|Classification and external resources|
For treatment purposes, doctors usually classify infectious urethritis in two categories: gonococcal urethritis, caused by gonorrhea, and nongonococcal urethritis (NGU).
Parasitic causes include Trichomonas vaginalis (rare).
The symptoms of urethritis can include pain or a burning sensation upon urination (dysuria), a white/cloudy discharge and a feeling that one needs to pass urine frequently. For men, the signs and symptoms are discharge from the penis, burning or pain when urinating, itching, irritation, or tenderness, and underwear stain. In women, the signs and symptoms are discharge from vagina, burning or pain when urinating, anal or oral infections, abdominal pain, or abnormal vaginal bleeding, which may be an indication that the infection has progressed to Pelvic Inflammatory Disease. However, men are frequently, and women are known to be affected with cervicitis and pelvic inflammatory disease Template:PMID 16462559
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; however, this works only with men because other non-pathogenic gram-negative microbes are present as normal flora of the vagina in women. Thus, one of the major causes of urethritis can be identified (in men) by a simple common test, and the distinction between gonococcal and non-gonococcal urethritis arose for this reason.
Non-gonococcal urethritis (NGU) is diagnosed if a person with urethritis has no signs of gonorrhea bacteria on laboratory tests. The most frequent cause of NGU (23%-55% of cases) is chlamydia.
Non-specific urethritis 
In the United Kingdom, NGU is more often called non-specific urethritis; "non-specific" is a medical term meaning "specific cause has not been identified", and in this case refers to the detection of urethritis, and the testing for but found negative of gonorrhea. In this sense, the most likely cause of NSU is a chlamydia infection.
However, the term NSU is sometimes distinguished and used to mean that both gonorrhea and chlamydia have been ruled out. Thus, depending on the sense, chlamydia can either be the most likely cause or have been ruled out, and frequently detected organisms are ureaplasma urealyticum and mycoplasma hominis.
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 be treated. Women 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.
A completed "November 19, 2009" Phase II Randomized, Placebo-Controlled Double-Blind 4-Arm Trial for the Treatment of Non-Gonococcal Urethritis (NGU): Doxycycline (Plus or Minus Tinidazole) Versus Azithromycin (Plus or Minus Tinidazole). Purpose of the study was to look at the safety, effectiveness, and tolerability of combination medications for the initial treatment of non-gonococcal urethritis (NGU). This study compared the 2 currently recommended NGU treatments, doxycycline and azithromycin, taken with tinidazole (another medication to treat certain sexually transmitted infections). Tinidazole used with doxycycline or azithromycin may cure NGU better than when doxycycline or azithromycin is used alone.
See also 
- Burstein GR, Zenilman JM (January 1999). "Nongonococcal urethritis—a new paradigm". Clin. Infect. Dis. 28 (Suppl 1): S66–73. doi:10.1086/514728. PMID 10028111.
- Bradshaw CS, Tabrizi SN, Read TR, et al (February 2006). "Etiologies of nongonococcal urethritis: bacteria, viruses, and the association with orogenital exposure". J. Infect. Dis. 193 (3): 336–45. doi:10.1086/499434. PMID 16388480.
- Non-specific urethritis, NHS
- Non-specific Urethritis (NSU), NHS, Genito-Urinary Medicine (GUM)
- NSU (non-specific urethritis), BBC
- Non-specific urethritis (NSU) and Cervicitis
- "Nongonococcal Urethritis (NGU)". BC HealthFile. Retrieved 2008-01-01.
- ClinicalTrials.gov NCT00322465 NGU: Doxycycline (Plus or Minus Tinidazole) Versus Azithromycin (Plus or Minus Tinidazole)