Kidney stones on the rise in South Carolina children

Kidney stones can be excruciating no matter what your age and while they are rare in children, a new study shows they increased four-fold among South Carolina kids between 1996 and 2007.

"The trend is concerning," Dr. David J. Sas, a pediatric kidney specialist at the Medical University of South Carolina, told Reuters Health.

Sas and colleagues combed state hospital emergency department data for the diagnosis of kidney stones in children from birth to age 18.

They found that the number of cases per 100,000 children climbed from 7.9 to 18.5 over the 12 years of the study. In all, 1,535 children were diagnosed with the painful disease. The greatest increase occurred among white adolescents between the ages of 14 and 18, according to a report in the Journal of Pediatrics.

Running contrary to the gender breakdown of kidney stone formation in adults, the increase in stone formation among South Carolina girls was particularly intriguing to the researchers.

"In the 90s, the rate of stone formation was the same between boys and girls. However, over the last decade and a half, the girls have outpaced the boys and are now about 50 percent more likely to form stones than boys," Sas said.

The South Carolina study is the "largest investigation to date of pediatric stone formation" but does not try to answer why stone formation is on the rise among the state's children.

Sas said pinning down a cause to the increase is hard to do but there are several suspects: obesity, too much salt and too little milk in the diet, and changes in antibiotic use.

While obesity among South Carolina children has gone up along with the incidence of kidney stones, Sas says anecdotal evidence from his own practice would argue against obesity as the major cause.

"In my clinic, most of the stone formers are pretty fit kids," he said.

To much salt in the diet is a more likely suspect. Roughly 92 percent of American kids have "excessive sodium intake," Sas and colleagues point out. In adults, excess sodium is associated with stone formation.

Another suspect is a drop in milk consumption because lower calcium consumption is thought to up the risk of stone formation.

Sas said there is some interest in studying the effect of antibiotic use on stone formation. It's hypothesized that over-use of antibiotics may kill normal bacteria of the gut that consume minerals that can form kidney stones.

While the current study only looked at South Carolina data, the state is part of what's called the "stone belt," an area of the country with high adult kidney stone rates stretching roughly from Virginia to Florida to Texas. Sas believes the current results may be reflected throughout the stone belt and possibly the rest of the United States, which adds to the urgency of more research.