What are the causes of proctitis (inflammation of the lower rectum)?

Causes of Lower Rectum Colitis (Proctitis)

The most common causes of proctitis (inflammation of the lower rectum) are sexually transmitted infections, particularly in individuals who engage in receptive anal intercourse, with Neisseria gonorrhoeae, Chlamydia trachomatis, Treponema pallidum, and Herpes simplex virus being the primary pathogens. 1

Infectious Causes

Sexually Transmitted Infections

• Neisseria gonorrhoeae (gonorrhea) - a common bacterial cause of proctitis in individuals who engage in receptive anal intercourse 1
• Chlamydia trachomatis - including lymphogranuloma venereum (LGV) serovars which can cause particularly severe proctitis 1
• Treponema pallidum (syphilis) - can cause proctitis with characteristic ulcerative lesions 1
• Herpes simplex virus (HSV) - can cause severe proctitis, especially in HIV-infected individuals 1
• Mycoplasma genitalium - increasingly recognized as a cause of infectious proctitis 2

Enteric Pathogens

• Campylobacter species - can cause proctocolitis extending to 12 cm above the anus 1
• Shigella species - associated with proctocolitis, particularly in men who have sex with men 1
• Entamoeba histolytica - parasitic cause of proctocolitis that can be acquired through oral-anal contact 1
• Giardia lamblia - most frequently implicated in enteritis among otherwise healthy individuals who engage in oral-anal contact 1

Opportunistic Infections (particularly in HIV-infected individuals)

• Cytomegalovirus (CMV) - can cause severe proctitis in immunosuppressed patients 1
• Mycobacterium avium-intracellulare - can cause enteritis in HIV-infected individuals 1
• Cryptosporidium, Microsporidium, and Isospora - require special stool preparations for diagnosis 1

Non-Infectious Causes

Inflammatory Bowel Disease

• Ulcerative proctitis - a subtype of ulcerative colitis limited to the rectum 3
• Crohn's disease - can present with isolated proctitis in some cases 2, 4

Other Causes

• Radiation proctitis - following radiation therapy for pelvic malignancies 3
• Medication-induced proctitis - certain medications can cause rectal inflammation 3
• Ischemic proctitis - due to compromised blood flow to the rectum 3
• Direct effect of HIV infection - HIV itself can cause enteritis 1
• Mpox (monkeypox) - recently identified as a cause of proctitis during outbreaks 2

Diagnostic Approach

Clinical Evaluation

• Symptoms typically include anorectal pain, tenesmus, rectal discharge, rectal bleeding, and sometimes constipation or diarrhea 5
• A detailed sexual history is crucial, particularly regarding receptive anal intercourse 5
• HIV status should be assessed, as herpes proctitis can be especially severe in HIV-infected individuals 5

Diagnostic Testing

• Anoscopy should be performed to visualize the rectal mucosa 6, 5
• Gram-stained smear of anorectal exudate should be examined for polymorphonuclear leukocytes 6, 5
• All patients should be tested for:
  • HSV (by PCR or culture) 1, 6
  • N. gonorrhoeae (NAAT or culture) 1, 6
  • C. trachomatis (NAAT) 1, 6
  • T. pallidum (darkfield if available and serologic testing) 1, 6
• If C. trachomatis test is positive, a molecular PCR test for LGV should be performed 1, 6

Clinical Pearls and Pitfalls

• Distinguishing infectious proctitis from inflammatory bowel disease is a significant clinical challenge due to overlap in clinical presentation and endoscopic/histological features 2, 4
• Co-infections are common, particularly among men who have sex with men, so testing for multiple pathogens is recommended 7, 4
• HIV testing should be performed in all patients with infectious proctitis, as HIV status affects treatment approach and prognosis 6, 8
• Sexual partners should be evaluated and treated to prevent reinfection and further transmission 1, 6
• Persistent symptoms after treatment warrant evaluation for reinfection, treatment failure, or alternative diagnoses 5