A varicocele is a dilated (enlarged) group of veins in the scrotum. Just like some people have dilated or "varicose" veins in their legs, some men have dilated veins in their scrotum. The dilated veins are filled with excess blood. Men with varicoceles may notice a heavy, dragging, aching feeling in the scrotum ("ball sack") at the end of the day.

Varicoceles are the leading fixable cause of male infertility. Fifteen percent of all men have varicoceles while 40% of men experiencing primary infertility (never fathered a child) have varicoceles. Eighty percent of men experiencing secondary infertility (have fathered a child) have varicoceles. This may be due to the fact that varicoceles cause progressive damage to the testicle and a progressive decrease in the quality and quantity of sperm produced. Of those men who have varicoceles, forty-five percent have varicoceles on both sides; fifty percent have a left-side varicocele; and five percent have a varicocele on the right side alone.

HOW DO VARICOCELES DEVELOP?

Varicoceles develop most often during adolescence. During this time, the testes grow dramatically and need more blood to supply the increased need for oxygen and nutrients. Since more blood is going into the testes, there is also more blood draining away from them. If the valves that drain blood from the testes are not functioning properly, the blood will pool in the scrotum.

If large varicoceles develop after adolescence, a man must be examined to make sure that there is no tumor in the abdomen compressing the veins, preventing the blood from properly flowing back to the heart.

WHY ARE VARICOCELES IMPORTANT?

Varicoceles may cause:

• Varicoceles may cause infertility through a significant decrease in the quality and quantity of sperm.
• Varicoceles may cause damage to the testicles; they may not grow appropriately. This damage is progressive; it will often worsen over time. If an adolescent has a one-sided varicocele, the testis on that side may not develop as much as the other side and may be significantly smaller. This is a serious consideration because smaller testes generally produce significantly less sperm than normal-sized testes. If the varicocele is repaired during adolescence, the testis may experience catch up growth and normalize in size. If it is repaired at a later age, the testis will not improve in size, though it may often improve in sperm production. The sperm production, however, will still not improve to the same extent it would have had it been repaired earlier.
• Varicoceles may cause discomfort leading to a heavy, dragging feeling in the scrotum.
• Varicoceles can damage the cells that make testosterone and may lead to a decreased overall testosterone level. Testosterone, the main male hormone, is responsible for a man's "secondary male characteristics" (i.e., increased muscle mass and tone, level of sexual interest, body hair).

VARICOCELES AND INFERTILITY

Varicoceles decrease fertility, but it is unclear why. There are several possible theories:

• Increased temperature of the testicles: The testicles are located in the scrotum, which regulates their temperature. They are maintained at a temperature slightly below body temperature. (This is probably why they are located outside the body rather than inside the body where they clearly would be better protected.)
  
  Since the varicoceles surround the testes and the blood is at body temperature, varicoceles will keep the testes at a temperature that is higher than is beneficial for them. Even if a man has only one varicocele, the whole scrotum is warmed by the blood and both testicles can be negatively affected.
  
  In general, larger testicles make more sperm than smaller testicles. Often, however, you see men who have a large one-sided varicocele that has damaged the testis on one side, making it smaller. The small testis makes significantly less sperm than the normal one. However, even in the "normal" one, the sperm quality is often very low. The varicocele is not only damaging the testis on the side where it is found, but also suppressing the sperm production on the opposite (better) side.
  
  When a varicocele is repaired, the blood is no longer able to flow back into the scrotum. This affects not only the testes on that side, but also the opposite side. With this normalization of temperature, there may be some dramatic improvement in sperm production. It is likely that this improvement comes mostly from improved production in the larger, better testicle.

• Increases waste products back- flowing into the testicles. The veins draining the testicles connect into larger veins. On the left side, they drain into the kidney vein, which is draining blood from the kidney. The blood from the kidney carries waste products, which may then drain into the scrotum. This may negatively affect sperm production.

It used to be thought that a varicocele would result in a stress pattern that would appear in the semen analysis (i.e., a decreased percentage of moving sperm or sperm with abnormally shaped heads). Recent studies conclude that varicoceles affect virtually all of the parameters in a semen analysis (i.e., the concentration, motility, forward progression, and morphology). The varicoceles also affect the functioning of the sperm, although this cannot be tested by a routine semen analysis. Very specialized testing of the sperm functioning may be performed, although this is expensive and its use is debated.