Aetiology and Assessment of Epididymo-orchitis
Epidemiology and Risk Factors
Epididymo-orchitis is one of the most common urological conditions in Australia, with an annual incidence of approximately 600 cases per 100,000 men aged 18-50 years. The condition shows a bimodal age distribution: sexually transmitted infections (STIs) predominate in men under 35 years, while bacterial causes are more common in older men with urological abnormalities.
Australian Context: Rates of chlamydial epididymitis are particularly high in remote Aboriginal and Torres Strait Islander communities, with incidence rates 3-5 times higher than non-Indigenous populations.
Key Risk Factors
- Sexual activity (STI-related causes in men <35 years)
- Urological abnormalities (BPH, urethral stricture, neurogenic bladder)
- Recent urological instrumentation or catheterisation
- Immunosuppression
- Chronic indwelling catheters
- Recent heavy lifting or straining (sterile inflammatory epididymitis)
Aetiology
STI-Related Epididymitis (<35 years)
- Chlamydia trachomatis (60-70% of cases)
- Neisseria gonorrhoeae (15-20% of cases)
- Co-infection common (10-15%)
- Mycoplasma genitalium (emerging pathogen)
- Ureaplasma urealyticum
Bacterial Epididymitis (≥35 years)
- Escherichia coli (most common)
- Enterococcus faecalis
- Pseudomonas aeruginosa
- Klebsiella pneumoniae
- MRSA (healthcare-associated cases)
Antimicrobial Resistance: In Australia, increasing rates of fluoroquinolone-resistant E. coli (25-30%) and extended-spectrum β-lactamase (ESBL) producers (8-12%) affect empirical therapy choices.
Special Aetiological Considerations
- Viral orchitis: Mumps (rare due to MMR vaccination), EBV, CMV in immunocompromised
- Tuberculous epididymitis: Consider in high-risk populations, immigrants from endemic areas
- Fungal causes: Candida species in immunocompromised or diabetic patients
- Sterile inflammatory: Post-vasectomy, medication-induced (amiodarone)
Clinical Assessment
History
- Onset and duration of symptoms (acute vs chronic)
- Pain severity and radiation patterns
- Urethral discharge or dysuria
- Sexual history including new partners, condom use
- Recent urological procedures or instrumentation
- Previous episodes of epididymitis
- Immunosuppression or chronic illness
- Medication history (quinolones, amiodarone)
Physical Examination
1
General Assessment
Vital signs, fever, general appearance, lymphadenopathy
2
Genitourinary Examination
Inspect external genitalia, urethral meatus for discharge
3
Scrotal Examination
Palpate testis and epididymis, assess cremasteric reflex, transillumination
4
Abdominal Examination
Assess for suprapubic tenderness, costovertebral angle tenderness
Red Flags: High fever (>38.5°C), severe systemic symptoms, absent cremasteric reflex, horizontal testicular lie, or nausea/vomiting may indicate testicular torsion requiring emergency urological consultation.
Clinical Signs
Mild
Epididymitis
• Unilateral scrotal pain and swelling
• Tender, swollen epididymis
• Preserved testicular position
• Positive Prehn's sign
• Normal cremasteric reflex
• Tender, swollen epididymis
• Preserved testicular position
• Positive Prehn's sign
• Normal cremasteric reflex
Outpatient management
Moderate
Epididymo-orchitis
• Epididymal and testicular involvement
• Scrotal erythema and oedema
• Fever (<38.5°C)
• Urethral discharge
• Reactive hydrocele
• Scrotal erythema and oedema
• Fever (<38.5°C)
• Urethral discharge
• Reactive hydrocele
Outpatient with close follow-up
Severe
Complicated Disease
• High fever (>38.5°C)
• Systemic toxicity
• Scrotal cellulitis
• Suspected abscess
• Failed outpatient therapy
• Systemic toxicity
• Scrotal cellulitis
• Suspected abscess
• Failed outpatient therapy
Hospital admission required
Diagnostic Criteria
Diagnosis is primarily clinical, supported by appropriate investigations. The presence of unilateral scrotal pain and swelling with a tender, enlarged epididymis in the appropriate clinical context establishes the diagnosis.
