It is well established that kidney stones increase the risk of developing chronic kidney disease. But a new study published in the American Journal of Kidney Diseases suggests they may also increase the risk of coronary heart disease and stroke.

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Study results found that patients with kidney stones are at 19% higher risk of coronary heart disease and 40% higher risk of stroke.

A kidney stone is an accumulation of waste chemicals in the kidney - calcium, oxalate, cystine, phosphate, xanthine and irate - that become a hard mass. Normally, these chemicals are passed out the body through urine, but they can build up if there is not enough liquid to get rid of them.

Once these stones are formed, they either stay in the kidney or move down the urinary tract into the ureter. Smaller stones can be passed out the body in urine without causing major discomfort, but larger stones may become stuck. Urine can build up behind the stones, causing a lot of pain.

The number of people affected by kidney stones in the US has been steadily increasing over the last 3 decades. It is thought that 1 in 10 people will have a kidney stone at some point in their lives.

According to the National Kidney Foundation, kidney stones have been increasingly linked to an array of health conditions, such as diabetes, obesity and hypertension.

In this latest study - led by Yanqiong Liu of the Department of Clinical Laboratory at the First Affiliated Hospital of Guangxi Medical University, China - the researchers wanted to see whether kidney stones influenced the risk of cardiovascular problems, such as coronary heart disease (CHD) and stroke.

Women with kidney stones 'at higher CHD risk than men'

To reach their findings, Liu and her team analyzed data of more that 3.5 million patients and identified 50,000 who reported having kidney stones.

They found that patients with kidney stones were 19% more likely to experience a CHD incident - defined as having a heart attack or arterial bypass surgery - and were 40% more likely to have a stroke, compared with patients who did not have kidney stones.

"People should be concerned about kidney stones," says Liu. "Evidence suggests an association between kidney stones and incident cardiovascular disease, even after adjusting for other cardiovascular risk factors."

But the team was even more surprised to find that women with kidney stones were at much higher risk of experiencing CHD incidents than men - particularly heart attack. According to Liu, this finding is "unexpected and difficult to explain."

As such, she says further studies are required to confirm this association and assess the underlying mechanisms.

Commenting on the team's findings, Thomas Manley, director of scientific activities at the National Kidney Foundation, says:

"Kidney stones are common, and with their association to coronary heart disease and stroke found in this study, it suggests that a thorough cardiovascular assessment should be considered in patients who develop kidney stones."

He adds that these findings also suggest that individuals should adopt lifestyle modifications that could reduce the risk of both kidney stones and cardiovascular problems, such as weight loss, a healthy diet, smoking cessation and exercise.

Last year, Medical News Today reported on a study claiming sugary drinks increase the risk of kidney stones.