‘Bag of worms’ testicle condition can harm your fertility — and 20% of men have it

Between 15% and 20% of all men reportedly have varicoceles (Picture: Getty Images)

According to the NHS, around one in seven couples have difficulty conceiving.

And, while discussions often focus on women’s bodies, experts are increasingly pushing for there to be greater education around the challenges faced by men.

One of the conditions affecting male fertility is varicoceles — a surprisingly common issue, present in 15 to 20% of all men.

A varicocele is when a vein or collection of veins in the scrotum becomes enlarged, disrupting the optimal environment for sperm.

The National Institutes of Health estimates that up to 40% of men with primary infertility have varicoceles, but with infertility still largely viewed as a women’s issue, many cases continue to go undiagnosed.

Up until recently, the National Institute for Health and Care Excellence (NICE) guidelines regarding managing male factor fertility problems stated that treating varicoceles would not actually improve a couples’ chance of getting pregnant.

However, this changed in March 2026. Doctors are now being advised to ‘consider radiological or surgical treatment for individuals with male reproductive organs who have varicocele detected on clinical examination.’

While the condition is harmless for most, it can cause male infertility issues (Picture: Getty Images)

What are varicoceles?

Urologist Professor Suks Minhas tells Metro that the easiest way to describe a varicocele is as a ‘collection of dilated veins around the testicle’.

While many men may be asymptomatic, he adds that ‘the first symptoms are usually pain and discomfort in the left testicle, with 90% occurring on the left and 10% on the right side. However, they can occur on both sides.

Other common sensations may include a dull or aching pain, swelling, and testicular atrophy. Larger varicoceles have also been described as feeling like a bag of worms or twisted veins.

But Professor Suks also notes that ‘not all varicoceles cause harm or problems.’

Many men with varicoceles may not ever experience any symptoms (Credits: Getty Images)

How do varicoceles impact fertility?

Metro also spoke with Professor Ramsay — a urologist who’s worked within the male fertility field for over 30 years.

According to him, the reason varicoceles may impact fertility is principally to do with ‘heating the testicle.’

‘This happens because there is more blood around the testicle because the veins are dilated and distended, and the flow of the blood is coming from above in the abdomen, where the blood is warmer.

‘Testicles are in the scrotum because they like around 3°C below core temperature. But varicoceles warm the testicles and in so doing, causes oxidative stress.’

Oxidative stress, according to Professor Ramsay, is when certain chemicals get into the seminal fluid and reduce sperm quality.

He also adds that big varicoceles might ‘disturb some of the other functions of the testicles’ including testosterone output. However, stresses that if treated, levels should return to normal.

Approximately 1 in 14 men in the UK are affected by infertility (Picture: Getty Images)

What causes varicoceles?

When asked about the role this condition plays in infertility, Professor Suks went as far as to say that varicoceles are considered ‘one of the biggest conundrums in urological practice’ due to the fact that doctors do not know the true cause behind them.

He adds: ‘It is very interesting that while some men can have large varicoceles and remain fertile, others with varicoceles do not maintain fertility. We do not know the full answer to this.’

But from the perspective of both experts, NICE’s updated guidelines on actually treating the condition are welcomed.

Professor Ramsay particularly feels that encouraging doctors to consider the role varicoceles might play in fertility could be helpful for those who have not yet gone through IVF.

‘If an individual has a big varicocele, and his female partner is 35 and not getting pregnant, there’s a strong argument to repair the varicocele and wait for the benefit, to potentially avoid IVF.

‘There aren’t many reasons for not treating a varicocele.’

Professor Ramsay concludes: ‘If you’re going to a fertility unit to be seen by a gynaecologist, you must ask them whether or not they’ve considered if the man has a varicocele.

‘Treatment like IVF is actually being confused with a possible solution. So patients, particularly men, don’t get treated.

‘The response of the National Health Service is to say “just do IVF” and they call that the treatment, when in reality it’s not. It may be, when it works as a solution, but what about when it doesn’t?’

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