A varicocele is an abnormal enlargement of the veins in the scrotum. Veins are the blood vessels that are responsible for carrying blood from the body back toward the heart. (Arteries, on the other hand, are blood vessels that carry blood from the heart to other parts of the body). Veins contain valves that keep blood flowing in the proper direction. But, when these valves fail, blood is allowed to flow backward and pool in the veins, which causes the veins to stretch and swell. When this occurs in the legs, it produces varicose veins. When it occurs in the scrotum, it produces a varicocele.
Varicoceles appear in about 15% of men between 15 and 25 years old, and most often develop during puberty. During puberty, the testicles grow very quickly and require an increased supply of blood. If the valves in the veins in the scrotum do not function optimally, the veins will struggle to transport the extra blood away from the testicles and blood will back up, thereby creating a varicocele. It is interesting to note that because the blood flow on the left side of the scrotum is greater, varicoceles tend to occur more frequently in the left testicle.
Approximately 40% of all infertile men have a varicocele. And, interestingly, as many as 80% of men with secondary infertility (those who have fathered a child, but are struggling with fertility issues in trying to conceive a second child) have a varicocele. It is not known precisely how or why varicoceles negatively impact fertility. One theory is that the pooled blood increases the temperature in the testicles, which ultimately decreases sperm count.
In many cases, a varicocele will cause no symptoms and may go undetected for many years. Some men only discover that they have a varicocele during the course of fertility testing.