A varicocele is a swelling in the veins above the testicles. It is similar to having varicose veins in the legs. The swelling occurs when too much blood collects in the veins because they are damaged. A varicocele most often occurs around the left testicle.
The scrotum is a sac of skin that covers the testicles — the male sex organs that produce sperm and the male hormones. Blood vessels in the scrotum carry blood to and from the testicles. The vessels that carry blood away from the testicles are called veins.
The veins that carry blood from the testicles extend up into the groin. That means the blood has to travel upward a long way. Valves in the veins act like gates to keep the blood from flowing back toward the testicles. In some men, these valves don’t close fully. Or the muscles in the walls of the veins may be weak. Then some blood flows back into the scrotum and collects in the veins above the testicles. This makes the veins enlarge.
A varicocele often causes no symptoms at all. Or it may cause an achy or heavy feeling in the scrotum. The pain may be worse later in the day or after standing for a long time. You may also see swollen veins just under the skin in the scrotum.
When blood collects in the veins above the testicles, changes occur that can reduce the number and the quality of the sperm. In many cases, sperm count improves after treatment.