You don’t think twice when you need to give yourself a quick below-the-belt adjustment. But what if something doesn’t feel quite right with one of your boys?

If one of your testicles feels like a bag of worms, you might have a condition called a varicocele. Read on to find out more about what this condition means for your nether regions.

Related: The Men’s Health Guide To Erectile Dysfunction—the Only Resource You Need If You’re Serious About Getting Your Boner Back.

What Are Varicoceles?

A varicocele is a set of abnormally dilated or enlarged blood veins in your scrotum—think of them like spider veins for your balls.

About 10 to 15 percent of men have varicoceles, estimates Lawrence Hakim, M.D., chairman of the department of urology at Cleveland Clinic Florida.

They develop during periods of rapid growth—say, during puberty—possibly due to malfunctions in the valves of the vessels that cause the blood to pool in the veins.

Varicoceles are often not detected until later in life, when they grow large enough to cause discomfort or fertility problems.

Why Varicoceles Can Be Harmful

The pooling of blood can be damaging because it causes your scrotum to overheat.

Normally, your balls remain a few degrees cooler than the rest of your body, thanks to the veins that normally drain your testicles, says Dr. Hakim.

But when that vein dilates, the blood pools and raises the temperature one or two degrees.

Related: The Complete User’s Manual To Your Balls

It doesn’t sound so serious, but it’s bad news for your baby-makers: Men with varicoceles have a sperm count that’s 41 percent lower than guys without the bulging veins, an Italian study found.

Their sperm also didn’t move as quickly, which can make pregnancy harder to achieve.

Symptoms of Varicoceles

So how do you know if you have one? There are three different grades, or severities, of varicoceles, which have different characteristics, explains Paul Turek, M.D., a California-based urologist.

Grade 3 varicoceles are the largest and most noticeable, he says. The veins in your scrotum are so dilated and full of blood that you can see them from across the room, Dr. Turek says (though we don’t recommend asking anyone except a urologist to confirm this). To the touch, they will feel thick and lumpy, like a bag of worms.

Grade 2 varicoceles aren’t as noticeable, but they may make your testicle feel full and ropey. Grade 1 varicoceles are quite small and difficult to detect on your own. You may not notice any outward symptoms, but a specialist could identify it during an exam.

Sometimes larger varicoceles can also cause low-level, nagging scrotal discomfort at the day’s end, due to a buildup of pressure in the veins, Dr. Turek says.

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There are no known risk factors for developing these lesions, he says.

But infertile men who smoke are more than twice as likely to have a varicocele than their non-smoking counterparts, according to a recent Iranian study. So if you’re worried about your balls, it can’t hurt to stub out the smokes.

How to Treat Varicoceles

The good news is that smaller, hard-to-detect varicoceles don’t pose much trouble and don’t necessarily need to be fixed, Dr. Turek says.

“The bigger they are, the more harmful they are to fertility,” he says.

That’s partly because more noticeable varicoceles means more blood is hanging out in your scrotum and making it warmer, he explains.

For bigger ones that may be impeding your fertility—or causing you discomfort—you’ll need surgery to get rid of them.

Surgery to fix the problem microscopically in the groin, the method with the lowest recurrence rate, is minimally invasive. Your doctor will tie off the flawed vein to divert the blood flow from the testicle to a group of normally-functioning veins.

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Recovery takes about two days. Afterwards, your pain should disappear and your fertility should be restored.

“Varicoceles are probably the most common fixable, reversible cause of male-factor infertility,” Dr. Hakim says.

It takes about three months to make a new batch of sperm, he adds. Within four months of fixing the varicocele, your semen parameters can return to normal levels.

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