Epididymo-orchitis

Inflammation of the epididymis (epididymitis) and/or testis (orchitis), most often infective. Always exclude testicular torsion first in any acute scrotal pain presentation — torsion can destroy the testis within hours and cannot be safely excluded by history/examination alone.

Causative organisms

Group	Likely organisms
Sexually active men < 35 years	Chlamydia trachomatis, occasionally Neisseria gonorrhoeae
Sexually active men of any age	As above — but insertive anal sex or recent urinary tract instrumentation raises the likelihood of enteric pathogens (E. coli, Proteus spp)
Men > 35 years / non-sexually acquired	Coliform bacteria (E. coli) more likely, often following catheterisation/instrumentation
Children	Enteroviruses, adenoviruses, mumps, E. coli
Chronic infection	Mycobacterium tuberculosis; any of the above if inadequately treated
Immunocompromised	CMV, Cryptococcus, Pseudomonas aeruginosa, Klebsiella pneumoniae
Non-infectious	Amiodarone, sarcoidosis, Behçet’s disease, polyarteritis nodosa, idiopathic
Rare	Brucellosis, syphilis, filariasis, Ureaplasma urealyticum

Paramyxovirus (mumps) should be considered at any age.

Clinical features

• Scrotal pain and swelling — swelling, induration and tenderness of the epididymis is the most common sign, usually unilateral. Onset is typically over hours to days (unlike the sudden onset of torsion). Consider testicular cancer if swelling is confined to the body of the testis without tenderness.
• Erythema/oedema may or may not be visible; lymphadenopathy may be present.
• Dysuria or urethral discharge — but urethral symptoms are often absent despite an STI being present, so their absence doesn’t exclude a sexually acquired cause.
• Suprapubic pain, frequency, and nocturia suggest a urinary pathogen rather than an STI.
• If very acute in onset or severe, treat as torsion until proven otherwise and refer emergently.

Investigations

• First-void urine for gonorrhoea/chlamydia NAAT (PCR).
• MSU for urinary pathogens.
• If urethral discharge is present, take a sample for gonorrhoea culture and sensitivity before starting empirical antibiotics.
• Doppler ultrasonography can help exclude testicular infarction, torsion, or tumour — but don’t let a normal scan override strong clinical suspicion of torsion.

Management

Bed rest, scrotal support, and analgesia are commonly needed. Substantial improvement should occur within 4–5 days; complete resolution of swelling may take several weeks.

Sexually acquired

Treat sexually active men presumptively for gonorrhoea and chlamydia:

• Ceftriaxone 500mg in 2mL of 1% lignocaine IMI, stat, plus either
• Doxycycline 100mg PO BD for 14 days, or
• Azithromycin 1g PO stat, repeated 1 week later.

Severe cases may need treatment continued up to 3 weeks. All sexual partners from the past 6 months should be tested and treated. Arrange test of cure for gonorrhoea at 2 weeks, and retest for chlamydia/gonorrhoea at 3 months.

Non-sexually acquired

Adults, 14 days of one of:

• First line: trimethoprim 300mg daily.
• Second line: cefalexin 500mg BD.
• Third line: amoxycillin+clavulanate 500+125mg BD, or nitrofurantoin 100mg BD.
• If resistant to the above: ciprofloxacin 500mg BD or norfloxacin 400mg BD for 2 weeks — always check sensitivities and de-escalate/adjust once known.

Children, 14 days of one of:

• First line: trimethoprim+sulfamethoxazole (4+20mg/kg up to 160+800mg BD), or trimethoprim 4mg/kg up to 150mg BD (if a liquid formulation is available).
• Second line: cephalexin 12.5mg/kg up to 500mg QID.
• Third line: amoxicillin+clavulanate 22.5+3.2mg/kg up to 875+125mg BD.
• In prepubertal boys, ~80% of cases are viral — if urinalysis is negative for leucocytes/nitrites, it’s reasonable to withhold antibiotics and manage symptomatically.

If fevers or systemic sepsis are present, refer to ED for IV therapy (e.g. ampicillin + gentamicin, or ceftriaxone if gentamicin is contraindicated).

Review post-treatment to confirm resolution and arrange renal tract imaging; if not resolving, arrange testicular ultrasound before referring to urology.

Referral

Refer to the Emergency Department for urgent urological review if diagnosis is uncertain and pain is severe (torsion can destroy the testis within hours), or if severe infection needs IV antibiotics.

Sexually acquired infection — refer to a specialist sexual health clinic if symptoms persist despite adherence, contact-tracing support is needed, or gonorrhoea test of cure at 2 weeks is positive.

Non-sexually acquired infection — refer to urology if symptoms haven’t settled within 30 days of starting antibiotics (arrange testicular ultrasound first), or if urinary tract imaging shows an abnormality.

Follow-up

Contact tracing is needed for any STI found in a sexually active man. Check whether a female partner may be pregnant. Children found to have an STI need further investigation (safeguarding).