A varicocele is like varicose veins of the small veins (blood vessels) next to one testicle (testis) or both testicles (testes).
What is a varicocele?
A varicocele is a collection of enlarged (dilated) veins (blood vessels) in the scrotum. It occurs next to and above one testicle (testis) or both testes (testicles).
Varicoceles affect the veins that travel in the spermatic cord. The spermatic cord is like a tube that goes from each testis up towards the lower tummy (abdomen). You can feel the spermatic cord above each testis in the upper side of the scrotum. The spermatic cord contains the tube that carries sperm from the testes to the penis (the vas deferens), blood vessels, lymphatic vessels and nerves.
Normally, you cannot see or feel the veins in the spermatic cord that carry the blood from the testicles. If you have a varicocele, the veins become bigger (they dilate) and this makes them more noticeable. It is similar to varicose veins of the legs. The size of a varicocele can vary. A large varicocele is sometimes said to look and feel like a bag of worms in the scrotum.
What causes a varicocele?
In most cases, the reason why the veins (blood vessels) become larger is because the valves of the small veins in the scrotum do not function well. There are one-way valves at intervals along the veins. The valves open to allow blood to flow towards the heart, but close when blood flow slows to stop blood flowing backwards.
If these valves do not work well, blood can flow backwards (due to gravity) and pool in the lower parts of the vein to form a varicocele. (This is similar to how varicose veins form in legs.)
It is not clear why the valves do not work well.
A varicocele may (rarely) develop if there is a blockage of larger veins higher in the tummy (abdomen). This puts back-pressure on the smaller veins in the scrotum which then enlarge (dilate). This is only likely to occur in men older than 40. For example, if a varicocele suddenly develops in an older man, it may indicate a tumour of the kidney has developed which is pressing on veins.
It must be stressed, the vast majority of varicoceles develop in teenagers and young men and are not due to a serious condition.
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How is a varicocele diagnosed?
The diagnosis is made by a doctor's physical examination. A colour duplex ultrasound scan (a scan using ultrasound to look at blood flow in an area) is sometimes done to confirm the diagnosis.
A varicocele is associated with some cases of infertility. Therefore, a semen test may be asked for if you are part of a couple being investigated for infertility.
In the rare situation of a varicocele first developing in a man aged over 40, tests to check out a possible underlying cause may be advised. Also, a solitary right-sided varicocele is unusual. If this occurs, you may need some tests to rule out any unusual cause.
See also the separate leaflet on Scrotal Lumps, Pain and Swelling (Hydrocele, Varicocele, Testicular Torsion).
When does a varicocele need treating?
If a varicocele is causing no symptoms or problems, then it is best left alone. It is usually harmless but there are some situations in which it can cause concern.
Is a varicocele dangerous?
Possible cause of infertility
Studies have shown that there is a higher percentage of infertile men with a varicocele compared with those who do not have a varicocele. The reason for this is not clear. One theory is that the pooled blood causes a slightly higher temperature in the scrotum than normal. This may reduce the number and quality of sperm production made by the testicle (testis), which can affect fertility. Even if you have a varicocele only on one side, both testicles (testes) can be warmed by the increased amount of blood pooled in the enlarged veins (blood vessels).
Research has shown that treating a varicocele usually improves sperm quality. However, most men with a varicocele are not infertile.
Currently it's recommended that a varicocele should be treated if:
- It's obvious on examination (as opposed to just showing up on a scan).
- Sperm count is low; you've been infertile for two years or more.
- Your infertility is otherwise unexplained.
If a large varicocele develops in a teenager, the testis on the side of the varicocele may not develop as much as would be expected. For example, an annual measurement of the testes may be advised. The testis may end up being smaller than normal. This may contribute to infertility too.
Sudden onset of a varicocele in an older man
Very rarely, a varicocele quickly develops as a symptom of a blockage of a larger vein in the tummy (abdomen) - see above. This would normally only occur in men over the age of 40.
If there is just mild discomfort, supportive underpants (rather than boxer shorts) may help to ease or prevent discomfort.
It is advised that you should be referred to a urology specialist if:
- A varicocele appears suddenly and is painful (urgent referral).
- The varicocele does not drain when lying down.
- There is pain or discomfort.
Adolescents with a varicocele should be referred to a urologist:
- If there are concerns about the testis on that side being small.
- If there is uncertainty about the nature of the scrotal swelling.
- If you are concerned by the appearance or symptoms.
It is not recommended that the male partner of an infertile couple be referred for varicocele surgery as a form of fertility treatment, as it does not improve pregnancy rates.
Treatment involves tying off the veins (blood vessels) that are enlarged. Another method of treatment is to use a special substance injected into the veins to block them. Both methods are usually successful. Your surgeon will advise on the pros and cons of the different techniques.
However, after successful treatment, some men have a return (recurrence) of a varicocele months or years later. This is because the veins left behind to do the job of taking the blood from the testes may themselves enlarge (dilate) with the extra blood they will now have to carry. A recurrence can be treated in the same way as the first time.
Further reading and references
Fertility - Assessment and treatment for people with fertility problems; NICE Guidance (February 2013, updated September 2017)
Varicocele; NICE CKS, December 2021 (UK access only)
D'Andrea S, Micillo A, Barbonetti A, et al; Determination of spermatic vein reflux after varicocele repair helps to define the efficacy of treatment in improving sperm parameters of subfertile men. J Endocrinol Invest. 2017 May 25. doi: 10.1007/s40618-017-0695-x.
Kolon TF; Evaluation and Management of the Adolescent Varicocele. J Urol. 2015 Nov194(5):1194-201. doi: 10.1016/j.juro.2015.06.079. Epub 2015 Jun 25.