Non-specific urethritis is the name given to the situation when a man has an excess of polymorphonuclear leucocytes (PMNL) in his urethra, but tests for specific infections are negative. What constitutes non-specific urethritis therefore depends on the definition of an ‘excess of polymorphonuclear leucocytes’ and which specific infections you have tested for.
genitourinary medicine physicians have heated debates about how many polymorphonuclear leucocytes constitute an ‘excess’. The generally accepted figure is that if you are doing Gram-stained microscopy of a smear of material taken from a man’s urethra, then >5 PMNL per microscope field at x1000 magnification is abnormal.
If you are doing microscopy on a ‘thread’ specimen taken from a first-void urine specimen, the cut-off is >10 PMNL per microscope field at x1000 magnification.
Most STI clinics, lets call them type A clinics, just test male urethras for chlamydia and gonorrhoea. If a man has urethritis but those tests are negative, then he has non-specific urethritis. Other clinics, let’s call them type B clinics, also test for mycoplasma and trichomoniasis. Again, a full set of negative tests means that the man has non-specific urethritis. As you can see, non-specific urethritis diagnosed at clinic A is a different beast from that diagnosed at clinic B. So what causes urethritis that is not due to chlamydia or gonorrhoea? Numerous conditions are suspected and sometimes proven to be associated with non-specific urethritis, as shown in Table Possible causes of non-specific urethritis.
Table Possible causes of non-specific urethritis
|Sexually transmitted infections||Infections that are probably not sexually transmitted||Other conditions|
|Approximate proportion of cases of non-specific urethritis||85%||10%||5%|
|Condition||Chlamydia or gonorrhoea with a false-negative test, Mycoplasma genitalium, Ureaplasma urealyticum, Trichomonas vaginalis, herpes simplex viruses||Adenoviruses, urinary tract infections, Candida albicans, Neisseria meningitidis, chronic bacterial prostatitis||Contact urethritis (e.g. from shower gel), foreign bodies, urethral stricture, chronic pelvic pain syndrome (inflammatory)|
Due to the uncertain significance of non-specific urethritis and increased demands on time, some genitourinary medicine clinics are stopping doing microscopy on asymptomatic men, arguing that those with chlamydia or gonorrhoea will be picked up by the laboratory tests and that there is insufficient evidence of the benefit of treating other causes of urethritis. Further research might clarify the situation — it might reveal that U. urealyticum, for example, is definitely associated with a late complication such as infertility and thus screening for it is useful.
Non-gonococcal urethritis (NGU) is a term that is sometimes (incorrectly) used interchangeably with non-specific urethritis. As the name suggests, NGU is urethritis when the tests for gonorrhoea are negative. About 40% of cases of NGU are due to chlamydia.
Non-specific urethritis and non-gonococcal urethritis are only diagnosed in men; the equivalent diagnosis in women is nonspecific cervicitis, although this diagnosis is rarely made in practice. This is because it is even more difficult to confidently judge what constitutes an excess of polymorphonuclear leucocytes on a specimen from the cervix.
Presentation of Non-Specific Urethritis
Most men with non-specific urethritis are asymptomatic and are diagnosed when they present to a genitourinary medicine clinic looking for an STI screen.
Some men with non-specific urethritis have symptoms such as dysuria, discharge (usually scanty or clear) or vague feelings of urethral irritation. The men with non-specific urethritis that GPs encounter are more likely to be in this latter group. Merely having symptoms is not enough to diagnose non-specific urethritis; in the absence of microscopic evidence of urethritis, dysuria might just be due to urethral irritation (see Dysuria and urethral discharge).
Complications of Non-Specific Urethritis
These depend on the causative organism or condition, although by definition, in non-specific urethritis the cause is not known. Possibilities include Reiter’s syndrome, epididymo-orchitis and transmission to women leading to premature labour (T. vaginalis) or infertility (chlamydia).
Diagnosis of Non-Specific Urethritis
The diagnostic criteria for non-specific urethritis are described in the introduction. The longer a man holds his urine, the greater the sensitivity of the test. An absolute minimum hold is 1 hour, but a hold of more than 4 hours is better. If microscopy is normal after this delay, a symptomatic man should be asked to return having held his urine overnight. The specimen should be collected using a small tipped swab or a plastic loop. This material should then be smeared over about 0.5 cm2 of a microscope slide and sent to the lab for microscopy.
Dipstick urinalysis of a first-void urine specimen can sometimes reveal leucocytes, but this is a less sensitive test for urethritis. If the patient has urinary frequency, urgency or haematuria, a midstream specimen of urine should be taken and sent for microscopy, culture and sensitivity.
Chlamydia and gonorrhoea should be excluded.
Treatment of Non-Specific Urethritis
Standard treatments for Chlamydia trachomatis are usually effective for non-specific urethritis. For example:
• azithromycin 1 g p.o. once
• or doxycycline 100 mg p.o. b.d. for 7 days.
Some people have persistent symptoms despite taking treatment correctly and not having sex with untreated partners. The cause of these symptoms is unknown. If urethritis is confirmed by microscopy the patient should be offered second-line treatment with:
• erythromycin 500 mg four times a day for 2 weeks
• and metronidazole 400 mg twice a day for 5 days.
If the patient has a history of flow abnormality or a ‘blockage’ in the urethra, he could be referred for urological assessment using urethroscopy as a check for a urethral stricture or foreign body.
Most causes of non-specific urethritis are sexually transmitted infections, so the patient’s sexual contacts need to be seen. Because there are no useful definitive tests to see if a partner has acquired the causative agent, they should be offered treatment epidemiologically.
If the man is asymptomatic, all sexual contacts within the previous 6 months should be seen. If he is symptomatic, going back 4 weeks prior to the onset of symptoms should be enough. Contacts should have a history taken and be offered treatment with a first-line agent as documented above. They should abstain from sex until both partners have finished treatment.
If symptoms persist in the index case following adequate treatment of the couple, the contact does not need to be retreated.
Information about non-specific urethritis should be given. If the non-specific urethritis is thought to be sexually acquired, the patient should be offered tests for other STIs including HIV.