Can Clostridioides difficile (C. diff) cause proctitis without colitis?

C. difficile Proctitis Without Colitis

C. difficile infection rarely causes isolated proctitis without colitis, as it typically affects the entire colon or predominantly the proximal colon rather than being limited to the rectum. The typical presentation of C. difficile infection involves diffuse colonic involvement with pseudomembranous colitis being the hallmark finding in severe cases 1.

Pathophysiology and Distribution of C. difficile Infection

C. difficile produces toxins A and B that cause colonic mucosal injury and inflammation 2. These toxins typically affect the entire colon, with several characteristic patterns:

• Most commonly presents as pancolitis or predominantly right-sided/proximal colitis
• Pseudomembranous plaques are pathognomonic but relatively infrequent 3
• In IBD patients, typical inflammatory findings of CDI on colonoscopy are often absent due to a weakened inflammatory response 2

Diagnostic Patterns

The 2019 WSES guidelines describe several radiological findings in C. difficile colitis 1:

• Colonic wall thickening (most common finding)
• "Accordion sign" (alternating areas of high and low attenuation in the colonic lumen)
• "Double-halo sign" or "target sign" (varying degrees of attenuation caused by submucosal inflammation)

Isolated Proctitis vs. Colitis

The literature does not support C. difficile as a common cause of isolated proctitis:

1. C. difficile typically causes extensive colonic involvement rather than isolated rectal disease 1, 2
2. In IBD patients with C. difficile, the infection pattern typically shows extensive colitis rather than proctitis alone 1
3. When C. difficile affects the rectum, it generally does so as part of more extensive colonic involvement 4

Special Considerations in IBD Patients

In patients with inflammatory bowel disease, C. difficile infection has some unique characteristics:

• C. difficile can trigger flares of IBD and complicate the clinical picture 1
• IBD patients show high rates of asymptomatic C. difficile colonization 2
• Typical pseudomembranes may be absent in IBD patients with C. difficile infection 1
• Symptoms of C. difficile infection and IBD flare overlap, making diagnosis challenging 2

Diagnostic Approach

When suspecting C. difficile infection:

1. Stool testing for C. difficile toxins and glutamate dehydrogenase antigen (GDH) is the first-line diagnostic approach 4
2. Nucleic acid amplification testing (NAAT) may be needed if initial tests are negative but suspicion remains high 4
3. Endoscopic evaluation may be required in rare instances with high clinical suspicion despite negative testing 4
4. Flexible sigmoidoscopy may be helpful in diagnosis when there is high clinical suspicion for C. difficile infection but stool assays are negative 1

Clinical Implications

If a patient presents with isolated proctitis, consider alternative diagnoses before attributing it to C. difficile:

• Inflammatory bowel disease (particularly ulcerative proctitis)
• Other infectious causes of proctitis
• Radiation proctitis
• Sexually transmitted infections affecting the rectum

Conclusion

Based on the available evidence, C. difficile infection rarely manifests as isolated proctitis without colitis. The typical pattern involves more extensive colonic involvement, particularly affecting the proximal colon. When evaluating a patient with isolated proctitis, clinicians should consider alternative diagnoses while still testing for C. difficile if clinically indicated.