Particularly among men
over age 35 in
whom the cause is E. coli, epididymitis is commonly due to urinary tract
obstruction. 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.