What Causes Proctitis
Proctitis is primarily caused by sexually transmitted infections in individuals who engage in receptive anal intercourse, with Neisseria gonorrhoeae, Chlamydia trachomatis (including lymphogranuloma venereum serovars), Treponema pallidum, and Herpes simplex virus being the most common pathogens. 1, 2
Sexually Transmitted Pathogens (Most Common)
The CDC identifies four primary sexually transmitted pathogens that cause proctitis, particularly in persons who participate in receptive anal intercourse 1, 2:
- Neisseria gonorrhoeae - One of the most frequently implicated organisms in infectious proctitis 1, 2
- Chlamydia trachomatis - Including standard serovars and LGV (lymphogranuloma venereum) serovars, which can cause especially severe proctitis 1, 2
- Treponema pallidum - The causative agent of syphilis, which can manifest as proctitis 1, 2
- Herpes simplex virus - Can cause particularly severe proctitis in HIV-infected individuals 1, 2
Enteric Pathogens Causing Proctocolitis
When inflammation extends beyond the distal 10-12 cm of rectum (proctocolitis), additional pathogens should be considered 1:
- Campylobacter species - Acquired through receptive anal intercourse or oral-anal contact 1, 2
- Shigella species - Particularly common in men who have sex with men 1, 2
- Entamoeba histolytica - Associated with oral-anal contact 1, 2
- LGV serovars of C. trachomatis - Can cause more extensive disease than standard chlamydial serovars 1
Opportunistic Infections in Immunocompromised Patients
In HIV-infected or otherwise immunosuppressed individuals, additional pathogens must be considered 1, 2:
- Cytomegalovirus (CMV) - Can cause severe proctitis in immunosuppressed patients 1, 2
- Mycobacterium avium-intracellulare - Causes enteritis in HIV-infected individuals 1, 2
- Cryptosporidium, Microsporidium, and Isospora - Opportunistic parasites in HIV patients 1, 2
Key Risk Factors and Transmission Routes
Understanding transmission patterns is essential for diagnosis 2, 3:
- Receptive anal intercourse - The primary risk factor for sexually transmitted proctitis 1, 2, 3
- Oral-anal contact - Can transmit enteric pathogens like Giardia lamblia, Entamoeba histolytica, and Shigella 1, 2
- HIV infection status - Significantly affects disease severity, particularly for HSV and CMV proctitis 1, 2
Important Clinical Pitfalls
A detailed sexual history is absolutely crucial - specifically asking about receptive anal intercourse and oral-anal contact, as patients may not volunteer this information 2, 3. The incidence of infectious proctitis has been rising, especially among men who have sex with men, making it essential to distinguish from inflammatory bowel disease 4, 5, 6.
HIV testing should be performed in all patients with infectious proctitis, as HIV status fundamentally affects both treatment approach and prognosis 2, 7, 3. Herpes proctitis can be especially severe in HIV-infected individuals and requires closer monitoring 2, 7.
Consider coinfections - multiple sexually transmitted pathogens can occur simultaneously, and all patients should be tested for the four primary STI pathogens plus HIV and syphilis 2, 7, 3.