GPAtlas🧭 When to suspect
Non-gonococcal urethritis (NGU) is inflammation of the urethra in which gonorrhoea has been excluded – confirmed by an excess of polymorphonuclear leucocytes in the anterior urethra without Gram-negative intracellular diplococci. It is one of the commonest reasons men attend sexual-health services, typically presenting with urethral discharge, dysuria and/or penile-tip irritation, though it can be asymptomatic. Suspect it in any sexually active man (or person with a penis), particularly with a new partner, multiple partners, or condomless sex.
Chlamydia trachomatis is the commonest identified cause; Mycoplasma genitalium is increasingly important and is the dominant cause of persistent or recurrent NGU. In a large minority (~10–45%) no organism is found (idiopathic NGU), and some of these are non-infective. Because gonococcal and non-gonococcal urethritis are indistinguishable on symptoms, NGU is a diagnosis made only after gonorrhoea has been excluded – so testing is essential.
The key skill in primary care is to recognise the syndrome, exclude the red flags (epididymo-orchitis, systemic illness, reactive arthritis), test (including for gonorrhoea, to confirm this really is NGU), and route the patient into sexual-health care – where microscopy confirmation, a full STI screen, partner notification and resistance-guided treatment can all happen. Comprehensive care is the goal, not a quick prescription.
| Cause of NGU | Notes |
|---|---|
| Chlamydia trachomatis | The commonest identified cause (~20–50% of NGU). |
| Mycoplasma genitalium | ~15–25%; the key driver of persistent/recurrent NGU; needs resistance-guided treatment. |
| Ureaplasma urealyticum | Inconsistent association – usually only at high organism load. |
| Trichomonas vaginalis | Uncommon in the UK (< 2%); consider in men who have sex with women, especially where locally prevalent. |
| Adenovirus / herpes simplex | Viral – often with meatitis, conjunctivitis or ulceration; usually self-limiting. |
| Haemophilus spp. / Neisseria meningitidis | Recognised pathogens (new in 2026); may follow condomless oral sex. |
| Organism-negative (idiopathic) | No pathogen found in ~10–45%; some non-infective (trauma, foreign body, stricture, chemical irritation). |
Source: BASHH NGU 2026
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