| Clinical Feature | Epididymitis | Testicular Torsion | Torsion of Appendix Testis |
|---|---|---|---|
| Onset | Gradual (hours to days) | Sudden (minutes to hours) | Gradual |
| Age | Any age | Bimodal (neonates, adolescents) | Prepubertal boys |
| Fever | Often present | Usually absent | Low-grade or absent |
| Prehn's sign | Positive (pain relief) | Negative | Variable |
| Cremasteric reflex | Present | Absent | Present |
| Testicular position | Normal | High-riding, horizontal | Normal |
Prehn's Sign
Elevation of the affected testis provides pain relief in epididymitis but typically worsens pain in testicular torsion. However, this sign is not completely reliable and should not be the sole basis for diagnosis.
Clinical Pearl: When clinical distinction between epididymitis and testicular torsion is unclear, urgent scrotal Doppler ultrasound is indicated. If ultrasound is not immediately available and torsion cannot be excluded, emergency urological consultation is required.
Treatment of epididymo-orchitis suspected to be caused by a sexually transmissible pathogen
First-line Empirical Therapy
For men <35 years or those with high risk of sexually transmitted infection (STI), empirical therapy should cover Chlamydia trachomatis and Neisseria gonorrhoeae.
Doxycycline + Ceftriaxone
Preferred combination
Doxycycline Adult
100 mg
Ceftriaxone Adult
500 mg
Route
Doxy: Oral, Ceftriaxone: IM
Frequency
Doxy: BD, Ceftriaxone: Single dose
Duration
Doxycycline: 10 days
Renal Adj.
None for either drug
PBS Status
✓ PBS General Benefit
Alternative First-line Options
Azithromycin + Ceftriaxone
Alternative combination
Azithromycin Adult
1 g
Ceftriaxone Adult
500 mg
Route
Azith: Oral, Ceftriaxone: IM
Frequency
Both: Single dose
Duration
Single dose therapy
Renal Adj.
None required
PBS Status
✓ PBS General Benefit
Gonococcal Resistance: Increasing ceftriaxone resistance reported in Australia. Consider spectinomycin 2 g IM if ceftriaxone resistance suspected.
Penicillin Allergy Alternatives
Doxycycline + Spectinomycin
Penicillin allergy option
Doxycycline Adult
100 mg
Spectinomycin Adult
2 g
Route
Doxy: Oral, Spectinomycin: IM
Frequency
Doxy: BD, Spectinomycin: Single dose
Duration
Doxycycline: 10 days
Renal Adj.
Spectinomycin: reduce dose in severe renal impairment
PBS Status
PBS Authority Required
Azithromycin + Ciprofloxacin
Alternative for penicillin allergy
Azithromycin Adult
1 g stat, then 500 mg daily
Ciprofloxacin Adult
500 mg
Route
Both: Oral
Frequency
Azith: Daily, Cipro: BD
Duration
Both: 10 days total
Renal Adj.
Ciprofloxacin: reduce dose if CrCl <30 mL/min
PBS Status
✓ PBS General Benefit
Fluoroquinolone Resistance: High rates of quinolone-resistant gonorrhoea in Australia (>30%). Avoid ciprofloxacin monotherapy for gonorrhoea treatment.
Directed Therapy Based on Pathogen
Chlamydia trachomatis
Doxycycline
Vibramycin® · First-line
Adult Dose
100 mg
Route
Oral
Frequency
Twice daily
Duration
10 days
PBS Status
✓ PBS General Benefit
Neisseria gonorrhoeae
Ceftriaxone
Rocephin® · First-line
Adult Dose
500 mg
Route
Intramuscular
Frequency
Single dose
Duration
One dose only
PBS Status
✓ PBS General Benefit
Special Considerations
Partner Management
Contact Tracing
All sexual partners within 60 days should be tested and treated
Notification
Gonorrhoea and chlamydia are notifiable conditions in all Australian jurisdictions
Follow-up
Test of Cure
Recommended 2-4 weeks post-treatment for gonorrhoea
Re-testing
Repeat testing at 3 months recommended due to high re-infection rates
Clinical Response: Symptoms should improve within 48-72 hours of appropriate therapy. Lack of response suggests treatment failure, non-adherence, or alternative diagnosis.
