Question
Non-gonococcal urethritis
Answer
Non-gonococcal urethritis (NGU) refers to urethritis caused by an organism other than Neisseria gonorrhoeae — the most important sexually transmitted cause of urethral discharge/dysuria after gonococcal urethritis, and now the more common of the two in many settings.
Causative organisms:
- Chlamydia trachomatis (serovars D–K) — the single most common cause of NGU.
- Ureaplasma urealyticum and Mycoplasma genitalium — important causes, particularly in recurrent/persistent NGU.
- Trichomonas vaginalis, and, less commonly, herpes simplex virus, adenovirus.
Clinical features: typically a milder, more mucoid/less purulent discharge than gonococcal urethritis, with a longer incubation period (1–3 weeks vs. 2–7 days for gonorrhoea), and can be asymptomatic in a significant proportion of infected individuals (particularly women) — an important reservoir for continued transmission. Untreated chlamydial infection can ascend to cause epididymitis in men and pelvic inflammatory disease, tubal infertility, and ectopic pregnancy in women.
Laboratory diagnosis: Gram stain of urethral discharge shows pus cells without intracellular Gram-negative diplococci (distinguishing it from gonococcal urethritis, where intracellular Gram-negative diplococci are seen); nucleic acid amplification test (NAAT/PCR) on urethral swab or first-void urine is the current gold standard for chlamydia detection; cell culture (McCoy cells) is the older reference method but rarely used now; testing should also screen for concurrent gonococcal infection, since co-infection is common.
Treatment: azithromycin (single dose) or doxycycline for chlamydial NGU; treatment of sexual partners; screening/treatment for other coexisting STIs.