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Epididymo-Orchitis

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Overview

Epididymitis is the inflammation of the epididymis, the tubular structure at the posterior testis responsible for the storage, maturation, and transport of sperm cells. Orchitis is the inflammation of the testis.

Epididymo-orchitis is the inflammation of both the epididymis and testis. Over 50% of people with epididymitis also have orchitis. Isolated orchitis is much less common. Its most common cause is infection spreading from the urethra or bladder.

Causes

Overview

Epidemiological data shows the following causes are the most common:

  • <35 years old and sexually active: sexually transmitted infections (STIs) are the most common cause (Chlamydia trachomatis and Neisseria gonorrhoeae)
  • >35 years old with a low-risk sexual history: enteric organisms that cause urinary tract infections (UTIs) are more common (Escherichia coli)

This is a general assumption and in reality, more detail would be needed through a thorough sexual history.

Other rare causes include:

  • Mumps (in up to 40% of post-pubertal males, rare in pre-pubertal males)
  • Extrapulmonary tuberculosis
  • Non-infective causes: Behçet’s disease and vasculitis

Epidemiology

  • In people <35 years old who are sexually active, STIs are the more likely cause
    • In people >35 years old with a low-risk sexual history, enteric organisms are more likely
  • Incidence is highest in people aged 15-35 years old and people >60 years.

Presentation

Overview

  • Acute unilateral scrotal pain and/or swelling – usually over days
  • Urethral discharge and/or dysuria may be present if an STI is the cause
  • There may be a recent history of UTI
  • Fever
  • Palpating the epididymis may reveal tenderness
  • Positive Prehn’s sign – lifting the affected testis alleviates pain

The key differential diagnosis is testicular torsion, which can present similarly but requires immediate hospital admission for surgery.

Differential Diagnoses

Testicular torsion

  • Pain and swelling usually develop over a few days unlike testicular torsion, which is often sudden
  • Dysuria and increased urgency may be seen in epididymo-orchitis but not in testicular torsion
  • Prehn’s sign is positive in epididymo-orchitis but negative in testicular torsion
  • The cremasteric reflex is present in epididymo-orchitis but absent in testicular torsion

Investigations

Overview

If symptoms are severe, the patient is systemically unwell, or there is suspicion of a complication, arrange hospital admission.

For patients that do not need hospital admission, investigations are based on age and risk factors:

  • Younger people (<35 years old) and sexually active:
    • Assess for STI (e.g. nucleic acid amplification testing, NAAT)
  • >35 years old and low-risk sexual history:
    • Send a mid-stream urine sample for microscopy and culture

Management

Overview

  • If an STI is the suspected cause:
    • Urgently refer to sexual health clinic
    • If the organism is unknown: IM single dose ceftriaxone, and oral doxycycline for 10-14 days
  • If an enteric organism is the suspected cause:
    • Send a mid-stream urine sample if not already done
    • Give oral quinolone for 2 weeks (e.g. ofloxacin)

Complications

  • Sepsis
  • Abscess formation and testicular ischaemia/infarction
  • Reactive hydrocele
  • Testicular atrophy and subfertility/infertility (particularly mumps orchitis)
  • Chronic scrotal pain

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