Swelling called inflammation that affects one or both testicles.

Orchitis causes include infections with viruses or with germs called bacteria. For instance, germs that lead to sexually transmitted infections can cause orchitis. So can the mumps virus. Sometimes, the cause isn't known.

Orchitis symptoms often start suddenly. They can include swelling in one or both testicles, pain that ranges from mild to serious, fever, upset stomach and vomiting, and a general sense of not feeling well.

Orchitis treatment includes medicine to clear up an infection caused by germs. Medicine also can ease some symptoms of orchitis that is caused by viruses. Bed rest and the use of cold packs may help too.