Sexually Transmitted Infections of the Colon—Clinical Picture, Endoscopic Features, and Laboratory Diagnosis: A Practical Review for the General Practitioner

Sexually transmitted infections (STIs) are common and probably underreported causes of proctitis and colitis. Bacterial (chlamydia, gonorrhoea, syphilis, Mycoplasma genitalium), viral (herpes simplex virus, mpox), and amoebic (Entamoeba histolytica) pathogens can cause inflammatory proctitis or colitis, which, depending on the pathogen, can mimic inflammatory bowel disease both on endoscopy and histopathology. Rectal and colonic masses are uncommon, but important manifestations of these infections, especially with chlamydia, syphilis, and E. histolytica. Testing for HIV is important in this context, since it allows for the inclusion of opportunistic pathogens into the differential diagnosis. Chronic diarrhoea can be a feature of chronic HIV infection. Enteric pathogens, such as Salmonella spp., Shigella spp., or Campylobacter spp., can be transmitted during sex, especially during oral–anal contact (“rimming”). The most common STI, human papillomavirus, is not associated with colitis, but is important because of its causal association with genital warts and anal cancer.