Epididymo-orchitis suspected to be caused by a urinary tract pathogen
Clinical Context: This category applies to men >35 years, those with recent urological procedures, indwelling catheters, or anatomical abnormalities of the genitourinary tract.
Clinical Indicators
Epididymo-orchitis is suspected to be caused by a urinary tract pathogen when:
- Patient age >35 years
- Recent urological instrumentation or surgery
- Indwelling urethral or suprapubic catheter
- Known urological anatomical abnormalities
- History of recurrent UTIs
- Concurrent urinary symptoms (dysuria, frequency, urgency)
- Abnormal urinalysis suggestive of UTI
- Recent hospitalisation or healthcare exposure
Common Urinary Tract Pathogens
Organism
Frequency
Risk Factors
Notes
E. coli
40-60%
Most common, elderly
ESBL prevalence ~10-15% in Australia
Klebsiella pneumoniae
10-15%
Healthcare exposure, DM
Rising ESBL rates
Enterococcus spp.
10-15%
Instrumentation, elderly
VRE rare in community
Pseudomonas aeruginosa
5-10%
Structural abnormalities, recurrent UTI
Intrinsic resistance to many antibiotics
Proteus mirabilis
5-8%
Stones, alkaline urine
Urease producer
Empirical Antimicrobial Therapy
First-line Therapy
Trimethoprim-sulfamethoxazole
Bactrim® · Co-trimoxazole · Oral first-line
Adult Dose
160/800 mg
Route
Oral
Frequency
Twice daily
Duration
10-14 days
Renal Adj.
Avoid if CrCl <15 mL/min
PBS Status
✓ PBS General Benefit
Cephalexin
Keflex® · First-generation cephalosporin
Adult Dose
500 mg
Route
Oral
Frequency
Four times daily
Duration
10-14 days
Renal Adj.
Reduce dose if CrCl <50 mL/min
PBS Status
✓ PBS General Benefit
Second-line Therapy
Ciprofloxacin
Ciproxin® · Fluoroquinolone
Adult Dose
500 mg
Route
Oral
Frequency
Twice daily
Duration
10-14 days
Renal Adj.
Reduce dose if CrCl <30 mL/min
PBS Status
⚡ PBS Restricted Benefit
Amoxycillin-clavulanate
Augmentin® · β-lactam/β-lactamase inhibitor
Adult Dose
875/125 mg
Route
Oral
Frequency
Twice daily
Duration
10-14 days
Renal Adj.
Reduce dose if CrCl <30 mL/min
PBS Status
✓ PBS General Benefit
Severe Disease or Hospitalisation
Ceftriaxone
Rocephin® · Third-generation cephalosporin
Adult Dose
1-2 g
Route
IV
Frequency
Once daily
Duration
Until clinically stable, then oral
Renal Adj.
None required
PBS Status
✓ PBS General Benefit
Gentamicin
Garamycin® · Aminoglycoside
Adult Dose
5-7 mg/kg
Route
IV
Frequency
Once daily
Duration
3-5 days maximum
Renal Adj.
Dose reduction required
PBS Status
✓ PBS General Benefit
Gentamicin Monitoring: Requires therapeutic drug monitoring with pre-dose levels. Avoid in elderly or renal impairment unless no alternatives.
Penicillin Allergy Alternatives
References
-
01
Trojian TH, Lishnak TS, Heiman D. Epididymitis and orchitis: an overview. Am Fam Physician. 2009;79(7):583-587.
-
02
Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187. doi:10.15585/mmwr.rr7004a1
-
03
Nickel JC. Chronic epididymitis: a practical approach to understanding and managing a difficult urologic enigma. Rev Urol. 2003;5(4):209-215.
