Overview

Orchitis (or-KIE-tis) is an inflammation of one or both testicles. Bacterial or viral infections can cause orchitis, or the cause can be unknown. Orchitis is most often the result of a bacterial infection, such as a sexually transmitted infection (STI). In some cases, the mumps virus can cause orchitis.

Bacterial orchitis might be associated with epididymitis — an inflammation of the coiled tube (epididymis) at the back of the testicle that stores and carries sperm. In that case, it's called epididymo-orchitis.

Orchitis causes pain and can affect fertility. Medication can treat the causes of bacterial orchitis and can ease some signs and symptoms of viral orchitis. But it can take several weeks for scrotal tenderness to disappear.