Causes of Bilateral Orchitis
Bilateral orchitis is most commonly caused by mumps virus, with other viral etiologies including Coxsackie virus, rubella, Epstein-Barr virus, and varicella zoster virus, while bacterial causes typically result from extension of epididymitis due to gram-negative and gram-positive pathogens. 1
Viral Causes
Mumps virus remains the predominant viral cause of bilateral orchitis. The diagnosis is established through IgM serology for mumps antibodies or acute and convalescent IgG serology 1. Mumps can cause orchitis in up to 38% of postpubertal men who develop the infection, though bilateral involvement is less common than unilateral 2.
Other viral pathogens that can cause bilateral orchitis include:
- Coxsackie virus
- Rubella virus
- Epstein-Barr virus
- Varicella zoster virus (VZV) 1
These viral causes are diagnosed through appropriate serologic testing and typically present with systemic symptoms alongside testicular inflammation.
Bacterial Causes
Bacterial orchitis occurs predominantly through extension from contiguous epididymal infection and is caused by both gram-negative and gram-positive organisms 1. The age-based etiology differs significantly:
In Men <35 Years:
- Chlamydia trachomatis - most common sexually transmitted pathogen
- Neisseria gonorrhoeae - second most common STI cause
- These require NAAT testing for diagnosis 1
In Men >35 Years:
- Gram-negative enteric organisms (E. coli most common) - similar to UTI pathogens
- Gram-positive organisms
- Often associated with functional bladder outlet obstruction, benign prostatic hyperplasia, or urethral stricture 1, 3
Mycobacterial and Fungal Causes
Mycobacterium tuberculosis can involve both epididymis and testis, presenting as bilateral disease 1. This is particularly important in:
Systemic fungal infections that can cause bilateral involvement include:
- Blastomycosis
- Histoplasmosis
- Coccidioidomycosis 1
These require specific communication with the laboratory to ensure proper medium selection and processing for tissue cultures 1.
Special Clinical Scenarios
Post-vasectomy pain syndrome (PVPS) can present with bilateral testicular inflammation, though infection is rare in this setting 6.
Iatrogenic causes include bilateral tuberculous-like epididymo-orchitis occurring years after intravesical BCG therapy for bladder cancer 7.
Xanthogranulomatous orchitis represents a rare chronic inflammatory process that can be bilateral, particularly in patients with neuropathic bladder and recurrent UTIs 8.
Diagnostic Approach
For bacterial causes, obtain:
- Urinalysis and urine culture - first-line for men >35 years
- NAAT testing for CT/GC - essential for men <35 years or sexually active
- Gram stain of urethral exudate if urethritis present 1
For suspected viral causes:
- Serologic testing (IgM and IgG) for mumps and other viral pathogens 1
For mycobacterial/fungal causes:
- Tissue biopsy with appropriate cultures - requires advance laboratory notification 1
Critical Pitfall
The key clinical distinction is age-based: sexually transmitted pathogens dominate in younger men, while enteric organisms from urinary sources predominate in older men with structural urologic abnormalities 1, 3. However, gonococcal infection can occur even in octogenarians with multiple sexual partners, so sexual history remains essential regardless of age 9.