-
04
Australian Commission on Safety and Quality in Health Care. Antimicrobial Stewardship Clinical Care Standard. Sydney: ACSQHC; 2020. Available at: https://www.safetyandquality.gov.au/standards/clinical-care-standards/antimicrobial-stewardship-clinical-care-standard
-
05
Department of Health, Australian Government. National Male Health Policy 2010. Canberra: Commonwealth of Australia; 2010. Available at: https://www.health.gov.au/resources/publications/national-male-health-policy
-
06
Luzzi GA, O'Brien TS. Acute epididymitis. BJU Int. 2001;87(8):747-755. doi:10.1046/j.1464-410x.2001.02189.x
-
07
Pilatz A, Hossain H, Kaiser R, et al. Acute epididymitis revisited: impact of molecular diagnostics on etiology and contemporary guideline recommendations. Eur Urol. 2015;68(3):428-435. doi:10.1016/j.eururo.2014.12.005
-
08
Australian Institute of Health and Welfare. The Health of Australia's Males: Exploring the Factors that Shape Men's Health Outcomes. Canberra: AIHW; 2019. Report no.: PHE 239.
-
09
Pharmaceutical Benefits Scheme. PBS Online. Canberra: Australian Government Department of Health; 2024. Available at: https://www.pbs.gov.au/pbs/home
-
10
Royal Australian College of General Practitioners. Management of sexually transmissible infections in Aboriginal and Torres Strait Islander populations: Australian STI management guidelines for use in primary care. East Melbourne: RACGP; 2018.
-
11
Bowie WR, Alexander ER, Holmes KK. Etiologies of acute urethritis in men. Sex Transm Dis. 1977;4(3):99-104.
-
12
McConaghy JR, Panchal B. Epididymitis: an overview. Am Fam Physician. 2016;94(9):723-726.
-
13
Australian Indigenous HealthInfoNet. Overview of Indigenous male health. Perth: Australian Indigenous HealthInfoNet; 2023. Available at: https://healthinfonet.ecu.edu.au/learn/health-topics/mens-health/
-
14
Naber KG, Roscher K, Botto H, Schaefer V. Oral levofloxacin versus ciprofloxacin for treatment of chronic bacterial prostatitis. J Antimicrob Chemother. 2008;62(3):537-544. doi:10.1093/jac/dkn224
-
15
Communicable Diseases Intelligence. National Notifiable Diseases Surveillance System. Australian Government Department of Health; 2023. Available at: https://nindss.health.gov.au/
Epididymo-orchitis suspected to be caused by a urinary tract pathogen
Clinical Context: This category applies to men >35 years, those with recent urological procedures, indwelling catheters, or anatomical abnormalities of the genitourinary tract.
Clinical Indicators
Epididymo-orchitis is suspected to be caused by a urinary tract pathogen when:
- Patient age >35 years
- Recent urological instrumentation or surgery
- Indwelling urethral or suprapubic catheter
- Known urological anatomical abnormalities
- History of recurrent UTIs
- Concurrent urinary symptoms (dysuria, frequency, urgency)
- Abnormal urinalysis suggestive of UTI
- Recent hospitalisation or healthcare exposure
Common Urinary Tract Pathogens
| Organism | Frequency | Risk Factors | Notes |
|---|---|---|---|
| E. coli | 40-60% | Most common, elderly | ESBL prevalence ~10-15% in Australia |
| Klebsiella pneumoniae | 10-15% | Healthcare exposure, DM | Rising ESBL rates |
| Enterococcus spp. | 10-15% | Instrumentation, elderly | VRE rare in community |
| Pseudomonas aeruginosa | 5-10% | Structural abnormalities, recurrent UTI | Intrinsic resistance to many antibiotics |
| Proteus mirabilis | 5-8% | Stones, alkaline urine | Urease producer |
Empirical Antimicrobial Therapy
First-line Therapy
Trimethoprim-sulfamethoxazole
Bactrim® · Co-trimoxazole · Oral first-line
Adult Dose
160/800 mg
Route
Oral
Frequency
Twice daily
Duration
10-14 days
Renal Adj.
Avoid if CrCl <15 mL/min
PBS Status
✓ PBS General Benefit
Cephalexin
Keflex® · First-generation cephalosporin
Adult Dose
500 mg
Route
Oral
Frequency
Four times daily
Duration
10-14 days
Renal Adj.
Reduce dose if CrCl <50 mL/min
PBS Status
✓ PBS General Benefit
Second-line Therapy
Ciprofloxacin
Ciproxin® · Fluoroquinolone
Adult Dose
500 mg
Route
Oral
Frequency
Twice daily
Duration
10-14 days
Renal Adj.
