Chlamydia trachomatis is the most common sexually transmitted bacterial infection worldwide. The bacterium must live and reproduce within human cells. It causes pelvic inflammatory disease in women and prostatitis in men.  It can cause blindness, infertility and proctitis, or inflammation of the rectum in men and women.  In the United States, male homosexuals account for the majority of rectal Chlamydial infections. Anorectal Chlamydia infection can cause proctitis, or lymphogranuloma venereum (LGV). Transmission of disease is through anoreceptive intercourse, with an incubation period ranging from 5 days to 2 weeks; secondary involvement can also occur as a late manifestation of genital infection.

Symptoms of non-LGV anorectal infection include rectal pain, tenesmus or urgency, and fever, although many infected patients will be asymptomatic. Patients with LGV also complain of pain, fever and tenesmus but often have a bloody, purulent discharge. The inguinal lymph nodes in both types of infection are enlarged and tender, but LGV are often more enlarged as they fuse into a large, red, swollen mass.  LGV can progress to fistulae, abscesses and late rectal strictures if left untreated.

Diagnosis by culture can be difficult, since the bacteria must live within human cells. Diagnosis is generally made on the basis of presentation, identification of proctitis on sigmoidoscopy and a gram stain evaluation under a microscope.

Treatment of a standard Chlamydia infection is with a single oral dose of Azithromycin (1 gm) or doxycylcine (100 mg) twice a day for 7 days. Treatment of LGV is a 21-day course of either erythromycin or doxycycline.  Sexual partners also require treatment to prevent reinfection.