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Epididymo-orchitis

Last updated 22 Mar 2026 · STIs & Sexual Health

Aetiology and Assessment of Epididymo-orchitis

Microbiology and Pathophysiology

Epididymo-orchitis represents inflammation of the epididymis (epididymitis) with or without testicular involvement (orchitis). The condition predominantly affects sexually active men aged 14-35 years (sexually transmitted) and men over 35 years (urinary tract pathogen-related).

ℹ️
Australian Epidemiology: In Australia, approximately 600,000 cases of sexually transmitted infections occur annually, with epididymitis comprising 2-3% of presentations to emergency departments for scrotal pain in men aged 18-50 years.

Age-Stratified Aetiology

< 35 years
Sexually Transmitted
Primary: Chlamydia trachomatis (50-60%), Neisseria gonorrhoeae (10-15%)
Secondary: Mycoplasma genitalium, Ureaplasma spp.
Sexual Health Clinics, GP
≥ 35 years
Enteric Pathogens
Primary: E. coli (60-80%), Pseudomonas, Proteus
Associated: BPH, urinary retention, recent instrumentation
Emergency Departments, Urology
Any age
Special Circumstances
MSM: Enteric organisms (E. coli)
Post-procedural: Mixed flora
TB: Endemic areas, immunocompromised
Specialist referral indicated

Clinical Presentation

History

  • Onset: Gradual onset over days (vs. sudden onset in testicular torsion)
  • Pain: Unilateral scrotal pain, often radiating to ipsilateral lower abdomen
  • Urinary symptoms: Dysuria, frequency, urgency (more common in older men)
  • Sexual history: Recent new partner, unprotected intercourse, STI history
  • Discharge: Urethral discharge (suggests STI aetiology)
  • Fever: Low-grade fever, systemic upset
🚨
Red Flags: Sudden onset severe pain (consider torsion), high fever >38.5°C, vomiting, signs of sepsis, failure to respond to appropriate antibiotics within 48-72 hours.

Physical Examination

  • Inspection: Scrotal erythema, swelling, position of testis
  • Palpation: Tender, swollen epididymis (posterior-superior aspect of testis)
  • Cremasteric reflex: Usually preserved (absent in torsion)
  • Prehn's sign: Relief of pain with scrotal elevation (not reliable)
  • Urethral examination: Express urethral discharge if present
  • Abdominal examination: Assess for suprapubic tenderness, renal angle tenderness

Differential Diagnosis

Testicular Torsion
Sudden onset, high-riding testis, absent cremasteric reflex
Torsion of Appendix Testis
Young males, "blue dot sign", localised tenderness
Trauma
Clear history, scrotal haematoma
Testicular Tumour
Painless mass, age 15-35 years, firm consistency
Hydrocele/Varicocele
Transilluminates, positional component
Inguinal Hernia
Reducible mass, cough impulse

Diagnostic Criteria

Clinical diagnosis based on:

  1. Unilateral scrotal pain and swelling
  2. Tenderness localised to epididymis
  3. Gradual onset (>6 hours)
  4. Associated urinary symptoms or STI risk factors
  5. Exclusion of testicular torsion
⚠️
Clinical Pearl: In men under 35 years with suspected epididymitis, always consider STI aetiology and test accordingly. In men over 35 years, consider underlying urinary tract pathology.

Risk Factors

STI-Related (< 35 years)
  • Multiple sexual partners
  • New sexual partner
  • Unprotected intercourse
  • History of STIs
  • Partner with STI
  • Men who have sex with men (MSM)
Urinary Tract-Related (≥ 35 years)
  • Benign prostatic hyperplasia
  • Recent urinary catheterisation
  • Recent cystoscopy/TURP
  • Urinary tract abnormalities
  • Immunosuppression
  • Diabetes mellitus

Treatment of Epididymo-orchitis Suspected to be Caused by a Sexually Transmissible Pathogen

Clinical Approach

Epididymo-orchitis in sexually active men under 35 years is most commonly caused by sexually transmissible pathogens, particularly Chlamydia trachomatis and Neisseria gonorrhoeae. Empirical therapy should cover both organisms while awaiting microbiological results.

⚠️
Clinical Consideration: Always treat sexual partners within the preceding 60 days and provide STI counselling. Consider testing for other STIs including HIV, syphilis, and hepatitis B.