Reduce dose if CrCl <30 mL/min
PBS Status
⚡ PBS Restricted Benefit
Amoxycillin-clavulanate
Augmentin® · β-lactam/β-lactamase inhibitor
Adult Dose
875/125 mg
Route
Oral
Frequency
Twice daily
Duration
10-14 days
Renal Adj.
Reduce dose if CrCl <30 mL/min
PBS Status
✓ PBS General Benefit
Severe Disease or Hospitalisation
Ceftriaxone
Rocephin® · Third-generation cephalosporin
Adult Dose
1-2 g
Route
IV
Frequency
Once daily
Duration
Until clinically stable, then oral
Renal Adj.
None required
PBS Status
✓ PBS General Benefit
Gentamicin
Garamycin® · Aminoglycoside
Adult Dose
5-7 mg/kg
Route
IV
Frequency
Once daily
Duration
3-5 days maximum
Renal Adj.
Dose reduction required
PBS Status
✓ PBS General Benefit
Gentamicin Monitoring: Requires therapeutic drug monitoring with pre-dose levels. Avoid in elderly or renal impairment unless no alternatives.
Penicillin Allergy Alternatives
References
-
01
Trojian TH, Lishnak TS, Heiman D. Epididymitis and orchitis: an overview. Am Fam Physician. 2009;79(7):583-587.
-
02
Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187. doi:10.15585/mmwr.rr7004a1
-
03
Nickel JC. Chronic epididymitis: a practical approach to understanding and managing a difficult urologic enigma. Rev Urol. 2003;5(4):209-215.
-
04
Australian Commission on Safety and Quality in Health Care. Antimicrobial Stewardship Clinical Care Standard. Sydney: ACSQHC; 2020. Available at: https://www.safetyandquality.gov.au/standards/clinical-care-standards/antimicrobial-stewardship-clinical-care-standard
-
05
Department of Health, Australian Government. National Male Health Policy 2010. Canberra: Commonwealth of Australia; 2010. Available at: https://www.health.gov.au/resources/publications/national-male-health-policy
-
06
Luzzi GA, O'Brien TS. Acute epididymitis. BJU Int. 2001;87(8):747-755. doi:10.1046/j.1464-410x.2001.02189.x
-
07
Pilatz A, Hossain H, Kaiser R, et al. Acute epididymitis revisited: impact of molecular diagnostics on etiology and contemporary guideline recommendations. Eur Urol. 2015;68(3):428-435. doi:10.1016/j.eururo.2014.12.005
-
08
Australian Institute of Health and Welfare. The Health of Australia's Males: Exploring the Factors that Shape Men's Health Outcomes. Canberra: AIHW; 2019. Report no.: PHE 239.
-
09
Pharmaceutical Benefits Scheme. PBS Online. Canberra: Australian Government Department of Health; 2024. Available at: https://www.pbs.gov.au/pbs/home
-
10
Royal Australian College of General Practitioners. Management of sexually transmissible infections in Aboriginal and Torres Strait Islander populations: Australian STI management guidelines for use in primary care. East Melbourne: RACGP; 2018.
-
11
Bowie WR, Alexander ER, Holmes KK. Etiologies of acute urethritis in men. Sex Transm Dis. 1977;4(3):99-104.
-
12
McConaghy JR, Panchal B. Epididymitis: an overview. Am Fam Physician. 2016;94(9):723-726.
-
13
Australian Indigenous HealthInfoNet. Overview of Indigenous male health. Perth: Australian Indigenous HealthInfoNet; 2023. Available at: https://healthinfonet.ecu.edu.au/learn/health-topics/mens-health/
-
14
Naber KG, Roscher K, Botto H, Schaefer V. Oral levofloxacin versus ciprofloxacin for treatment of chronic bacterial prostatitis. J Antimicrob Chemother. 2008;62(3):537-544. doi:10.1093/jac/dkn224
-
15
Communicable Diseases Intelligence. National Notifiable Diseases Surveillance System. Australian Government Department of Health; 2023. Available at: https://nindss.health.gov.au/