Oral antibiotics tied to increased risk of kidney stones

Children and adults who take five commonly prescribed types of antibiotics may be more likely to develop kidney stones than people who don’t use these medicines, a recent study suggests.

Researchers examined electronic health records collected from 1994 to 2015 for 25,981 people who developed kidney stones and a control group of 259,797 similar individuals who did not. Using the kidney stone diagnosis as an “index date,” researchers then looked for prior antibiotic prescriptions in both groups.

Exposure three to 12 months before the index date to any of five antibiotics - sulfas, cephalosporins, fluoroquinolones, nitrofurantoin/methenamine, and broad-spectrum penicillins - was associated with an increased risk of kidney stones.

The risk increase associated with these antibiotics ranged from 27 percent higher odds with broad-spectrum penicillins to more than doubled odds with sulfas.

“Without a doubt, antibiotics have saved millions of lives and are needed to prevent death and serious harm from infections; the benefits outweigh the potential harms,” said lead study author Dr. Gregory Tasian of the Children’s Hospital of Philadelphia.

“These results don’t suggest that antibiotics should not be prescribed when indicated,” Tasian said by email. “However, they do support antibiotic stewardship - the judicious and appropriate use of antibiotics and reducing inappropriate use of antibiotics for a viral illness.”

Scientists already knew that antibiotics alter the composition of the human microbiome - all of the bacteria, viruses and fungi that live in and on the body.

Changes in the intestinal and urinary microbiome have also been linked to kidney stones, but no previous studies revealed an association between antibiotics and stones, researchers note in the Journal of the American Society of Nephrology.

The strongest risks for kidney stones were in children and adolescents, the study found. The risk of kidney stones decreased over time but remained elevated several years after antibiotic use.

Not all antibiotics were associated with an increased risk of kidney stones, however. The study examined 12 types of antibiotics, and found seven that didn’t appear to influence the risk of kidney stones.

The study wasn’t a controlled experiment designed to prove whether or how antibiotics might cause kidney stones. Another limitation is that some people might have had undiagnosed kidney issues before they took antibiotics, potentially inflating the risk associated with antibiotics.

Kidney stones can also take years to develop, and affect only about 10 percent of people, making it challenging to prove a direct link to antibiotics that most people will take at some point in their lives, said Jeremy Burton a researcher at the University of Western Ontario and deputy director of the Canadian Centre for Human Microbiome and Probiotics, Lawson Health Research Institute in London, Ontario.

“Kidney stone disease rates have been increasing steadily for no apparent reason, and many theories have been postulated. These range from global warming resulting in decreased hydration, to the microbiome changing due to an unhealthy Western diet,” Burton, who wasn’t involved in the study, said by email.

“It is important to note that even with these enormous samples sizes (in the study) some confounding factors may remain, such as antibiotic use for the treatment of a urinary tract infection, a condition associated with kidney stones,” Burton added. “Nonetheless these data suggest that there is a risk associated with certain antibiotic use and kidney stones.”