Non-gonococcal urethritis (NGU) is an inflammation of the urethra which is not caused by gonorrheal infection.

Urethritis can be caused by a number of organisms, including Neisseria gonorrheae, Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma genitalium, Trichomonas vaginalis, Herpes simplex virus, and Candida albicans, and by a number of non-infectious causes, including urethral stricture, foreign bodies, trauma, Reiter's syndrome, and various autoimmune and allergic conditions.

Of these many causes, the vast preponderance of cases are due to either gonorrhea or chlamydia. It is currently estimated that 50% of NGU cases are caused by chlamydia, with the remainder due to other causes.

It is important to consider, however, the possibility that the commonly accepted contagion theories may be flawed. We can question whether or not a disease is actually 'transmitted' -rather than in some way being 'caused' by some other condition which invites rapid reproduction of opportunist microbes.

Historically, it has been easy to test for the presence of gonorrhea by viewing a Gram's stain of the urethral discharge under a microscope: the causative organism is distinctive in appearance. Thus, one of the major causes of urethritis can be identified by a simple common test, and the distinction between gonococcal and non-gonococcal urethritis arose historically for this reason.

Identifying chlamydia, the other major cause of urethritis, has required more sophisticated technology, but is now more widely available. These two tests combined identify the cause of most treatable forms of urethritis. If tests for gonorrhea and chlamydia are negative, and the cause of the urethritis has not been otherwise identified, the term non-specific urethritis (NSU) is used. The terms "NGU" and "NSU" are sometimes used inconsistently, but these are the most common meanings in the modern era of treatment.

Because of its multi-causative nature, initial treatment strategies involve using a broad range antibiotic that is effective against chlamydia (such as doxycycline). It is imperative that both the patient and any sexual contacts are treated. Women who are infected with the organisms that cause NGU may develop pelvic inflammatory disease. If symptoms persist, follow-up with a urologist may be necessary to identify the cause.

If left untreated, complications include epididymitis and infertility. Consistent and correct use of latex condoms during sexual activity greatly reduces the likelihood of infection.

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