The symptoms of kidney stones can range from extremely inconvenient to acutely painful to life-threatening. According to the National Kidney Foundation, 1 in 10 Americans will have at least one during his or her lifetime and more than half a million people each year attend ER with kidney stone problems. There is a common (not entirely unfounded) belief that they are a problem associated with white, older adult males. However, according to a new study, cases of kidney stones are increasing in the United States, particularly among adolescents, females and African Americans.
Urine contains dissolved waste salts and minerals and, normally, these are flushed out of the body without a problem. However, if there is a significant enough increase in the level of these byproducts or a decrease in the amount of water in the system, as they pass through the kidney, they can start to form crystal deposits. These formations may be small at first but, as they grow, they cause serious problems. The stones may be passed out in urine while still small but if they become lodged in the urinary duct — or ureter — the flow between the kidney and the bladder is blocked causing back or stomach pain, nausea or fever as well as urine that is cloudy, foul-smelling or which has blood in it.
"The emergence of kidney stones in children is particularly worrisome, because there is limited evidence on how to best treat children for this condition," says Dr. Gregory E. Tasian, study leader and pediatric urologist and epidemiologist at The Children's Hospital of Philadelphia (CHOP). "The fact that stones were once rare and are now increasingly common could contribute to the inappropriate use of diagnostic tests such as CT scans for children with kidney stones, since health care providers historically have not been accustomed to evaluating and treating children with kidney stones."
Although researchers, clinicians and other public health experts have been aware of the overall increase in the number of kidney stones occurring in children and adolescents, this study provides a clearer idea of which specific groups of patients are most at risk. By analyzing state medical records and the age, race and sex characteristics of children and adults in South Carolina over a 16-year period — from 1997 to 2012 — the team collated data from nearly 153,000 child and adult kidney stone patients from a total population of 4.6 million.
Overall, the annually recorded number of kidney stones was up 16% during this 15-year period. The greatest rates of increase were among adolescents (up 4.7% per year), females (up 3% per year) and African Americans (up 2.9% per year). By 2012, the risk of kidney stones during childhood had doubled for both boys and girls. The highest rate of increase was among adolescent females and the risk for women of developing them over a lifetime, rose by 45%. For the ages 10 to 24, stones were more common among females while after 25, they more commonly affected among men. Among African Americans, the incidence of kidney stones increased 15% more than it did in whites for each five-year period of the study.
The rise in cases of kidney stones, the authors say, may be down to many factors including changes in dietary habits and people not drinking enough water. This can lead to an increase in sodium and a decrease in calcium in the diet — though the researchers admit dietary changes were not part of their study. In addition, in 2014 Tasian conducted a study that showed a link between higher daily temperatures and an increase in patients seeking treatment for kidney stones in five U.S. cities — increases in environmental temperature are already known to be linked to greater risk of kidney stones — so the increase of cases could even be a result of climate change.
"These trends of increased frequency of kidney stones among adolescents, particularly females, are also concerning when you consider that kidney stones are associated with a higher risk of chronic kidney disease, cardiovascular and bone disease, particularly among young women," Tasian says. Age, sex and race differences that the team found among kidney stone patients will require further study, says Tasian, but it is hoped the study will help health providers design targeted prevention strategies for people at higher risk for the condition. The research was published online in the Clinical Journal of the American Society of Nephrology.