What causes epididymitis?

Causes of Epididymitis

Epididymitis is most commonly caused by sexually transmitted infections (STIs) in men under 35 years of age, particularly Neisseria gonorrhoeae and Chlamydia trachomatis, while in older men it is typically caused by enteric bacteria associated with urinary tract abnormalities. 1

Age-Related Causative Pathogens

Men Under 35 Years

• Sexually Transmitted Infections (STIs):
  • Chlamydia trachomatis (most common STI cause) 1, 2, 3
  • Neisseria gonorrhoeae 1, 2
• In men who are insertive partners during anal intercourse:
  • Enteric organisms (particularly E. coli) 1, 2

Men Over 35 Years

• Enteric bacteria (primarily E. coli, followed by Streptococcus, Klebsiella, Pseudomonas, and Serratia) 1, 3
• These infections are often associated with:
  • Functional bladder outlet problems
  • Benign prostatic hyperplasia
  • Urethral stricture disease
  • Recent urinary tract instrumentation or surgery 1, 4

Children (Under 14 Years)

• The etiology is largely unknown, but reflux of urine into the ejaculatory ducts is considered the most common cause 2

Pathophysiology

The main routes of infection include:

1. Retrograde propagation through the vas deferens (most common) 5
2. Blood-borne dissemination (less common, primarily in orchitis) 6

Risk Factors

• Sexual activity (particularly in young adults) 1, 2
• Unprotected intercourse (condoms provide 80-90% protection against STI transmission when used correctly) 1
• Urinary tract abnormalities (particularly in men >35 years) 1, 4
  • Bladder outlet obstruction
  • Prostatic hyperplasia
  • Urethral strictures
• Recent urological procedures or catheterization 1

Clinical Presentation

Epididymitis typically presents with:

• Gradual onset of posterior scrotal pain
• Swollen and tender epididymis
• Testis in anatomically normal position
• May be accompanied by urinary symptoms (dysuria, frequency) 2
• Pain relief with testicular elevation (positive Prehn sign) 1
• Present cremasteric reflex (distinguishing it from testicular torsion) 1

Diagnostic Considerations

A proper diagnostic evaluation should include:

• Urethral swab or first-void urine for STI testing
• Urinalysis and urine culture
• Scrotal ultrasound with Doppler (to rule out torsion) 1

Treatment Implications

The causative organism guides treatment approach:

• For STI-related epididymitis: Ceftriaxone 250 mg IM single dose PLUS Doxycycline 100 mg orally twice daily for 10-14 days 1, 7
• For enteric organism-related epididymitis: Fluoroquinolones (though rising resistance is a concern) 4

Important Clinical Pitfalls

1. Failure to test for STIs: Only about 50% of men diagnosed with epididymitis are tested for gonorrhea and chlamydia 3

2. Misdiagnosis of testicular torsion: Epididymitis must be distinguished from testicular torsion, which requires immediate surgical intervention. Key differences include:

   • Epididymitis: Gradual onset, positive Prehn sign, present cremasteric reflex
   • Torsion: Sudden onset, negative Prehn sign, absent cremasteric reflex, high-riding testicle 1

3. Neglecting partner treatment: Sexual partners of patients with STI-related epididymitis should be referred for evaluation and treatment to prevent reinfection 1

4. Inappropriate antibiotic selection: Treatment should be tailored to the likely causative organism based on patient age and risk factors 1, 2