Causes

Orchitis can be caused by a bacterial or viral infection. Sometimes a cause of orchitis can't be determined.

Bacterial orchitis

Most often, bacterial orchitis is associated with or the result of epididymitis. Epididymitis usually is caused by an infection of the urethra or bladder that spreads to the epididymis.

Often, the cause of the infection is an STI. Other causes of infection can be related to having been born with abnormalities in your urinary tract or having had a catheter or medical instruments inserted into your penis.

Viral orchitis

The mumps virus usually causes viral orchitis. Nearly one-third of males who contract the mumps after puberty develop orchitis, usually four to seven days after onset of the mumps.