Varicoceles are abnormally enlarged veins draining the testicle, similar to varicose veins seen in the legs. They are more common on the left side because the left and right testicles have different drainage pathways. There are two types of blood vessels in the human body, arteries (which bring oxygen-rich blood to the testicle) and veins (which take oxygen-poor blood away from the testicle). Because these veins are carrying blood directly against gravity, and with minimal muscle backing, they have a tendency to dilate. This is called a varicocele. In some men, these dilated veins will not harm sperm production. But in other men, this will cause a pooling of blood in the testicles, which can heat up the testicles or cause the pooling of toxins. Since the testicles are where sperm are formed, this can have an adverse effect on sperm production and function.

Surgical varicocele repair (varicocelectomy) can stop further deterioration of sperm production, and will often improve sperm quality. This procedure is performed under an operative microscope. This allows for identification of the the precise veins that are dilated, and minimizes the risk of complications, such as damage to the arteries. This surgery is done under a general anesthetic and usually takes around 90 minutes.

Overall, the medical literature shows that approximately 2/3 of men will have an improvement in their semen parameters after varicocele repair. In addition, emerging literature shows that varicocele repair improves reproductive outcomes, including pregnancy rates after Intrauterine Insemination (IUI), In Vitro Fertilization (IVF) and Intracytoplasmic Sperm Injection (ICSI).

Accumulating literature also shows that varicocele repair may improve testosterone production.