Non-Bacterial Causes of Epididymo-Orchitis
The primary non-bacterial causes of epididymo-orchitis include viral infections (most notably mumps virus), fungal pathogens (Candida species, Blastomyces, Histoplasma, Coccidioides), and Mycobacterium tuberculosis. 1
Viral Etiologies
Mumps virus is the most frequent cause of viral orchitis, typically causing blood-borne dissemination to the testis rather than ascending infection. 1, 2 The diagnosis is established through IgM serology for mumps antibodies or by demonstrating a rise in IgG titers between acute and convalescent samples. 1
Additional viral pathogens that can cause epididymo-orchitis include:
These viral infections characteristically spread hematogenously rather than through retrograde ascent from the urinary tract. 2
Fungal Infections
Candidal epididymo-orchitis occurs in patients with recognized risk factors for fungal infection, particularly after urinary tract instrumentation. 3 Both Candida albicans and Candida glabrata have been documented as causative organisms. 3
Systemic fungal diseases that can involve the epididymis or testis include:
Candidal epididymo-orchitis often requires drainage or orchidectomy for definitive diagnosis and treatment, though oral antifungals alone have been effective in select cases. 3
Mycobacterial Disease
Mycobacterium tuberculosis can involve the epididymis and testis, typically through hematogenous spread as part of systemic dissemination. 1 This diagnosis requires specific communication with the laboratory to ensure proper medium selection and processing, particularly when tissue specimens are obtained surgically. 1
Clinical Context and Diagnostic Approach
When persistent swelling and tenderness remain after completing antimicrobial therapy for presumed bacterial epididymo-orchitis, the differential diagnosis must include tumor, abscess, infarction, testicular cancer, tuberculous epididymitis, and fungal epididymitis. 1, 4
Immunosuppressed and HIV-infected patients warrant heightened suspicion for fungal and mycobacterial causes, though they should initially receive the same empiric bacterial treatment regimens as immunocompetent patients. 4, 5
Key Diagnostic Pitfalls
Laboratory diagnosis of fungal and mycobacterial epididymo-orchitis requires explicit communication from the clinician to the laboratory to ensure appropriate medium selection and processing protocols are implemented. 1 Without this communication, these pathogens may be missed entirely.
Viral orchitis predominantly affects the testis through hematogenous spread rather than the epididymis through retrograde infection, distinguishing it mechanistically from bacterial causes. 2 This explains why isolated orchitis without epididymal involvement should raise suspicion for viral or other blood-borne etiologies.