Histology Reveals Characteristics of Superimposed Bacterial Ulcerative Colitis

Biopsy specimens have been examined for histologic features suggestive of Clostridium difficile infection in patients with ulcerative colitis.

In patients with acutely symptomatic ulcerative colitis, it is important to determine whether the underlying cause of the disease is due to a C. difficile infection or may arise due to other infectious organisms and or bowel ischemia.


Pathologists at St Michael’s Hospital (Toronto, ON, Canada) examined nine patients with ulcerative colitis who had colonic biopsy specimens taken during a symptomatic flare that coincided with positive C. difficile (C. difficile+) tests. They also examined 28 controls that were biopsied during an ulcerative colitis flare, but tested negative for C. difficile. The scientists reviewed the histological slides for evidence of pseudomembranes, ischemic-like changes, degree of colitis, and lamina propria hemorrhage. Pseudomembranes are not real membranes: they represent necrotic debris attached to the colonic wall and may vaguely resemble a volcanic eruption, when examined microscopically.

Stool testing was performed using the C. difficile Tox A/B II enzyme immunoassay (EIA) (Techlab; Blacksburg, VA, USA). The results were analyzed with a dual-wavelength spectrometer at 450 nm and 620 nm. In the patients who had a positive C. difficile+ test, four of nine (44.4%) had microscopic pseudomembranes compared with only 11% in controls who were C. difficile negative, which was statistically significant. The investigators found that other histologic and clinical features were not predictive.

The authors concluded that although the presence of microscopic pseudomembranes suggests C. difficile infection in patients with ulcerative colitis, sensitivity and specificity were poor; biopsy findings do not reliably detect this infection in patients with ulcerative colitis. However, the authors propose that histologic findings of microscopic pseudomembranes should also prompt testing for C. difficile if not already performed.

Ulcerative colitis is a form of inflammatory bowel disease (IBD). It is a disease of the colon that includes characteristic ulcers, or open sores. The main symptom of active disease is usually constant diarrhea mixed with blood, of gradual onset. IBD is often confused with irritable bowel syndrome. The study was published in the December 2013 issue of the American Journal of Clinical Pathology.

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