Epididymoorchitis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Dima Nimri, M.D. [2]


Epididymoorchitis refers to the inflammation of the epididymis and/or testes, with or without infection. While the pathogenesis is not fully understood, infectious epididymoorchitis is thought to be due to retrograde reflux of infected urine into the epididymis, which then spreads to the testes.[1][2]



Epididymoorchitis refers to the inflammation of the epididymis and/or testes, with or without infection. While the pathogenesis is not fully understood, the following are the proposed mechanisms behind epididymoorchitis:[1][2]

  • The retrograde ascent of infectious pathogens is the usual route of infection. Most cases of epididymoorchitis start with inflammation of the epididymis (i.e., epididymitis), which then spread to the adjacent testicle (i.e., orchitis). Because orchitis tends to occur in patients with concurrent epididymitis, cases are mostly referred to as epididymoorchitis.
  • Isolated cases of orchitis are usually due to mumps virus and in isolated cases of orchitis, blood-borne dissemination is the usual route of infection.
  • Retrograde flow of infected urine into the ejaculatory duct is thought to cause epididymoorchitis.
  • For infectious cases of epididymoorchitis that are not associated with an STD or UTI, it is believed that these cases may be related a post-infectious inflammatory reaction. When taking viral cultures of throat, stool and urine, it was found that patients with epididymoorchitis had elevated titers to certain pathogens, as compared to controls. Most notably, patients with epididymoorchitis had elevated titers to M. pneumonia and adenovirus.
  • The mechanism behind non-infectious epididymoorchitis remains unclear.

Gross Pathology

Microscopic Pathology

Acute epididymoorchitis is characterized by infiltration of neutrophils. Chronic cases of epididymoorchitis, such as in sarcoidosis or tuberculosis, are characterized by granulomatous inflammation.

Associated Conditions

The following conditions may be associated with epididymoorchitis:[1]


  1. 1.0 1.1 1.2 Trojian TH, Lishnak TS, Heiman D (2009). "Epididymitis and orchitis: an overview". Am Fam Physician. 79 (7): 583–7. PMID 19378875.
  2. 2.0 2.1 2.2 Tracy CR, Steers WD, Costabile R (2008). "Diagnosis and management of epididymitis". Urol. Clin. North Am. 35 (1): 101–8, vii. doi:10.1016/j.ucl.2007.09.013. PMID 18061028.