C. difficile and Pseudomembranous Colitis: Relationship and Distinctions
Clostridioides difficile (C. diff) is not the same as pseudomembranous colitis, but rather C. diff infection is the most common cause of pseudomembranous colitis. Pseudomembranous colitis represents a specific endoscopic and histopathological finding that can occur in severe cases of C. diff infection.
Relationship Between C. diff and Pseudomembranous Colitis
Definitions and Distinctions
- C. difficile: A toxin-producing bacterium that causes intestinal infection, primarily after antibiotic use disrupts normal gut flora 1
- Pseudomembranous colitis: A severe manifestation of colonic inflammation characterized by the presence of yellowish-white plaques or "pseudomembranes" on the colonic mucosa 1
Key Points
- Pseudomembranous colitis is a finding that indicates severe colonic inflammation 1
- While C. diff is the most common cause of pseudomembranous colitis, it is present in only about 13% of C. diff infection cases 2
- C. diff infection presents as a spectrum of disease severity ranging from asymptomatic colonization to mild diarrhea to severe pseudomembranous colitis 1
Diagnostic Considerations
Clinical Diagnosis
- C. diff infection requires:
- Diarrhea (≥3 unformed stools in 24 hours)
- Positive stool test for toxigenic C. difficile or its toxins
- OR colonoscopic/histopathologic evidence of pseudomembranous colitis 1
Endoscopic Findings
- Pseudomembranous colitis is visualized during colonoscopy or sigmoidoscopy as white or yellowish plaques covering the colonic mucosa 1, 3
- Direct visualization of pseudomembranes is almost diagnostic of C. diff colitis, but pseudomembranes are only present in:
- 71% of patients with severe C. diff disease
- 23% of patients with mild C. diff disease 4
Laboratory Testing
- C. diff testing typically involves:
- C. difficile toxin and glutamate dehydrogenase antigen screen (GDH)
- Nucleic acid amplification testing (NAAT) if initial screening is negative 2
- Negative C. diff testing in the presence of pseudomembranous colitis should prompt investigation for other causes 5
Other Causes of Pseudomembranous Colitis
Although C. diff is the predominant cause, pseudomembranous colitis can also be caused by:
- Other bacterial infections
- Viral infections (particularly cytomegalovirus)
- Parasitic infections
- Medications and chemicals
- Ischemic colitis
- Inflammatory conditions 5
Clinical Implications
When to Suspect Pseudomembranous Colitis
- Severe diarrhea (especially after antibiotic exposure)
- Abdominal pain and distension
- Fever (>38.5°C)
- Marked leukocytosis (>15 × 10^9/L)
- Signs of severe systemic inflammatory response 1, 4
Diagnostic Approach
- In patients with high clinical suspicion but negative stool tests, endoscopic evaluation may be necessary to visualize pseudomembranes 2, 6
- CT imaging may show colonic wall thickening, dilation, peri-colonic stranding, and other findings suggestive of C. diff colitis 1
Treatment Considerations
- Treatment should be based on disease severity 1
- For severe C. diff infection with pseudomembranous colitis, oral vancomycin is the preferred treatment 1, 7
- Clinical trials with vancomycin show 80-81% success rates in treating C. diff infection 7
- Failure to respond to appropriate treatment should prompt investigation for concomitant conditions, such as cytomegalovirus colitis 3
Common Pitfalls
- Assuming all C. diff infections present with pseudomembranous colitis
- Failing to consider other causes of pseudomembranous colitis when C. diff tests are negative
- Relying solely on laboratory tests without clinical correlation
- Overlooking the possibility of mixed infections (e.g., C. diff with cytomegalovirus) 3
- Testing for C. diff in asymptomatic patients or those with formed stool 1
Remember that while pseudomembranous colitis is strongly associated with C. diff infection, they are not synonymous terms. Pseudomembranous colitis represents a severe manifestation that can occur in C. diff infection but can also be caused by other conditions.