Summary

Epididymo-orchitis is an acute inflammatory condition affecting the epididymis and/or testis, most commonly caused by bacterial infection. In sexually active men under 35, the predominant pathogens are sexually transmitted organisms (Chlamydia trachomatis and Neisseria gonorrhoeae). In men over 35 and those with urological abnormalities, coliform bacteria (E. coli) from urinary tract infections are the usual cause. Patients present with unilateral scrotal pain, swelling, and tenderness, often with urinary symptoms. The critical differential diagnosis is testicular torsion, which requires urgent surgical exploration. Treatment depends on the likely organism: ceftriaxone plus doxycycline for STI-related cases, and fluoroquinolones for enteric organisms.

Key Facts

• Definition: Inflammation of epididymis ± testis, usually bacterial
• Incidence: Most common cause of acute scrotal pain in adults
• Age distribution: Under 35 years — usually STI; over 35 years — usually enteric organisms
• Key organisms (under 35): Chlamydia trachomatis, Neisseria gonorrhoeae
• Key organisms (over 35): E. coli, Enterococcus, Pseudomonas
• Critical DDx: Testicular torsion (emergency — time-sensitive)
• Prehn's sign: Pain relieved by elevating testis (suggests epididymitis, NOT torsion)

Clinical Pearls

"Under 35 = STI, Over 35 = UTI": This age-based rule guides empirical antibiotic choice. Under 35s need STI cover (ceftriaxone + doxycycline); over 35s need enteric cover (fluoroquinolone).

Prehn's Sign Is Unreliable: Although classically taught, Prehn's sign (pain relief on elevation) is NOT reliable enough to exclude testicular torsion. If in doubt, get an ultrasound or surgical opinion.

Think Torsion First in Young Patients: In adolescents and young adults with acute scrotal pain, testicular torsion must be excluded BEFORE diagnosing epididymitis. Misdiagnosis delays surgery and risks testicular loss.

Why This Matters Clinically

Epididymo-orchitis is common but the key clinical challenge is distinguishing it from testicular torsion, which requires emergency surgery within 6 hours to save the testis. STI-related cases require partner notification and testing. Untreated or inadequately treated epididymo-orchitis can lead to abscess formation, infertility, and chronic pain.

Structured Approach

General:

• Vital signs (fever, tachycardia)
• Signs of sepsis

Scrotal Examination:

• Inspect: Swelling, erythema, skin changes
• Palpate: Locate tenderness (epididymis vs testis), assess testicular position
• Assess cremasteric reflex

Urethral Examination:

• Inspect for discharge
• Take swabs if discharge present

Abdominal/DRE (if indicated):

• Exclude pelvic mass
• Assess prostate (if UTI suspected)

Special Tests

Natural History

• Untreated: May develop abscess, chronic pain, or rarely spread to Fournier's gangrene
• With treatment: Most resolve within 1-2 weeks

Outcomes with Treatment

Prognostic Factors

Good Prognosis:

• Young, otherwise healthy patient
• Prompt treatment
• Unilateral involvement
• No abscess formation

Poor Prognosis:

• Delayed presentation
• Abscess at presentation
• Underlying urological abnormality not corrected
• Immunocompromised
• Recurrent episodes

Key Guidelines

1. BASHH (British Association for Sexual Health and HIV) Guidelines (2020) — Epididymo-orchitis management. Recommends ceftriaxone + doxycycline for STI-related. BASHH
2. EAU (European Association of Urology) Guidelines on Urological Infections — Comprehensive guidance. EAU
3. CDC STI Treatment Guidelines (2021) — Updated antibiotic recommendations. CDC

Landmark Studies

Berger et al. (1979) — Classic study on aetiology

• Established age-based organism distribution (STI vs enteric)
• Key finding: Chlamydia and Gonorrhoea predominant in under 35s
• Clinical Impact: Foundation for age-based empirical therapy

Tracy et al. (2016) — Systematic review

• Reviewed antibiotic efficacy for epididymitis
• Key finding: Fluoroquinolones effective for enteric organisms; ceftriaxone + doxycycline for STI
• Clinical Impact: Confirmed current treatment recommendations

Evidence Strength

What is Epididymo-orchitis?

Epididymo-orchitis is an infection causing pain and swelling in one (or rarely both) of the testicles. The infection usually starts in the tubes behind the testicle (the epididymis) and can spread to the testicle itself. In younger men (under 35), it's often caused by sexually transmitted infections like chlamydia. In older men, it's usually caused by bacteria from a urine infection.

Is it serious?

Most cases are not serious and get better with antibiotics. However, it's very important that the doctor rules out a condition called testicular torsion, where the testicle twists and loses its blood supply — this is an emergency. That's why anyone with sudden testicle pain should see a doctor urgently.

How is it treated?

1. Antibiotics: Depending on your age and likely cause, you'll get antibiotics for 1-2 weeks. Take the full course even if you feel better.
2. Pain relief: Anti-inflammatory tablets (like ibuprofen) and paracetamol help with pain and swelling.
3. Supportive underwear: Wearing snug underwear or a jockstrap can provide comfort.
4. Rest: Avoid strenuous activity until symptoms improve.
5. Partner testing: If it's an STI, your sexual partner(s) should also be tested and treated.

What to expect

• Swelling and pain usually start to improve within 3-5 days of antibiotics
• Full resolution may take 2-4 weeks
• Some mild discomfort may persist for several weeks
• A follow-up may be arranged to ensure complete resolution

When to seek help

See a doctor urgently if:

• You have sudden, severe testicle pain (could be torsion)
• Your symptoms are getting worse despite antibiotics
• You develop a high fever or feel very unwell
• The scrotum becomes red or starts to look abnormal (black, weeping)
• You notice a lump that doesn't go away after the infection clears