy, regenerating epithelial cells with atypia that may mimic dysplasia may be present
  • Chronic disease shows superficial dilated capillaries with surrounding hyaline fibrosis
  • Dilated lymphatics, fibrosis with atypical (radiation) fibroblasts, atypical endothelial cells, crypt loss and distortion mimicking ischemia and obliterative endarteritis of submucosal arteries (and mesenteric arteries in resection specimens) are usually present
  • Congestion and ulceration may be present; secondary malignancies have been reported
Differential diagnosis
  • Acute radiation proctitis may mimic allergic colitis or eosinophilic colitis but the history will allow accurate diagnosis
  • Ischemic proctitis: may be impossible to distinguish from chronic radiation proctitis without a history, although superficial hyaline perivascular changes and radiation fibroblasts are lacking in ischemic proctitis; in addition, the anal canal has a dual blood supply and is not commonly affected by ischemia
  • Crypt distortion and atrophic changes may mimic idiopathic inflammatory bowel disease but IBS lacks radiation fibroblasts and hyaline vascular changes
  • Vascular changes may mimic portal colopathy or angiodysplasia but other radiation changes are not present
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