Testicular swelling, also known as testicular hydrocele, is a common medical condition where one or both of the testicles become enlarged and swollen. This condition is often caused by a build-up of fluid in the scrotum which can cause the testicles to swell and become tender. Other potential causes of testicular swelling include infections, injury, hydroceles, varicoceles, and tumors. Treatment for testicular swelling will depend on the underlying cause. In some cases, the swelling will go away with rest and over-the-counter medications, while in other cases, more aggressive treatments such as surgery may be necessary.