Experts already know that our microbiomes — or the colonies of microorganisms that occur naturally in our bodies — are affected by antibiotics.
And, it is also worth noting that changes to the intestines' microbiome have previously been linked with increased risk of kidney stones.
But, for the first time, research published in the Journal of the American Society of Nephrology pinpoints a link between antibiotics and kidney stones.
Kidney stones are pebble-like mineral deposits that can form in either or both of the kidneys.
The stones do not usually cause significant damage but can be very painful if they are too large to be passed easily through the urinary tract. In such cases, a urologist may need to remove the kidney stones or break them into smaller pieces.
In the United States, around 11 percent of men and 6 percent of women will have kidney stones at least once during their lifetime.
However, the authors of the new study note that the prevalence of kidney stones has risen by 70 percent in the past 3 decades — particularly among adolescents and young women.
"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."
Study co-author Michelle Denburg
'Twice as likely' to develop kidney stones
The scientists analyzed the electronic health records of 13 million adults and children in the United Kingdom who saw their doctor between 1994 and 2015.
The data included the treatment history of 26,000 individuals with kidney stones, which the team compared with the health records of almost 260,000 people who had not developed kidney stones (the controls).
The analysis found that several types of oral antibiotic — more specifically, sulfas, cephalosporins, fluoroquinolones, nitrofurantoin, and broad-spectrum penicillins — were linked with an increased risk of kidney stones.
Even after controlling for factors such as "age, race, sex, urinary tract infection, other medications, and other medical conditions," the increased risk remained significant.
Those who received sulfa antibiotics were twice as likely as people in the control group to develop kidney stones, while individuals who received broad-spectrum penicillins were 27 percent more likely. The association was found to be strongest among children and adolescents.
This increased risk of kidney stones remained high even several years after the participants were exposed to antibiotics, but the researchers did find that the risk decreased over time.
Doctors should be cautious
The study authors highlight that, in other studies, up to 30 percent of antibiotic prescriptions have been found to be inappropriate.
They believe that their findings should inform doctors' decisions when considering whether or not to prescribe antibiotics to children, as they are the greatest recipients of these drugs.
"Our findings suggest that antibiotic prescription practices represent a modifiable risk factor," explains lead investigator Dr. Gregory E. Tasian. "A change in prescribing patterns might decrease the current epidemic of kidney stones in children."
The scientists are now expanding their research into broader studies as part of a wider effort to understand how changes to the microbiome affect the risk of developing kidney stones.