Why would a man have swollen testicles?

It is rare... To have two swollen testicles, which can be caused by infection of both testes or the appearance of cancer in both of them. It is much more common to have fluid build up around the testicle, swelling up the scrotum on one or both sides and making the actual testicles difficult to feel. If you have this problem, please see your physician or urologist for an examination.