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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Age <35 (sexually active): likely STI — Chlamydia trachomatis (commonest) or Neisseria gonorrhoeae. Treat empirically
- Age >35: likely urinary tract organisms (E. coli, coliforms). Associated with UTIs, catheterisation, urological instrumentation
- Gradual onset scrotal pain and swelling (days, not seconds/minutes like torsion) with fever, dysuria
- Prehn sign positive: elevation of testis relieves pain (unlike torsion). Cremasteric reflex usually preserved
- Treatment: doxycycline 100 mg BD + ceftriaxone 500 mg IM stat if STI suspected (or ofloxacin 200 mg BD for 14 days if enteric organisms)
Overview
Epididymo-orchitis is inflammation/infection of the epididymis and testis. It is the commonest cause of acute scrotal pain in adults (unlike adolescents where torsion is more common). In sexually active men under 35, the cause is usually sexually transmitted organisms (C. trachomatis is the commonest, followed by N. gonorrhoeae). In men over 35 and in children, enteric Gram-negative organisms (E. coli) are more common, often associated with UTIs, BPH, catheterisation, or urological procedures. Viral orchitis (mumps) can occur in post-pubertal males — typically causes isolated orchitis without epididymitis.
Epidemiology
Epididymitis is the fifth most common urological diagnosis in men aged 18–50. Sexually transmitted epididymitis mirrors the epidemiology of chlamydia and gonorrhoea. Mumps orchitis occurs in approximately 30% of post-pubertal males with mumps and is bilateral in ~20% — can cause subfertility. Chronic epididymitis (symptoms >3 months) may develop in up to 15% of cases.
Clinical Features
Symptoms
Gradual onset unilateral scrotal pain (developing over hours to days — NOT sudden like torsion)
Scrotal swelling and erythema
Dysuria, urethral discharge (STI-related)
Fever and systemic illness
Urinary frequency/urgency (UTI-related)
Signs
Tender, swollen epididymis (initially posterior — may engulf entire testis)
Scrotal erythema and oedema
Positive Prehn sign (pain relieved on testicular elevation)
Cremasteric reflex present (unlike torsion where it is absent)
Normal testicular lie (unlike high-riding testis in torsion)
Urethral discharge (STI)
Reactive hydrocele
Investigations
First-line
Urinalysis and MSUPyuria supports infection. Culture identifies enteric organisms. May be normal in STI-related epididymitis
Urethral swab or first-void urine NAATTest for Chlamydia trachomatis and Neisseria gonorrhoeae (NAAT is highly sensitive)
FBC, CRPRaised WCC and CRP support infection
Second-line
Scrotal ultrasound with DopplerIf diagnostic uncertainty — shows increased blood flow to affected epididymis/testis (distinguishes from torsion which shows reduced flow). Also excludes abscess or underlying tumour
STI screenHIV, syphilis serology if STI-related — refer to GUM clinic for full screen and partner notification
1
STI-related (<35, sexually active)
- Ceftriaxone 500 mg IM stat (gonorrhoea cover) + doxycycline 100 mg BD for 10–14 days (chlamydia cover)
- If gonorrhoea excluded by NAAT: doxycycline alone may suffice
- GUM referral for full STI screen, partner notification, and contact tracing
- Abstain from sexual intercourse until treatment complete and partner treated
2
Non-STI-related (>35, enteric organisms)
- Ofloxacin 200 mg BD for 14 days (good prostatic/epididymal penetration)
- Or ciprofloxacin 500 mg BD for 10–14 days
- Investigate for underlying urological cause (USS KUB, flow rate, PSA) if recurrent
3
Supportive
- Scrotal elevation and support (tight underwear or jockstrap)
- Analgesia: NSAIDs (ibuprofen) + paracetamol
- Rest and ice packs
- If scrotal abscess develops: surgical drainage
Complications
- Abscess formation: Scrotal abscess requiring surgical drainage
- Chronic epididymitis: Persistent pain >3 months — may require epididymectomy in severe refractory cases
- Subfertility: Bilateral epididymitis (especially mumps) may cause obstructive azoospermia
- Missed torsion: Always consider torsion in the differential — if any doubt, explore surgically
UKMLA Exam Tips
- 1Key differentiator from torsion: GRADUAL onset (hours-days), dysuria, positive Prehn sign, cremasteric reflex PRESENT, normal testicular lie
- 2Age <35: STI (Chlamydia > Gonorrhoea). Age >35: enteric organisms (E. coli)
- 3If you cannot confidently distinguish from torsion → explore surgically. Never miss a torsion
- 4Mumps orchitis: unilateral in 80%, bilateral in 20%. Can cause subfertility — this is why MMR vaccination matters
- 5Fournier gangrene: necrotising fasciitis of perineum/scrotum — life-threatening complication. Surgical emergency (debridement + broad-spectrum IV antibiotics)
practicetest your knowledge on epididymo-orchitisApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — renal and beyond.
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