Why do varicoceles cause male infertility?

As a urologist and male infertility specialist, I see many men with varicoceles, so I am frequently talking to patients about varicoceles. Thus, varicoceles are good subject for the blog.

Varicoceles are dilated veins that surround the testicular artery within the spermatic cord, the cord by which the testicles hang from the body. The testicles are located in the scrotum--the sack--because they need to be cooler than the rest of the body. Varicoceles make the testicles too hot, and this heat, among other things, impacts the testicles' ability to produce healthy sperm.

Varicoceles are similar to varicose veins in the legs, though they are in the scrotum. When the veins get large, blood flow within the vein can be affected in a way that allows toxic metabolities to accumulate. Some of these metabolites include molecules called reactive oxidative species--or oxidants. Other chemicals include substances such as trace metals present in certain food-stuffs, cigarette smoke, and the environment in general. In some men, a build up of these toxic metabolites can have a deleterious effect on sperm and the testicles.

The presence of a varicocele on one side affects sperm production from both testicles. Why this is, no one knows. Varicoceles are more common on the left cord. This is because of the anatomy of venous drainage from the left testicle back to the vena cava--the largest vein in the body--by way of the left renal vein. Varicoceles on the right side only are uncommon, though bilateral varicoceles exist frequently.

While 20% of all men have varicoceles, 35 % of men with fertility problems have them. Correction of the varicoceles in men who have a problem--such as a low sperm count or difficulty inpregnating their wives--can result in improvements in sperm counts, motilities, and morphologies in the majority of affected men, even in severe cases of male factor infertility. Most importantly, perhaps, is that >50% of couples can expect to become pregnant naturally within 1 year after varicocele repair. Those couples who do not achieve a natural proegnancy will ultimately require assisted reproductive help in the form of IUI, IVF, or ICSI. The presense of varicoceles negatively affects success rates with these assisted reproductive techniques and fixing the varicocele improves pregnancy rates for these couples.

Varicoceles are typically not visible to the eye, at least not unless they become very large. Instead, the urologist can feel them on physical exam. Sometimes the patient will notice the varicocele themselves and comment that they feel a swelling or "a bag of worms" in their scrotums.

Varicocele surgery is outpatient and ambulatory. Most patients with desk type jobs may return to work in 2-3 days; a bit longer for patients with more physical jobs. Men may return to sexually activity a few days later and can expect improvement in the sperm quality within 6-12 months.