Orchitis is inflammation of the testis, most commonly viral (mumps) in isolated orchitis or bacterial when occurring as epididymo-orchitis. Isolated orchitis without epididymitis is uncommon in adults except in the setting of mumps. [1] Men aged 14–35 are most frequently affected, with Chlamydia trachomatis and Neisseria gonorrhoeae as the predominant pathogens in this age group; enteric organisms (e.g., E. coli) predominate in men >35 years. [1-2]
The following figure provides a useful algorithmic approach to evaluating scrotal masses, including painful presentations such as orchitis:
1. History
- Onset and progression: Gradual onset of unilateral scrotal pain over hours to days (contrast with sudden onset in torsion) [2][4]
- Symptom characterization: Dull aching scrotal pain, heaviness, swelling; may radiate to inguinal region or lower abdomen
- Associated symptoms: Dysuria, urinary frequency, urethral discharge, fever, chills, nausea [2-3]
- Sexual history: Number of partners, condom use, insertive anal intercourse, recent new partner, history of STIs [5]
- Viral prodrome: Parotid swelling 4–8 days prior (mumps orchitis); fever, malaise, headache [6]
- Important negatives: Absence of sudden onset, absence of nausea/vomiting at onset (helps exclude torsion); no trauma history [4]
- Urologic history: Prior instrumentation, catheterization, prostate biopsy, vasectomy, BPH [5]
2. Alarm Features
- Sudden-onset severe unilateral scrotal pain → must rule out testicular torsion (surgical emergency; salvage rate ~90% within 6 hours, drops to 50% at 12 hours) [3]
- Absent cremasteric reflex (OR 47.6 for torsion) [3]
- High-riding or transversely oriented testis [3-4]
- Nausea/vomiting with acute onset [4][7]
- Signs of scrotal abscess or Fournier's gangrene: crepitus, necrotic skin, rapidly spreading erythema, hemodynamic instability [5]
- Failure to improve within 48–72 hours of antibiotics → consider abscess, infarction, resistant organism, or alternative diagnosis [1]
- Testicular necrosis can occur even when inflammatory markers improve — serial Doppler monitoring is critical in high-risk patients [8]
3. Medications
- Empiric antibiotic regimens[3][5]
- Ceftriaxone dose: Use 1 g for patients ≥150 kg; the 2024 European guideline now recommends 1 g for all patients [5][9]
- Azithromycin dual therapy is no longer recommended unless cefixime is used as an alternative to ceftriaxone [9]
- Mumps orchitis: Supportive care only (no antivirals); analgesics and anti-inflammatories [6]
- Adjunctive therapy: NSAIDs, scrotal elevation, bed rest until fever and inflammation subside [3][5]
- Medication contributors: Amiodarone can cause a sterile epididymitis/orchitis (dose-dependent; consider dose reduction or discontinuation) [3]
4. Diet
- No specific dietary triggers for orchitis
- Adequate hydration is important, particularly if febrile or on fluoroquinolones (reduce crystalluria risk)
- Encourage anti-inflammatory diet (fruits, vegetables, omega-3 fatty acids) for general recovery support
5. Review of Systems
- GU: Dysuria, frequency, urgency, hematuria, urethral discharge, testicular pain/swelling
- Constitutional: Fever, chills, malaise, weight loss
- ENT/Salivary: Parotid swelling, jaw pain (mumps) [6]
- Neurologic: Headache, neck stiffness (mumps meningitis complication) [6]
- GI: Nausea, vomiting, abdominal pain (may be sole presenting symptom of torsion in children) [7]
- MSK: Arthralgias (mumps-associated)
- Dermatologic: Scrotal skin changes, rash (Fournier's, herpes)
6. Collateral History and Family History
- Sexual contacts: Partners should be notified and treated if STI confirmed; evaluate partners from the prior 60 days [3]
- Vaccination history: MMR vaccination status — incomplete or absent vaccination increases mumps orchitis risk [10-11]
- Family history: History of testicular torsion (bell-clapper deformity may be familial) [3]
- Exposure history: Contact with known mumps cases, recent outbreaks (university settings, close-knit communities) [11]
- Travel/occupational history: Endemic fungal infections (blastomycosis, coccidioidomycosis, histoplasmosis) or TB exposure in appropriate settings [1]
7. Risk Factors
