When you're making a quick adjustment below the belt, you might discover something unexpected: Your balls feel like a bag of worms.

Are you surprised? Definitely. But it's not as uncommon as you might think: Varicoceles—or enlarged blood vessels in your scrotum—affects about 15 percent of healthy men.

In most cases, varicoceles won't cause you any immediate problems. But new research out of Stanford University School of Medicine suggests that the presence of these enlarged veins in your balls might actually be signaling something serious about your health.

In the study, researchers analyzed health insurance claims data from 4,459 men with varicoceles and 100,066 guys without the enlarged veins. After three years, they discovered that men with varicoceles were significantly more likely to develop heart disease, diabetes, and high cholesterol than guys without the condition.

But that only held true for those with symptomatic varicoceles—guys who had low testosterone, infertility, or testicular pain as a result of their enlarged blood vessels down below. In fact, men with symptomatic varicoceles were 38 percent more likely to develop heart disease, 91 percent more likely to develop diabetes, and 17 percent more likely to develop high cholesterol than healthy, fertile men without varicoceles.

The pooling of blood caused by the vessel dilation can make your scrotum to overheat, potentially damaging your sperm, as we previously reported. It could also cause a buildup of pressure in your veins, leading to discomfort in your balls.

Still, it's worth noting that most varicoceles don't cause any clinical symptoms, says study author Michael Eisenberg, M.D. In fact, only about two to 10 percent of varicoceles cause pain, according to Indian researchers.

And in the study, guys with varicoceles that didn’t cause them any problems had no increased risk of those conditions compared to men without the enlarged veins.

So why the link between enlarged veins in your balls and some pretty serious health conditions throughout your entire body?

Well, the very definition of varicoceles—enlarged veins in your scrotum—makes it pretty unlikely that it’s actually causing issues like heart disease, says Dr. Eisenberg. Heart disease, of course, develops when plaque buildup in your coronary arteries cause them to narrow.

The more likely explanation, then, is that the development of varicoceles is actually a marker of another condition, like low testosterone or oxidative stress, an overabundance of cell-damaging free radicals in your body. Both of these conditions can lead to heart disease, too, he says.

Take oxidative stress, for instance. This occurs when your body is unable to efficiently clear out waste products that result from metabolic breakdown in your cells. The result? Body-wide inflammation.

“A slightly heightened inflammatory state has been associated with cardio-metabolic disease,” Dr. Eisenberg says. Theories also suggest that these inflammatory compounds may be related to varicoceles, too, and that the accumulation of them can damage healthy tissue, he says.

More research needs to be done to understand why the link between varicoceles and heart disease and diabetes exists, and what doctors may be able to do for guys who have them to reduce their risk of serious health issues down the line, Dr. Eisenberg says.

“But if a man has a varicocele, it’s certainly reasonable to see a physician for an evaluation of symptoms and a discussion of treatments that may improve his condition,” he says.

While most of the varicoceles don’t cause any symptoms, the ones that do can be treated by surgery (though it's unclear right now whether treating your varicocele will improve your heart risk). Your doctor simply ties off the affected vein to divert blood flow to a group of healthy veins instead.