Nongonococcal urethritis (NGU) is an inflammation of the urethra that is not caused by gonorrheal infection. For treatment purposes, doctors usually classify infectious urethritis in two categories: gonococcal urethritis, caused by gonorrhea, and nongonococcal urethritis (NGU). There are many causes of NGU. This is in part due to the large variety of organisms living in the urinary tract. Ureaplasma urealyticum and Mycoplasma genitalium are some of the culprits. The most common bacterial cause of NGU is Chlamydia trachomatis, but it can also be caused by Ureaplasma urealyticum, Haemophilus vaginalis, and Mycoplasma genitalium. Herpes simplex virus (rare), Adenovirus, Parasitic causes include Trichomonas vaginalis (rare). Urethritis can be caused by mechanical injury (from a urinary catheter or a cystoscope), by an irritating chemical (antiseptics or some spermicides).
Contributions by Arcadian, Karada, and Jmh649.