Non-specific urethritis (NSU) is inflammation of the urethra, which is the tube that carries urine.
It is tested for in men with symptoms (for example pain on passing urine, redness and itching of the urethra or discharge).
There are multiple different causes, ranging from STIs to an adverse reaction to cleaning products or a non-STI bacterial infection.
If gonorrhoea has been ruled out as a cause, it can be called non-gonococcal urethritis (NGU). It is usually treated with antibiotics. Your partner(s) will also need to be treated.