Varicocele and Sperm Quality: How Enlarged Veins Affect Fertility

A varicocele is an enlargement of the veins within the scrotum, most commonly affecting the left side. It is similar to varicose veins in the legs and is relatively common in adult men — found in roughly 15% of the general male population and more often among men evaluated for infertility. However, having a varicocele does not automatically mean a man is infertile or that his sperm quality is abnormal.

Some varicoceles cause no symptoms and may never require treatment. Others can be associated with abnormal semen parameters, testicular growth problems, discomfort, or reduced testosterone production.

The testes function best at a temperature slightly below core body temperature. The veins surrounding the testicle (the pampiniform plexus) help regulate this temperature through heat exchange between incoming and outgoing blood. In a varicocele, abnormal enlargement and impaired blood drainage interfere with this system.

Several mechanisms have been proposed for how varicoceles may affect testicular function: increased testicular temperature from abnormal venous blood flow; oxidative stress — associated with an increase in reactive oxygen species that may damage sperm cells; altered testicular blood flow; and hormonal and cellular changes — long-standing varicoceles may affect Leydig and Sertoli cell function, reducing testosterone production and impairing spermatogenesis. These mechanisms are likely interconnected rather than acting independently.

A varicocele may affect several semen parameters at once, although the severity and pattern of abnormalities vary between individuals. Possible effects include: decreased sperm concentration and total number, impaired motility due to oxidative stress, a higher proportion of abnormally shaped sperm (morphology), and increased risk of sperm DNA damage from oxidative stress.

Not every man with a varicocele develops abnormal semen parameters. The presence of a varicocele should therefore be interpreted together with the physical examination, semen analysis, testicular size, symptoms, and fertility history.

No. Many men with varicoceles have normal sperm production and are able to father children naturally. A varicocele becomes more clinically relevant when it is associated with: abnormal semen parameters, testicular growth or size abnormalities, persistent scrotal discomfort, infertility in a couple attempting conception, or reduced testosterone in selected patients. The size of the varicocele alone does not determine whether treatment is necessary.

Clinicians classify palpable varicoceles by size and whether they are detected at rest or only during a Valsalva maneuver: Grade 1 — small, palpable only during a Valsalva maneuver; Grade 2 — palpable at rest but not visible through the skin; Grade 3 — large, visible and palpable at rest, sometimes described as a «bag of worms»; subclinical varicocele — not detectable on exam, found only through imaging, usually scrotal Doppler ultrasound.

Importantly, a larger varicocele does not automatically mean worse fertility. Clinical findings and semen-analysis results are more useful when determining whether treatment may be appropriate.

It can, particularly in some men with larger or clinically significant varicoceles. Varicoceles may affect the function of Leydig cells, which produce testosterone in the testes. Some studies suggest that repairing a clinically significant varicocele may improve testosterone production in selected men, particularly those with low testosterone before treatment. However, not every man with a varicocele develops low testosterone, and repair should not be performed solely because a varicocele is present.

A varicocele is usually diagnosed through a physical examination, with the doctor examining the scrotum while the patient is standing and possibly performing a Valsalva maneuver. A scrotal Doppler ultrasound is used when the examination is uncertain, when another testicular condition needs to be excluded, or when more information about venous blood flow is needed. If fertility is the concern, a semen analysis is an important part of the evaluation, and hormonal testing may be appropriate when there are signs of testosterone deficiency.

Not every varicocele requires treatment. For men being evaluated for infertility, treatment is generally considered when there is a clinically palpable varicocele, infertility, and abnormal semen parameters. Subclinical varicoceles detected only on imaging are generally not treated solely to improve fertility. The main treatment approaches are microsurgical varicocelectomy and percutaneous embolization; the choice depends on the patient’s anatomy, previous procedures, fertility goals, and specialist expertise. After treatment, improvement in sperm parameters is not assessed sooner than 2–3 months, since that is how long sperm maturation takes.

Does a varicocele always cause low sperm count? No. Many men with varicoceles have normal sperm production and can father children naturally. A varicocele is more concerning when it is associated with abnormal semen parameters, testicular abnormalities, persistent pain, or infertility.

Can a Grade 1 varicocele cause infertility? It can be associated with abnormal semen parameters, but its presence alone does not mean a man is infertile. Treatment decisions should be based on semen-analysis results, fertility history, physical findings, and other factors.

Can varicocele cause azoospermia? A varicocele can be associated with severe impairment of sperm production in some men, but azoospermia is not a typical consequence of every varicocele — men with no sperm in the ejaculate require a comprehensive evaluation to determine the cause.

Can varicocele come back after surgery? Yes. Recurrence or persistence is possible after treatment, although the risk varies depending on the surgical technique and the surgeon’s experience; microsurgical techniques generally have low recurrence rates.

If you are concerned about fertility or have an abnormal semen analysis, speak with a urologist or andrologist for an individualized evaluation.