First-Line Empirical Therapy

💊
Doxycycline + Ceftriaxone
Vibramycin® + Rocephin® · Combination therapy
Adult Dose Doxycycline 100 mg + Ceftriaxone 500 mg
Route Oral + IM
Frequency Doxycycline twice daily + Ceftriaxone single dose
Duration Doxycycline 10 days + Ceftriaxone once
Renal Adj. None required
Hepatic Adj. Caution with doxycycline in severe impairment
PBS Status ✓ PBS General Benefit

Alternative First-Line Therapy

💊
Azithromycin + Ceftriaxone
Zithromax® + Rocephin® · Alternative combination
Adult Dose Azithromycin 1 g + Ceftriaxone 500 mg
Route Oral + IM
Frequency Both single doses
Duration Single day treatment
Renal Adj. None required
Hepatic Adj. Caution with azithromycin in severe impairment
PBS Status ✓ PBS General Benefit

Penicillin Allergy Alternatives

💊
Doxycycline + Spectinomycin
Vibramycin® + Trobicin® · Penicillin allergy option
Adult Dose Doxycycline 100 mg + Spectinomycin 2 g
Route Oral + IM
Frequency Doxycycline twice daily + Spectinomycin single dose
Duration Doxycycline 10 days + Spectinomycin once
Renal Adj. Spectinomycin dose reduction in severe impairment
Hepatic Adj. Caution with doxycycline
PBS Status ⚠️ PBS Authority Required

Severe Penicillin Allergy (Anaphylaxis History)

💊
Doxycycline + Azithromycin
Vibramycin® + Zithromax® · Severe allergy option
Adult Dose Doxycycline 100 mg + Azithromycin 1 g
Route Both oral
Frequency Doxycycline twice daily + Azithromycin single dose
Duration Doxycycline 10 days + Azithromycin once
Renal Adj. None required
Hepatic Adj. Caution with both drugs
PBS Status ✓ PBS General Benefit
ℹ️
Note: Consider specialist consultation for severe penicillin allergy cases or treatment failures. Fluoroquinolones are no longer recommended as first-line due to increasing resistance in N. gonorrhoeae.

Special Considerations for STI-related Epididymo-orchitis

  • Partner notification: All sexual partners within 60 days of symptom onset should be treated empirically
  • Abstinence: Avoid sexual contact until patient and partners complete treatment and are symptom-free
  • Test of cure: Not routinely required unless symptoms persist after appropriate treatment
  • Concurrent STI testing: Screen for syphilis, HIV, and hepatitis B
  • Gonorrhoea resistance: Consider culture and sensitivity if treatment failure occurs

Follow-up Requirements

48-72 hours
Clinical review if no improvement in pain or swelling
1 week
Routine follow-up to assess treatment response
2-4 weeks
Further review if symptoms persist; consider complications
3 months
STI re-screening as clinically indicated
🚨
Red Flags: Worsening pain, fever >38°C, signs of abscess formation, or failure to respond to appropriate therapy within 72 hours warrant urgent urological consultation.

Epididymo-orchitis suspected to be caused by a urinary tract pathogen

Clinical Context

Urinary tract pathogens are the predominant cause of epididymo-orchitis in men >35 years and younger men with risk factors for UTI (anatomical abnormalities, recent urological procedures, immunosuppression). The most common pathogens are E. coli, Enterococcus species, Klebsiella species, and Pseudomonas aeruginosa.

ℹ️
Australian Context: In remote and regional areas, delayed presentation may result in more severe infection requiring IV therapy. Consider patient access to follow-up when selecting treatment duration.

Risk Factors for UTI-Related Epididymo-orchitis

  • Age >35 years
  • Recent urological instrumentation or surgery
  • Structural urological abnormalities
  • Benign prostatic hyperplasia
  • Neurogenic bladder
  • Immunosuppression (diabetes, HIV, transplant recipients)
  • Recent catheterisation
  • Chronic prostatitis

Clinical Presentation

Mild
Uncomplicated
Unilateral scrotal pain and swelling, minimal systemic symptoms, able to walk normally
Outpatient management
Moderate
Complicated
Severe pain, difficulty walking, fever, nausea, but hemodynamically stable
Consider admission
Severe
Complicated with sepsis
Systemic toxicity, sepsis, inability to tolerate oral therapy, concern for abscess
Hospital admission required

Investigations

  • Essential
    Mid-stream urine (MSU)
    Collect before antibiotic therapy. Send for microscopy, culture and antimicrobial susceptibility testing (AST).
  • Essential
    Urine dipstick
    May show nitrites, leucocyte esterase, protein. Normal dipstick does not exclude UTI in men.
  • Available
    Blood cultures
    If fever >38°C or systemically unwell. Available at all public hospitals.
  • Available
    Full blood count
    May show leucocytosis. Available at all pathology laboratories.
  • Available
    C-reactive protein
    Elevated in bacterial infection. Available at all pathology laboratories.
  • Specialist
    Scrotal ultrasound
    If concern for testicular torsion, abscess formation, or poor response to therapy. Available at major hospitals and imaging centres.
⚠️
Important: First-catch urine should be avoided as it may contain urethral contaminants. MSU is preferred for men with suspected UTI-related epididymo-orchitis.

