Children and adults treated with oral antibiotics may have a higher risk of developing kidney stones, according to a new study.

The findings, published in Journal of the American Society of Nephrology, suggested that the strongest risks appeared at younger ages and among patients most recently exposed to antibiotics. "The overall prevalence of kidney stones has risen by 70 per cent over the past 30 years, with particularly sharp increases among adolescents and young women," said lead author Gregory E. Tasian from the Children's Hospital of Philadelphia (CHOP). According to the researchers, kidney stones were previously rare in children.

"The reasons for the increase are unknown, but our findings suggest that oral antibiotics play a role, especially given that children are prescribed antibiotics at higher rates than adults," said co-author Michelle Denburg from CHOP. For the study, the team analysed prior antibiotic exposure for nearly 26,000 patients with kidney stones, compared to nearly 260,000 control subjects. They found that five classes of oral antibiotics -- oral sulfas, cephalosporins, fluoroquinolones, nitrofurantoin, and broad-spectrum penicillins -- were associated with a diagnosis of kidney stone disease.

After adjustments for age, sex, race, urinary tract infection, other medications and medical conditions, patients who received sulfa drugs were more than twice as likely as those not exposed to antibiotics to have kidney stones, the researchers said. For broad-spectrum penicillins, the increased risk was 27 per cent higher, the researchers added. They also mentioned that the risk of kidney stones decreased over time but remained elevated several years after antibiotic use. "Our findings suggest that antibiotic prescription practices represent a modifiable risk factor, a change in prescribing patterns might decrease the current epidemic of kidney stones in children," Tasian noted.