Varicocele
A varicocele is a cluster of swollen veins in the scrotum, above and behind the testicle, much like a varicose vein in the leg. It is common, it is usually on the left, and it is one of the few causes of poor sperm quality that can be corrected with an operation.
Where you'll meet it
Most men first hear the word at the examination that follows an abnormal semen analysis. A doctor feels the scrotum while you stand and bear down, and a larger varicocele feels like a soft bag of worms. Smaller ones show up only on an ultrasound scan.
Why it matters for fertility
The extra pooled blood warms the testicle, and sperm production is sensitive to heat. Over time that can lower the count, the movement and the shape of sperm. Not every varicocele does this, so a doctor always reads the finding alongside your semen analysis.
What can be done
A varicocele repair ties off or blocks the swollen veins so blood drains through healthy ones instead. It makes the most sense where the varicocele can be felt and the semen analysis is abnormal. Sperm take around three months to be made, so any improvement shows up on a repeat test months later rather than straight away.
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