NSU (non-specific urethritis) Dr Rob Hicks Non-specific urethritis (NSU) is a sexually transmitted infection that occurs in men.

In this article

What is it? What are the symptoms?

Who's affected? How's it diagnosed?

What's the treatment?

Non-specific urethritis (NSU) is also sometimes known as non-gonococcal urethritis (NGU).

It describes inflammation of the urethra (the tube in the penis that carries urine from the bladder out of the body) when the cause it not known and when gonorrhoea has been ruled out as a cause.

In almost 50 per cent of cases, further testing identifies the bacteria chlamydia as the underlying cause. Other organisms that may be responsible include:

• Human papilloma virus (HPV), which causes genital warts
• Herpes simplex virus (HSV), which causes genital herpes
• Trichomonas vaginalis, a protozoan that causes trichomoniasis

A man with NSU may experience a burning or uncomfortable sensation when passing water, particularly first thing in the morning, a slight, white, cloudy fluid discharge from the penis, a general vague discomfort of the penis, and redness/soreness at the opening of the urethra.

However, the infection may not lead to any symptoms at all. When this is the case the infection may go undetected until it causes additional problems such as prostatitis (inflammation of the prostate gland), epididymo-orchitis (inflammation of the testes and the epididymis, the curly tubes that carry and store sperm), or arthritis.

If these complications do not develop then it may also only be detected when a man's partner develops symptoms of a possible sexually transmitted infection (STI).

Possible symptoms of NSU

• Burning or discomfort when passing water
• Vague penile discomfort
• Redness and soreness at urethral opening
• Some men have no symptoms

NSU is one of the most common STIs in men. Men of any age can be affected. They're at an increased risk of contracting it, and other STIs, if they practise unprotected sex with multiple partners.

Women who are infected by a man with NSU are at risk from chlamydia, which can lead to pelvic inflammatory disease and cause infertility.

When NSU is suspected, the diagnosis is confirmed by taking a swab from the urethra and by testing a urine sample. Other STIs will be tested for at the same time.

It's important that sexual partners are tested too, otherwise the infection may be passed straight back.

The infection is easily treated with antibiotic, antiviral or antifungal medication depending on which organism is causing the problem. Whilst taking the treatment, and until the infection has been cleared, it's best to avoid sexual contact.

This article was last medically reviewed by Dr Rob Hicks in December 2007