The swelling is almost always in your left testicle. But you can get it on the right side or in both testicles at the same time.¹ Sometimes a varicocele is big enough for you to see the swelling, although it might disappear when you lie down. And sometimes varicoceles can't be seen at all.

You may find a varicocele if you feel your testicles. You should always see a doctor if you find a lump or swelling. It's probably just a varicocele, but there's a chance it could be cancer. But this is rare. A varicocele isn't cancer, and it doesn't usually give any serious problems.

Because a varicocele is caused by swollen veins, it can feel like a bunch of swollen tubes. Some men describe it as feeling like "a bag of worms." You can have a varicocele that's quite small, so you might not be able to feel it at all. Or you may only find out that you have a varicocele if you're having trouble starting a family, and your doctor examines you.²

Some doctors think that having a varicocele can make it harder to have children.³ There hasn't been enough research to be sure. But we do know that men who have sperm problems (such as abnormally shaped sperm), are more likely to have a varicocele.⁴

If you have a varicocele you may get pain or an ache in your testicles.² This may be worse on days when you've been standing for a long time or exercising a lot. Some men don't like how the swelling looks. But varicoceles aren't dangerous. Apart from the effect they might have on having children, they don't cause serious problems.