The number of Americans suffering from kidney stones has almost doubled since 1994, researchers report, and the obesity epidemic is the most likely reason why.
About one in 11 Americans now develops kidney stones, according to scientists from the University of California, Los Angeles and RAND Corp. In contrast, only one in 20 Americans developed kidney stones back in 1994, they noted.
"Kidney stones are becoming a very common health condition in the United States," said lead researcher Dr Charles Scales Jr., a Robert Wood Johnson Foundation/US Department of Veterans Affairs clinical scholar in the David Geffen School of Medicine departments of urology and medicine at UCLA. They are more common than heart disease, stroke and diabetes, he added.
What is a kidney stone?
A kidney stone is like any small rock, Scales said. "It's an accumulation of crystals of substances that are dissolved in urine and for reasons that are not well understood, form rocks," he explained. Kidney stones are a condition that results from risks associated with diet and lifestyle.
"People with a history of kidney stones also are more likely to have histories of diabetes, obesity and gout," he said.
Usually, severe pain is the first sign of a stone, Scales said, and as many as 50% of people who develop a first kidney stone develop others.
"To prevent stones from forming, the most important things are diet and lifestyle interventions such as drinking plenty of fluids, eating a low animal-protein diet and having only a moderate amount of salt," Scales pointed out.
The finding was presented this week at the American Urological Association meeting in Atlanta and published in the July issue of the journal European Urology.
How the study was done
For the study, Scales' team used data from the US National Health and Nutrition Examination Survey to identify the rate of kidney stones in the United States.
The substantial increase in kidney stone cases is most likely due to increases in obesity, diabetes and gout, which are risk factors for the condition, the researchers said.
Dr Brian Matlaga, an associate professor of urology at Johns Hopkins University School of Medicine and author of an accompanying journal editorial, commented that "between 1994 and 2010, the increase in kidney stones was just about 63%, which is really a staggering increase when one thinks about it."
Matlaga added, "We are beginning to recognise that kidney stones are a systemic condition, and are associated with other disorders such as diabetes and obesity that have significant health implications." In addition, there is a need for research to identify the causes of kidney stones and better ways to prevent them, he noted.
"Over the past decades, we have not seen great advances in non-surgical treatments for [kidney] stone disease," Matlaga said.
"Kidney stones are increasing at a great rate, and although we have classically thought of a kidney stone as 'just a kidney stone,' this disorder should probably be viewed as a systemic disease and associated with other important diseases such as diabetes and obesity, both of which can have a deleterious effect on our patients' health," he suggested.
Dr Arthur Smith, chairman emeritus of urology at North Shore-LIJ Health System in Lake Success, N.Y., said he was not surprised by the finding.
Obesity and kidney stones
"Obesity plays a very big role in stone formation. The biggest problem is that people who are obese tend to have more salt and animal protein in their diet, and this predisposes them to stone formation," Smith said.
Usually, the first sign of a kidney stone is pain. Kidney stones can cause severe pain or infection or both, and both result in pain, he explained.
Current treatment for kidney stones varies by the size and location of the stone and its consistency, he noted. Stones can be removed surgically or through shock waves that are applied outside the kidney to break up the stone, Smith said.
To prevent further stones, the best advice is to alter one's lifestyle, he noted. This includes a low-salt and low-meat diet as well as drinking a lot of water or lemonade. Lemonade is high in citrate, and citrate limits stone formation, he added.
Living with kidney problems
For more information on kidney stones, visit the National Kidney Foundation.
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