- Sexually transmitted orchitis/epididymo-orchitis: Multiple sexual partners, unprotected intercourse, MSM (insertive anal sex), age 14–35 [1-2][5]
- Enteric organism-related: Age >35, BPH, bladder outlet obstruction, urethral stricture, recent urologic instrumentation, prostate biopsy, indwelling catheter [5][12]
- Mumps orchitis: Unvaccinated or incompletely vaccinated postpubertal males; outbreaks in universities and close-knit communities [10-11]
- Other risk factors: Amiodarone use, prolonged sitting, bicycle riding, trauma, urogenital abnormalities, immunosuppression [3][5]
8. Differential Diagnosis
- Testicular torsion — sudden onset, absent cremasteric reflex, high-riding testis; cannot-miss surgical emergency [3-4]
- Torsion of testicular appendage — gradual superior pole pain, "blue dot sign," normal blood flow on Doppler [3]
- Epididymitis (without orchitis) — tenderness localized to epididymis, more common than isolated orchitis [2-3]
- Testicular tumor — painless mass (painful in ~15% of cases); firm, non-transilluminating intratesticular mass [13]
- Incarcerated/strangulated inguinal hernia — reducible mass, bowel sounds in scrotum, obstructive symptoms [14]
- Fournier's gangrene — rapidly progressive scrotal erythema, crepitus, systemic toxicity [15-16]
- Testicular infarction (segmental) — focal pain, wedge-shaped avascular area on Doppler [16]
- Hydrocele (reactive) — may accompany orchitis; painless transilluminating fluid collection [13]
- Trauma — history of injury, hematocele, possible testicular rupture [16]
9. Past Medical History
- Prior episodes of orchitis or epididymitis (recurrence rate ~14%) [17]
- History of STIs
- BPH, urethral stricture, or other urologic conditions [5]
- Prior urologic surgery or instrumentation [5]
- Immunosuppression (HIV, diabetes, transplant) [5]
- Cryptorchidism or prior orchidopexy [18]
- Childhood mumps or MMR vaccination status [10]
10. Physical Exam
- Vital signs: Fever (often present in bacterial orchitis; high fever common in mumps orchitis) [2][6]
- Scrotal inspection: Unilateral (or bilateral) swelling, erythema, warmth; scrotal wall thickening
- Palpation: Tender, enlarged testis in normal anatomic position (not high-riding); epididymal tenderness if epididymo-orchitis [2]
- Cremasteric reflex: Intact in orchitis/epididymitis (absent in torsion — critical distinguishing feature) [2][4]
- Prehn sign: Pain relief with scrotal elevation may occur in orchitis (insufficient sensitivity to rule out torsion) [3]
- Urethral discharge: Suggests STI etiology
- Blue dot sign: Pathognomonic for torsion of testicular appendage (not orchitis) [3]
- Inguinal exam: Lymphadenopathy, hernia assessment
- Parotid glands: Bilateral swelling suggests mumps [6]
- Abdominal exam: Rule out referred pain, peritonitis
11. Lab Studies
12. Imaging
- First-line: Scrotal ultrasound with color Doppler — the established first-line imaging modality for the acute scrotum per ACR Appropriateness Criteria [15][20]
- Orchitis/epididymo-orchitis: Enlarged, hypoechoic testis/epididymis with increased blood flow on Doppler (sensitivity ~100% for detecting inflammation) [14][20]
- Reactive hydrocele and scrotal wall thickening commonly seen [20]
- Critical role: Differentiates orchitis (increased flow) from torsion (decreased/absent flow) [14][20]
- Serial Doppler monitoring recommended in high-risk patients (elderly, diabetic, immunocompromised) to detect progression to ischemia or abscess [8]
- Contrast-enhanced US or MRI: Problem-solving tools when standard US is equivocal [16]
- Imaging is unnecessary when clinical presentation is classic and low suspicion for torsion, though most ED presentations warrant US to exclude torsion
13. Special Tests
- TWIST Score (Testicular Workup for Ischemia and Suspected Torsion): Validated clinical prediction tool to stratify torsion risk — score of 0–1 has ~1% torsion risk; score of 7 has ~100% torsion risk [3-4]
- Point-of-care ultrasound (POCUS): ED-performed testicular US has 95% sensitivity and 94% specificity compared with radiology US [15]
- NAAT testing for GC/CT is the most sensitive diagnostic method for STI-related orchitis [1]
- Mumps RT-PCR from buccal swab or urine for suspected mumps orchitis [1]
14. ECG
- Not routinely indicated for orchitis
