M.D. Recent research shows that most cases of swollen testicles do not need to be corrected by surgery. Less common causes include infection or a tumor. Sperm travels from the testicles to the outside in a tube that extends underneath the skin to the groin and then passes through the belly wall to come out through the penis. Hydroceles are usually caused by a hernia in the belly wall causing fluid to leak down the cord and collect around the testicle. The usual treatment is to surgically correct the hernia by closing the opening in the belly wall.
Nobody knows whether varicoceles cause infertility in men.
The old argument was that the testicles are outside the body because they cannot tolerate normal body temperature of 98.6 degrees. Large veins carry hot blood from the body to heat the testicles and prevent them from making active sperm. Therefore doctors cut out the veins so the , temperature drops, allowing the testicles to produce active sperm. However, there is no good data to show that cutting out varicoceles increases fertility. So if you are a man with large veins around your testicles and are trying to get your wife pregnant, you should not get surgery to cut out these veins unless all other tests fail to yield a cause.