What causes epididymitis in the absence of a sexually transmitted infection (STI)?

Causes of Non-STI Epididymitis

In the absence of sexually transmitted infections, epididymitis is most commonly caused by urinary tract infections with gram-negative enteric organisms, particularly in men over 35 years of age, those with recent urinary tract instrumentation or surgery, and those with anatomical abnormalities of the urinary tract. 1

Age-Related Causes

Men Under 35 Years

While STIs (particularly Chlamydia trachomatis and Neisseria gonorrhoeae) are the predominant cause in this age group, non-STI causes include:

• Reflux of urine into ejaculatory ducts (particularly in children under 14) 2
• Enteric bacteria in men who practice insertive anal intercourse 1
• Anatomical abnormalities of the urinary tract 1

Men Over 35 Years

• Gram-negative enteric organisms (particularly E. coli - responsible for 56% of cases) 3
• Reflux of urine into ejaculatory ducts secondary to bladder outlet obstruction 1, 2
• Benign prostatic hyperplasia causing functional bladder outlet problems 4
• Urethral stricture disease 4

Other Non-STI Causes

• Recent urinary tract instrumentation or surgery 1
• Anatomical abnormalities of the urinary tract 1
• Systemic infections (uncommon) 5
• Trauma (uncommon) 5
• Viral infections (rare - found in only 1% of cases) 3

Diagnostic Approach for Non-STI Epididymitis

1. Clinical presentation: Gradual onset of posterior scrotal pain, possibly with urinary symptoms (dysuria, frequency)
2. Physical examination: Swollen and tender epididymis with testis in normal anatomical position 2
3. Key diagnostic tests:
   • Urinalysis and urine culture for enteric organisms
   • Examination of first-void urine for leukocytes
   • Abdominal examination for palpable bladder
   • Digital rectal examination to check for BPH, prostate cancer, and prostatitis 6

Treatment Considerations

For epididymitis most likely caused by enteric organisms (non-STI) in men over 35 years:

• Fluoroquinolones (ofloxacin 300 mg orally twice daily for 10 days or levofloxacin 500 mg orally once daily for 10 days) 1
• Consider alternative antibiotics due to rising fluoroquinolone resistance in E. coli 4

Important Differential Diagnoses

Always rule out testicular torsion, especially in younger patients with:

• Sudden onset of pain (vs. gradual in epididymitis)
• No relief with scrotal elevation
• Absent cremasteric reflex
• High-riding testis
• Decreased/absent blood flow on Doppler ultrasound 1

Complications of Untreated Epididymitis

• Infertility
• Chronic scrotal pain
• Abscess formation
• Testicular ischemia 2

Early diagnosis and appropriate treatment are essential to prevent these complications and reduce patient morbidity.