- Obtain ECG if amiodarone-induced orchitis is suspected (patient will already be on cardiac monitoring)
- Consider ECG if patient is febrile and tachycardic to evaluate for myocarditis (rare mumps complication)
15. Assessment
Bacterial epididymo-orchitis is the most common presentation in adults, typically with gradual onset of unilateral scrotal pain, swelling, fever, and urinary symptoms. Isolated orchitis without epididymitis is uncommon except in mumps, which presents 4–8 days after parotitis with abrupt testicular swelling and high fever. [1][6]
Severity stratification
- Mild: Low-grade fever, moderate swelling, tolerating PO, no abscess → outpatient management
- Moderate-severe: High fever, significant swelling, diabetes, elevated CRP, abscess on imaging → consider hospitalization [5]
Complications
- Testicular abscess (correlates with need for orchiectomy, p = 0.035) [17]
- Testicular atrophy (up to 50% of mumps orchitis cases show some degree of reduced testicular size) [6][21]
- Infertility: Spermatogram abnormalities in ~25% after mumps orchitis, though true sterility is rare even after bilateral orchitis [6]
- Chronic orchitis/pain [5][22]
- Testicular necrosis (rare but reported) [8]
- Overall, ~5% of patients with acute epididymo-orchitis experience testicular loss or atrophy [17]
16. Treatment Plan
Initial stabilization
- Analgesics: NSAIDs (ibuprofen 400–600 mg PO q6–8h) ± acetaminophen
- Scrotal elevation and ice packs
- Bed rest until fever and local inflammation subside [3][5]
Empiric antibiotics (start at time of visit, before lab results): [5]
- STI suspected: Ceftriaxone 500 mg IM × 1 + Doxycycline 100 mg PO BID × 10 days
- STI + enteric risk: Ceftriaxone 500 mg IM × 1 + Levofloxacin 500 mg PO daily × 10 days
- Enteric only: Levofloxacin 500 mg PO daily × 10 days
Mumps orchitis: Supportive care only — analgesics, scrotal support, ice; interferon-alpha has been studied but is not standard of care [6]
Partner notification: If STI confirmed, treat sexual partners from the prior 60 days; patient should abstain from intercourse until treatment is completed and symptoms resolve [3][19]
Abscess: Surgical drainage or orchiectomy if necrotic [8][17]
17. Disposition
- Discharge (majority of cases): Able to tolerate PO antibiotics, no signs of systemic toxicity, reliable follow-up, torsion excluded [5]
- Admission criteria: [5]
- Severe pain or high fever suggesting alternative diagnosis (torsion, infarction, abscess, Fournier's)
- Inability to tolerate oral medications
- Testicular abscess on imaging
- Immunocompromised, diabetic, or elderly with systemic illness
- Elevated CRP with systemic signs
- Diagnostic uncertainty (cannot exclude torsion)
- Urology consultation:
- Suspected torsion or abscess
- Failure to improve at 48–72 hours [1]
- Recurrent epididymo-orchitis (evaluate for structural abnormalities) [1]
- Pre-pubertal orchitis (evaluate for genitourinary anomalies) [1]
18. Follow Up / Return Precautions
- Follow-up in 48–72 hours to assess clinical response; if no improvement, pursue additional diagnostic testing and consider alternative diagnoses or resistant organisms [1]
- Repeat imaging if worsening symptoms despite appropriate antibiotics (rule out abscess, infarction) [8]
- Test of cure: Repeat NAAT for GC/CT is not routinely needed if symptoms resolve, but retest in 3 months for reinfection screening [19]
- Return precautions — instruct patient to return immediately for:
- Worsening or sudden increase in pain
- New-onset nausea/vomiting
- Fever not improving after 48 hours of antibiotics
- Scrotal skin changes (discoloration, crepitus)
- Inability to tolerate oral medications
- Expected recovery: Swelling and discomfort may take several weeks to fully resolve even after completing antibiotics [5]
- Long-term: Counsel regarding potential for testicular atrophy and fertility implications, particularly after mumps orchitis (sterility is rare even after bilateral involvement); consider semen analysis if fertility concerns arise after recovery [6][18]
References
1. Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2024 Update by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM). — Miller JM, Binnicker MJ, Campbell S, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
