Introduction

A wide variety of microbial pathogens may be transmitted sexually by the oral–anal or genital–anal routes. Sexually transmitted enteric infections may involve multiple sites of the gastrointestinal tract, resulting in proctitis, proctocolitis, and enteritis. These infections occur primarily in men who have sex with men (MSM) and heterosexual women who engage in anal–rectal intercourse or in sexual practices that allow for fecal–oral transmission. Anorectal infections with syphilis, gonorrhea, condyloma acuminata (human papillomavirus, HPV), lymphogranuloma venereum (LGV), and granuloma inguinale (donovanosis) have been recognized for many years. Over the past 2 decades, other sexually transmitted pathogens such as herpes simplex virus (HSV) and Chlamydia trachomatis have also been recognized as causing anorectal infection. Enteric pathogens traditionally associated with food or waterborne acquisition but that also may be transmitted sexually include Giardia lamblia, Entamoeba histolytica, Campylobacter, Shigella, and Salmonella. In patients with acquired immunodeficiency syndrome (AIDS), other opportunistic infections, including Candida, Microsporida, Cryptosporidium, Isospora, Cyclospora, Mycobacterium avium complex, and cytomegalovirus (CMV), may also cause intestinal disorders.

Depending on the pathogen and the location of the infection, symptoms and clinical manifestations vary widely. Perianal lesions are usually caused by syphilis, HSV, granuloma inguinale, chancroid, and condyloma acuminata. Rectal infections cause inflammation of the rectal mucosa, commonly referred to as proctitis. Symptoms include constipation, tenesmus, rectal discomfort or pain, hematochezia, and a mucopurulent rectal discharge. Proctitis can be caused by gonorrhea, chlamydia, syphilis, and HSV. Proctocolitis involves inflammation extending from the rectum to the colon, and in addition to the organisms causing proctitis, other enteric pathogens such as Shigella, Salmonella, Campylobacter, E. histolytica, and CMV may be involved. Enteritis is an inflammatory illness of the duodenum, jejunum, and/or ileum. Sigmoidoscopy results are often normal, and symptoms consist of diarrhea, abdominal pain, bloating, cramps, and nausea. Additional symptoms may include fever, weight loss, myalgias, flatulence, urgency, and, in severe cases, melena. Sexually transmitted pathogens usually associated with enteritis include Shigella, Salmonella, Campylobacter, Giardia, CMV, and, potentially, Cryptosporidium, Isospora, and Microsporida.