Radiation Enteritis and Proctitis Workup

Updated: Nov 06, 2019
  • Author: Neelu Pal, MD; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Laboratory Studies

In patients with acute radiation-induced intestinal injury, the complete blood count (CBC) and differential count may be within the reference range. With chronic injury, anemia may be noted because of chronic blood loss and malnutrition. [20] Elevated white blood cell (WBC) counts are observed with small-bowel obstruction and intra-abdominal sepsis because of bowel perforation or necrosis.

Complete metabolic panel results reveal electrolyte abnormalities.

Patients with chronic malnutrition because of malabsorption have abnormal liver function test results and coagulation profiles.


Imaging Studies

In the presence of mild intestinal injury, findings from plain abdominal radiography are nonspecific. Dilated bowel loops with air-fluid levels indicate bowel obstruction. Free air indicates perforation in severe acute or chronic enteropathy, especially in the presence of associated bowel obstruction.

Because most patients have undergone prior surgery, computed tomography (CT) of the abdomen and pelvis is the best study to reveal bowel obstruction. CT may differentiate a partial obstruction from a complete obstruction, as well as define the site of obstruction. Additionally, recurrent malignancy may often be identified. Most patients with obstructive symptoms because of radiation injury present with recurrent, partial obstructions. Patients who present with complete bowel obstructions require surgical exploration and definitive treatment based on the pathology encountered.

Upper gastrointestinal (GI) barium examinations with small intestinal follow-through accurately define the location, extent, and nature of stenotic lesions (see the image below). Mucosal patterns of affected bowel mimic those of inflammatory bowel disease (ie, thickened valvulae conniventes, mural thickening with thumb printing resulting from edema of the submucosa, infiltration of the intestinal wall with fibrotic tissue). Other findings include sinuses and fistulas, variable areas of barium pooling, and rapid intestinal transit of contrast agents.

Contrast study of the small bowel revealing areas Contrast study of the small bowel revealing areas of extensive strictures with a loop of bowel fixed in the pelvis.

Other Tests

Radiation-induced enteric injury leads to extensive intestinal functional abnormalities, resulting in decreased bile acid and vitamin B12 absorption, increased fecal fat excretion, and increased lactose malabsorption. These factors combine to cause rapid small-intestine and whole-gut transit, resulting in chronic diarrhea. Decreased bile salt reabsorption causes a cathartic reaction in the colon, contributing to diarrhea. Bile acid breath tests or direct measurement of bile acids in stool may be used to evaluate the alteration in bile salt metabolism by colonic bacteria.

Selenium-75 homocholic acid taurine (SeHCAT) is a synthetic conjugated bile acid that is resistant to deconjugation and dehydroxylation. SeHCAT may be used to evaluate the active transport of bile acids in the terminal ileum. Patients with poor SeHCAT absorption and retention respond well to cholestyramine treatment. SeHCAT may also be used to evaluate the effectiveness of antidiarrheal agents in reducing transit time and in improving bile acid reabsorption.



Endoscopy is generally avoided in the acute phases of radiation enteritis because of the risk of perforation. Colonoscopy may be necessary to establish a diagnosis or to treat hemorrhage. In these instances, endoscopy is performed cautiously, with minimal bowel insufflation. The intestinal and rectal mucosa is friable and edematous, with areas of superficial ulceration. In severe acute radiation injury, the mucosa may be intensely inflamed, with diffuse duskiness, edema, and extensive ulcerations (see the image below).

Diffuse inflammation and areas of superficial ulce Diffuse inflammation and areas of superficial ulceration observed endoscopically in acute radiation enteritis.

Pale, thin, friable mucosa with prominent submucosal telangiectasias characterizes the endoscopic findings in chronic radiation enteropathy. Smooth, symmetric strictures and areas of ulcerations and fistulas may be identified endoscopically. Bowel-wall biopsy samples are often necessary to differentiate areas of radiation injury from recurrent or de-novo malignancy.

Small-bowel capsule endoscopy is increasingly used to reveal areas of bleeding within the small bowel that are not accessible with traditional endoscopy. Although described in the literature, the use of capsule endoscopy to reveal strictures and fistulas is controversial. The capsule endoscope may become impacted in a stenotic area, risking complete bowel obstruction; therefore, in instances of bowel obstruction, the usefulness of small-bowel capsule endoscopy is limited.


Histologic Findings

Mucosal inflammation with necrosis and ulceration characterize the histologic findings of acute enteritis and colitis. These findings usually appear within 2 weeks after cessation of therapy and gradually resolve over the next few months with mucosal regeneration. The epithelial cells lining the intestinal crypts demonstrate marked enlargement with depletion of mucin and large atypical nuclei.

Despite the intense inflammatory reaction, the general mucosal architecture is preserved, the low nuclear-cytoplasmic ratio is preserved, and no mitotic figures are present. These features help distinguish the radiation-injured intestine from malignancy.

The hallmarks of chronic radiation-induced intestinal injury are as follows:

  • Obliterative arteritis
  • Connective tissue fibrosis
  • Atrophy of the overlying mucosa

The blood vessels in the lamina propria and submucosa are ectatic with intimal fibroplasias, accumulation of foamy macrophages, and hyalin thickening of the vessel walls. All of these changes effectively result in luminal stenosis. Fibrosis of the connective tissue of the submucosa, muscularis propria, and serosa has a hyalinized appearance with large, atypical radiation fibroblasts. The appearance of these cells is typical of, though not pathognomonic for, radiation-induced injury.

Many of the delayed complications of radiation exposure may be attributed to the ischemia related to vascular changes.



The Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC) developed a scoring system for organ-specific radiation-related morbidity according to symptom severity (see Table 1 below).

Table 1. Scoring System for Organ-Specific Radiation-Related Morbidity (Open Table in a new window)


Grade 0

Grade 1

Grade 2

Grade 3

Grade 4

Grade 5

Signs and symptoms


Mild diarrhea, mild cramping, bowel movements 5 times per day, slight rectal discharge or bleeding

Moderate diarrhea and colic, bowel movements >5 times per day, excessive rectal mucus or intermittent bleeding

Obstruction or bleeding requiring surgery

Necrosis, perforation, fistula

Death directly related to late effects of radiation