The veins that drain each testis form a mesh called the pampiniform plexus. When the valves in those veins do not work well, blood pools and the veins widen. Large varicoceles can look and feel like a 'bag of worms' above the testis, especially when standing; small ones may only be seen on ultrasound.
Most varicoceles are on the left, largely because of the way the left testicular vein drains into the kidney vein. A varicocele that appears suddenly, sits only on the right, or does not shrink when you lie down is worth getting examined promptly.
Plenty of men with a varicocele have normal fertility and never know it is there. It becomes relevant when it comes with an ache, a shrinking testis or abnormal semen results.
How does a varicocele affect fertility?
It is linked with poorer semen quality, smaller testes and lower testosterone production, though not every man is affected. Exactly how it causes harm is still not fully explained.
In a World Health Organization study of 9,034 men attending infertility clinics, a varicocele was found in 25.4% of men with abnormal semen compared with 11.7% of men with normal semen. It was associated with smaller testicular volume, poorer sperm quality and reduced function of the Leydig cells, which make testosterone.1 Interestingly, spontaneous pregnancies were just as frequent whether or not the man had a varicocele.1
A 2021 Cochrane review notes that the mechanism has yet to be satisfactorily explained.2 The leading theories involve extra heat around the testis and oxidative stress, which may help explain the link with sperm DNA fragmentation.
Does varicocele repair improve fertility?
Repair may improve the chance of pregnancy, but whether it increases live births is uncertain. Decisions are individual, weighing semen results, the partner's age and other options.
The Cochrane review, covering 48 randomised trials and 5,384 participants, found that treatment may raise pregnancy rates compared with no or delayed treatment: from about 21% to somewhere between 22% and 48%. That evidence was low certainty, and the effect on live birth was very uncertain.2
Among surgical approaches, microsurgical subinguinal repair probably gives slightly higher pregnancy rates and fewer recurrences than other techniques.2 A separate meta-analysis of 19 studies found that repair lowered sperm DNA fragmentation by about 7 percentage points on average, with bigger drops in men who started high.3
- Microsurgical repair: the veins are tied off through a small groin incision using a microscope
- Radiological embolisation: the veins are blocked from inside using a catheter
- Monitoring: often reasonable for a small, painless varicocele with normal semen results
What symptoms does a varicocele cause?
Often none. When there are symptoms, they tend to be a dull ache or heaviness that builds after standing or exercise and eases when lying down.
You might notice the veins themselves, or a difference in size between the two testes. Some men have a varicocele treated for discomfort alone, separate from any fertility question.
Because varicoceles are associated with reduced Leydig cell function,1 symptoms of low testosterone are worth mentioning. The EAU guideline advises that infertile men are screened for modifiable problems such as hypogonadism.4
When should you see a doctor?
See a GP if you notice swelling, an ache or a size difference in your scrotum. Any new lump should be checked, whatever you think it is.
An examination standing and lying down, sometimes with an ultrasound, is usually enough to confirm a varicocele. If you are trying to conceive, ask for a semen analysis at the same time so any decision about treatment rests on your actual results rather than the finding alone.
Common questions
Can a varicocele go away on its own?
Not usually, but many never cause problems and need no treatment. If it is painless and your semen analysis is normal, monitoring is a common approach.
Does a varicocele lower testosterone?
It can. In the WHO study, varicoceles were associated with reduced function of the Leydig cells that produce testosterone.1 If you have symptoms such as low libido or fatigue, talk to a doctor about a blood test.
Is a varicocele dangerous?
Rarely. It is a benign vein problem, but one that appears suddenly, sits only on the right or does not empty when you lie down should be examined promptly to rule out anything pressing on the veins.
Read more on this
Lifestyle factors that affect male fertility: a practical guide
How long does it take sperm to regenerate?
Sources
- World Health Organization. The influence of varicocele on parameters of fertility in a large group of men presenting to infertility clinics. Fertil Steril. 1992;57(6):1289-93. PubMed
- Persad E, O'Loughlin CA, Kaur S, et al. Surgical or radiological treatment for varicoceles in subfertile men. Cochrane Database Syst Rev. 2021;4(4):CD000479. PubMed
- Lira Neto FT, Roque M, Esteves SC. Effect of varicocelectomy on sperm deoxyribonucleic acid fragmentation rates in infertile men with clinical varicocele: a systematic review and meta-analysis. Fertil Steril. 2021;116(3):696-712. PubMed
- Minhas S, Bettocchi C, Boeri L, et al. European Association of Urology Guidelines on Male Sexual and Reproductive Health: 2021 Update on Male Infertility. Eur Urol. 2021;80(5):603-620. PubMed
Not medical advice. Written by Eric Stephens from the research cited above; not reviewed by a doctor. If something worries you, see a GP.