Acute inflammation of a testis along with its associated epididymis. Epididymo-orchitis causes severe pain and swelling at the back of the testis, and, in severe cases, swelling and redness of the scrotum.
The inflammation is caused by infection. Often, there is no obvious source of infection, but sometimes the cause is a bacterial urinary tract infection that has spread via the vas deferens to the epididymis. Treatment is with antibiotic drugs. If there is an underlying urinary tract infection, its cause will be investigated. (See also orchitis.)