Empirical Antimicrobial Therapy

First-line Therapy (Oral - Outpatient)

💊
Trimethoprim-sulfamethoxazole
Bactrim® · Septrin® · First-line
Adult Dose 160/800 mg (1 DS tablet)
Route Oral
Frequency Twice daily
Duration 14 days
Renal Adj. CrCl 15-30: 50% dose; CrCl <15: avoid
Hepatic Adj. Caution in severe impairment
PBS Status ✓ PBS General Benefit

Second-line Therapy (Oral)

💊
Ciprofloxacin
Ciproxin® · Cipro® · Second-line
Adult Dose 500 mg
Route Oral
Frequency Twice daily
Duration 14 days
Renal Adj. CrCl 30-60: 250-500 mg BD; CrCl <30: 250 mg BD
Hepatic Adj. No adjustment required
PBS Status ✓ PBS General Benefit
⚠️
Fluoroquinolone Resistance: Australian surveillance data shows increasing fluoroquinolone resistance in E. coli (15-25% in some regions). Consider local antimicrobial resistance patterns and previous antibiotic exposure.

Severe Infection - Intravenous Therapy

💉
Ceftriaxone
Rocephin® · Broad-spectrum
Adult Dose 1 g
Route IV
Frequency Once daily
Duration Until clinically improved, then switch to oral
Renal Adj. No adjustment if CrCl >10
Hepatic Adj. Monitor in severe impairment
PBS Status R Restricted Benefit

Beta-lactam Allergy Alternatives

💊
Gentamicin
Garamycin® · Allergy alternative
Adult Dose 5-7 mg/kg
Route IV
Frequency Once daily
Duration Maximum 5-7 days
Renal Adj. Reduce dose and extend interval based on levels
Hepatic Adj. No adjustment required
PBS Status ✓ PBS General Benefit
⚠️
Gentamicin Monitoring: Mandatory monitoring of serum levels, renal function, and hearing (particularly important in elderly

References

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    Trojian TH, Lishnak TS, Heiman D. Epididymitis and orchitis: an overview. American Family Physician. 2009;79(7):583-587.
  • 02
    Centers for Disease Control and Prevention. Sexually transmitted infections treatment guidelines, 2021: epididymitis. MMWR Recommendations and Reports. 2021;70(4):1-187.
  • 03
    Pilatz A, Hossain H, Kaiser R, et al. Acute epididymitis revisited: impact of molecular diagnostics on etiology and contemporary guideline recommendations. European Urology. 2015;68(3):428-435. doi:10.1016/j.eururo.2015.01.012
  • 04
    Australian Sexual Health Alliance. Australian STI Management Guidelines for use in primary care. Sydney: ASHA; 2022. Available from: www.sti.guidelines.org.au
  • 05
    Nickel JC, Teichman JM, Gregoire M, et al. Prevalence, diagnosis, characterization, and treatment of prostatitis, interstitial cystitis, and epididymitis in outpatient urological practice. Urology. 2005;66(4):753-760. doi:10.1016/j.urology.2005.04.031
  • 06
    Royal Australian College of General Practitioners. Guidelines for preventive activities in general practice. 9th ed. Melbourne: RACGP; 2016.
  • 07
    Department of Health and Aged Care. National notifiable diseases surveillance system annual report 2022. Canberra: Australian Government; 2023.
  • 08
    Wammen K, Samuelsson S, Jakobsson L, et al. Acute epididymitis in a population-based cohort: clinical characteristics and antimicrobial treatment. Scandinavian Journal of Urology. 2019;53(6):382-387. doi:10.1080/21681805.2019.1665048
  • 09
    Australian Institute of Health and Welfare. Aboriginal and Torres Strait Islander Health Performance Framework 2020: online data tables. Canberra: AIHW; 2020. Cat. no. IHW 247.
  • 10
    PBS Online. Pharmaceutical Benefits Scheme: general schedule. Canberra: Department of Health and Aged Care; 2024. Available from: www.pbs.gov.au
  • 11
    Australian Commission on Safety and Quality in Health Care. NSQHS Standards. 2nd ed. Sydney: ACSQHC; 2017.
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    Bébéar C, de Barbeyrac B. Genital Chlamydia trachomatis infections. Clinical Microbiology and Infection. 2009;15(1):4-10. doi:10.1111/j.1469-0691.2008.02647.x
  • 13
    McMillan A, Pakianathan MR, Mao JH, et al. Urogenital chlamydial infection in men with urethritis and their female partners. British Journal of Venereal Diseases. 1983;59(2):106-109.
  • 14
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    Kong FY, Tabrizi SN, Fairley CK, et al. The efficacy of azithromycin and doxycycline for the treatment of rectal chlamydia infection: a systematic review and meta-analysis. Journal of Antimicrobial Chemotherapy. 2015;70(5):1290-1297. doi:10.1093/jac/dku574