from Gray's Anatomy
A varicocele is mass of enlarged and dilated veins in the testicle that essentially feels like a bag of worms. It is generally not harmful and usually not painful. Approximately 15 percent of males have this condition which almost always occurs on the left side. A varicocele usually develops at puberty (age 15) but can occur earlier.
A varicocele can be found in 42% of infertile men. About 15% of normal, fertile men also have a varicocele, a fact which complicates the relationship between infertility and varicoceles.
A varicocele often produces no symptoms. Rarely, it may cause pain that may worsen over the course of a day because of physical exertion and typically is relieved by lying down on your back. With time, varicoceles may grow larger and become more noticeable.
The varicocele can be corrected by a simple surgical procedure, performed routinely on an outpatient basis, called a varicocelectomy. It remains the most correctable factor when poor semen quality is discovered, but since it is very common, the operation should only be considered if other infertility risk factors are absent.
While you are under anesthesia, a small incision is made in the lower abdomen or groin area. Some doctors use a microscope to better visualize the varicocele and help avoid testicular damage. During varicocelectomy, the doctor ties off the swollen veins so blood no longer pools, allowing the testicle to better maintain proper temperature.
An improvement in semen quality can be expected in roughly 67% of patients who have varicocele ligation, with improvement most likely to be an increase in sperm motility rather than sperm count. The pregnancy rate following varicocele repair is approximately 40%, with pregnancy occurring an average of 9 months after surgery.