2. Epididymitis and Orchitis: An Overview. — Trojian TH, Lishnak TS, Heiman D. American Family Physician. 2009.
3. Scrotal Masses. — Langan RC, Puente MEE. American Family Physician. 2022.
4. Clinical Diagnosis of Testicular Torsion. — Ebell MH. American Family Physician. 2022.
5. Sexually Transmitted Infections Treatment Guidelines, 2021. — Workowski KA, Bachmann LH, Chan PA, et al. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2021.
6. Mumps. — Hviid A, Rubin S, Mühlemann K. Lancet. 2008.
7. What Parents and Teens Need to Know About Testicular Pain. — Angulo MI, Collazo GR, Thompson LA. JAMA Pediatrics. 2025.
8. Acute Epididymo-Orchitis Complicated by Outcomes of Either Testicular Necrosis or Complete Recovery: Two Case Reports. — Cao B, Zhang C, Xiao F, Wu Y, Ouyang Q. Medicine. 2025.
9. The 2024 European Guideline on the Management of Epididymo-Orchitis. — Justice ED, Fricker J, Ross JDC, et al. Journal of the European Academy of Dermatology and Venereology : JEADV. 2025.
10. Prevention of Measles, Rubella, Congenital Rubella Syndrome, and Mumps, 2013: Summary Recommendations of the Advisory Committee on Immunization Practices (ACIP). — Huong Q. McLean, Amy Parker Fiebelkorn, Jonathan L. Temte, Gregory S. Wallace Advisory Committee on Immunization Practices. 2013.
11. Recommendation of the Advisory Committee on Immunization Practices for Use of a Third Dose of Mumps Virus-Containing Vaccine in Persons at Increased Risk for Mumps During an Outbreak. — Marin M, Marlow M, Moore KL, Patel M. MMWR. Morbidity and Mortality Weekly Report. 2018.
12. Epididymo-Orchitis Caused by Enteric Organisms in Men > 35 years Old: Beyond Fluoroquinolones. — Ryan L, Daly P, Cullen I, Doyle M. European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology. 2018.
13. Evaluation of Scrotal Masses. — Crawford P, Crop JA. American Family Physician. 2014.
14. Differential Diagnosis of Acute Scrotum in Childhood And Adolescence With High-Resolution Duplex Sonography. — Deeg KH. Ultraschall in Der Medizin. 2021.
15. Ultrasound Guidelines: Emergency, Point-of-Care, and Clinical Ultrasound Guidelines in Medicine. — American College of Emergency Physicians (2023). 2023.
16. Imaging of the Acute Scrotum: Keys to a Rapid Diagnosis of Acute Scrotal Disorders. — Sweet DE, Feldman MK, Remer EM. Abdominal Radiology. 2020.
17. Outcome of Acute Epididymo-Orchitis: Risk Factors for Testicular Loss. — Norton SM, Saies A, Browne E, et al. World Journal of Urology. 2023.
18. Male Infertility. — Agarwal A, Baskaran S, Parekh N, et al. Lancet. 2021.
19. Sexually Transmitted Infections: Updated Guideline From the CDC. — Klein DA, Valerio CR, Cofield ZN. American Family Physician. 2022.
20. ACR Appropriateness Criteria® Acute Onset of Scrotal Pain-Without Trauma, Without Antecedent Mass: 2024 Update. — Expert Panel on Urological Imaging, Gerena M, Allen BC, et al. Journal of the American College of Radiology : JACR. 2024.
21. Male Hypogonadism. — Basaria S. Lancet. 2014.
22. Chronic Orchitis: A Neglected Cause of Male Infertility?. — Schuppe HC, Meinhardt A, Allam JP, et al. Andrologia. 2008.