When one or both testicles are swollen, it is often distressing and can cause a great deal of discomfort. For someone who is sexually active, it is easy to assume that swollen testicles are the result of an STD; however, there are many infectious and noninfectious causes of testicular swelling.

Infectious causes of swollen testicles include Testicular Cancer, Epididymitis (inflammation of the tube that carries sperm from the testicle to the penis) caused by the sexually transmitted diseases chlamydia or gonorrhea. These STDs can cause a range of other symptoms besides swollen testicles, and are easily treated with antibiotics. Orchitis (inflammation of one or both of the testicles) can also be caused by several types of bacteria and some viruses (including the virus that causes mumps).

Swollen testicles, or a sensation of a fullness in the testicle, can also be caused by an inguinal hernia. Inguinal hernias occur when part of the intestine becomes displaced, slipping through the inguinal canal into the testis. This creates a noticeable bulge in the testicular sac, swelling, and sometimes pain as the intestinal loop is confined in such a small space.标题加粗  Severe causes of testicular swelling
Testicular masses, such as a hydrocele, spermatocele, or (rarely) testicular cancer are also causes of testicular swelling. A hydrocele (fluid collection around the testicle), spermatocele (cyst that forms in the epididymis), and testicular cancer can all be painless, but can cause pain when they become large enough to press on other structures in the groin.

Because testicular swelling can be caused by some potentially serious processes, it's important that anyone experiencing testicular swelling be evaluated by a physician to determine the cause. Swelling accompanied by sudden, severe testicle pain requires immediate medical care. You should seek immediate care if:

Your testicular swelling is accompanied by severe or sudden pain, nausea, or vomiting
You feel a lump in the scrotum
Your swelling is accompanied by fever
Your scrotum is tender to the touch, is red, or feels warm
You have been in recent contact with someone who has mumps (virus that can cause orchitis)