Health2 min(s) read
Published 15:45 22 May 2026 GMT
Healthcare experts are raising awareness about a 'bag of worms' condition affecting the testicles that is believed to impact up to one in five men and may contribute to fertility problems.
Varicoceles, a common condition, occurs when veins inside the scrotum become enlarged, disrupting the environment needed for healthy sperm production. According to the NHS, the condition most often develops on the left side of the scrotum, although it can appear on either side.
NHS Milton Keynes Hospital explains: “It is not certain what causes varicocele. It is possible that a valve defect in the veins may be causing the veins to widen.”
The hospital also notes: “Varicocele is not always visible but it does affect the blood flow in the testicles. If it becomes enlarged, it could cause the testicles to shrink and possibly reduce your fertility. Varicocele repair may improve fertility, but this is not guaranteed.”
Speaking to Metro, urologist Professor Suks Minhas said one of the most common warning signs is “pain and discomfort in the left testicle,” adding that around 90 percent of men with the condition first experience symptoms on the left side.
He explained that other symptoms can include “a dull or aching pain, swelling, and testicular atrophy.” Larger varicoceles, he said, have sometimes been compared to “a bag of worms or twisted veins.”
However, some men may not experience any symptoms at all.
Professor Ramsay also explained to Metro how the condition can affect fertility by effectively “heating the testicle.” He said: “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.”
He added: “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.”
According to the expert, oxidative stress can damage sperm quality by allowing harmful chemicals to mix with seminal fluid. Professor Ramsay warned that varicoceles may also “disturb some of the other functions of the testicles.”
Doctors say treatment can often help restore normal function and may improve fertility outcomes for some men.
