Endoscopy in C. difficile Infection
Flexible sigmoidoscopy may be helpful for diagnosing C. difficile infection when there is high clinical suspicion and negative stool tests, but endoscopy should be used sparingly since diagnosis can usually be made by laboratory tests, clinical findings, and imaging. 1
When Endoscopy IS Indicated
Flexible sigmoidoscopy is appropriate in the following situations:
High clinical suspicion with negative stool assays - Sigmoidoscopy should be considered in hospitalized patients with diarrhea when stool tests for C. difficile cytotoxin and enteric pathogens are negative 1
Urgent diagnosis needed - When rapid diagnosis is essential in patients presenting acutely with bloody diarrhea, flexible sigmoidoscopy with mucosal biopsy can differentiate C. difficile colitis from other causes of acute colitis 1
Identifying pseudomembranous colitis - Endoscopic visualization of pseudomembranes (yellow-white plaques on the colonic mucosa) is a marker of severe colitis and can suffice for diagnosis in the absence of another obvious cause 1, 2
Assessing severity markers - Colonoscopy or sigmoidoscopy can identify pseudomembranous colitis as a marker of severe disease, though the correlation of other endoscopic findings (edema, erythema, friability, ulceration) with disease severity is unclear 1
Critical Safety Considerations
Colonoscopy is hazardous in fulminant colitis due to increased perforation risk - Full colonoscopy should be avoided in severe or fulminant colitis settings 1
In acute severe colitis, flexible sigmoidoscopy is sufficient - Complete ileocolonoscopy is not usually recommended due to perforation risk, and bowel purgatives (especially fleet enemas and oral sodium phosphate preparations) should be avoided 1
One study showed no relationship between complication rate and disease activity during endoscopy, suggesting sigmoidoscopy can be safely performed to establish UC diagnosis, though this applies more broadly to inflammatory bowel disease rather than specifically to C. difficile 1
Preferred Diagnostic Approach
Laboratory testing and imaging should be prioritized over endoscopy:
Diagnosis can usually be made by laboratory tests (stool toxin assays, PCR for toxin genes), clinical findings, and imaging 1
CT imaging findings include colonic wall thickening >4mm, accordion sign, pericolonic stranding, and unexplained ascites 1
Point-of-care ultrasound may be useful in critically ill patients who cannot be transported to CT, showing thickened colonic wall with heterogeneous echogeneity and hyperechoic pseudomembranes 1
Clinical Context
Endoscopy was used as a diagnostic criterion in clinical trials - In vancomycin trials for C. difficile-associated diarrhea, patients were enrolled based on ≥3 loose/watery bowel movements within 24 hours AND either C. difficile toxin A or B positivity OR pseudomembranes on endoscopy within 72 hours preceding enrollment 3
Patients with fulminant disease were excluded from these trials - Those with sepsis with hypotension, ileus, peritoneal signs, or severe hepatic disease were not included, reinforcing that endoscopy in severe disease carries significant risk 3
Common Pitfalls to Avoid
Do not perform full colonoscopy in suspected severe/fulminant colitis - The perforation risk outweighs diagnostic benefit 1
Do not use aggressive bowel preparation - Fleet enemas and oral sodium phosphate should be avoided in acute colitis 1
Do not rely solely on endoscopy when stool tests are available - Endoscopy should be reserved for cases where non-invasive testing is negative or inconclusive 1
Recognize that absence of pseudomembranes does not exclude C. difficile - Pseudomembranes may be absent in IBD patients with C. difficile infection 1