Particularly among
men over age 35
in whom the cause is E. coli, epididymitis is commonly due to
urinary tract obstruction.[2] Less common microbes include Ureaplasma, Mycobacterium, and cytomegalovirus, or Cryptococcus in patients with HIV infection. E. coli is more common in boys before puberty, the elderly and homosexual men.
Non-infectious causes are also possible. Reflux of sterile urine (urine without bacteria) through the ejaculatory ducts may cause inflammation with obstruction.