Epididymitis is an acute inflammation of the epididymis which can cause severe scrotal pain. It is important to differentiate epididymitis from testicular torsion or testicular appendage torsion.


  • Epididymitis is the most common cause of acute scrotum, approximately 37–65% of cases. The incidence ranges between 0.8 and 1.2 cases per 1,000 persons per year.
  • There is a bimodal distribution with a peak in incidence in infants <1 year of age and peripubertal boys.

Risk Factors

Urologic manipulation (cystoscopy, intermittent self-catheterization, surgery of the urethra)


  • The majority of epididymitis is idiopathic (73%).
  • Viral epididymitis: second most common cause
    • Urinalysis and culture are negative.
    • Often elevated titers of enterovirus, Mycoplasma pneumoniae, and adenoviruses.
    • New research suggests that some epididymitis might be due to postinfectious inflammation as 50% of patients had respiratory symptoms within 1 month of presentation, and presentations appear to peak in concert with rotavirus and enterovirus.
  • Bacterial epididymitis: 2–6% of cases and is related to age
    • Due to ascending infection from the urethra or bladder, reflux of infected urine into the vas deferens, or hematogenous dissemination
    • Infants <1 year:
      • Typically due to genitourinary anomalies (73% vs. 21% in children >1)
      • Abnormalities include meatal stenosis, neurogenic voiding dysfunction, urethral stenosis, posterior urethral valves, ectopic ureter.
      • Typical bacteria include Escherichia coli, Klebsiella, and Enterococcus.
      • Postpubertal sexually active boys may have infection with sexually transmitted diseases such as gonorrhea or chlamydia.
  • Chemical epididymitis: due to reflux of sterile urine into the vas deferens or drugs (amiodarone)
  • Posttraumatic

Commonly Associated Conditions

  • Systemic serositis (familial Mediterranean fever, sarcoidosis, Kawasaki disease)
  • Systemic vasculitis (Henoch-Schönlein purpura, polyarteritis nodosa)

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