Non-specific urethritis - Causes 

Some of the possible causes of non-specific urethritis (NSU) are explained below. For urethritis that is caused by gonorrhoea, see the Health A-Z topic about Gonorrhoea.

Chlamydia

The sexually transmitted infection (STI) chlamydia is thought to be responsible for almost half of all cases of NSU in men. In women, about 4 out of 10 cases of NSU may be caused by chlamydia.

Chlamydia is caused by Chlamydia trachomatis bacteria and is spread during unprotected sex, including anal and oral sex. See the Health A-Z topic about Chlamydia for more information about this condition.

Other infections

A number of other infections can cause NSU.

This includes other bacteria that usually live harmlessly in the throat, mouth or rectum (where waste material is stored and passed from the body). They can cause NSU if they manage to find their way into the urethra, which is the tube that carries urine from the bladder to the outside of the body. This can often occur during oral or anal sex.

Possible infections that can cause NSU include:

• Trichomonas vaginalis, which is an STI caused by a tiny parasite
• other bacteria, for example Mycoplasma
• a urinary tract infection 
• the herpes simplex virus, which can also cause cold sores and genital herpes 
• an adenovirus, which usually causes a sore throat or an eye infection

Non-infectious causes

It is possible for NSU to have a non-infectious cause. This is when something else leads to the urethra becoming inflamed (red and swollen). Non-infectious causes of NSU include:

• irritation from a product used in the genital area, such as soap, deodorant or spermicide
• damage to the urethra caused by vigorous sex or masturbation
• damage to the urethra caused by inserting an object into it, for example when a catheter (thin, plastic tube) is inserted to allow urine to drain from the bladder, for example during an operation in hospital