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Kidney stones are painful and they are more prevalent than they were decades ago. 

While it’s difficult to definitively prove risk factors for the development of these hard, stone-like pieces in the urinary tract, researchers have identified one possible culprit: oral antibiotics.

A team from Children’s Hospital of Philadelphia analyzed electronic records from 13 million adults and children seen by doctors in the United Kingdom between 1994 and 2015.

They concluded that when patients had taken certain oral antibiotics, they had a significantly higher risk of developing kidney stones.

The risk was highest for younger patients, particularly young women.

Healthline interviewed the primary author of the study and an outside expert. Both concluded that, although more research is needed to form a more conclusive link, the study shines a light on the overprescription of antibiotics.

“When I was in residency, kidney stone disease was something that happened primarily among middle-aged white men,” Dr. Gregory E. Tasian, MSCE, a pediatric urologist at Children’s Hospital of Philadelphia and lead study author, told Heathline.

“Then, over the last 30 years, we’ve seen this dramatic shift in the epidemiology, where there’s a tremendous increase in the number of children and adolescents who are affected by stones,” he added. “So the disease, which is still the same, is now beginning earlier in life.”

Searching for a reason

Tasian said that medical wisdom has attributed the increased prevalence of kidney stones to changing diets — something that he believes to be part of the explanation but likely not the driving factor.

With this in mind, Children’s Hospital of Philadelphia researchers looked at prior studies that examined the microbiome — the community of organisms in the gut and urinary tract.

They identified differences in patients who developed kidney stones and those who didn’t. Given that antibiotics are known to create shifts in the microbiome, they saw a connection.

Dr. Hiren Patel, chief of nephrology at Nationwide Children’s Hospital in Ohio, told Healthline that the paper shines a light on some interesting possible connections.

“There may be a connection between obesity and kidney stones,” he said. “Interestingly, the paper talks about how, if antibiotics affect the gut microbiome, then that might be a risk factor for kidney stone formation. There’s also some potential connection between gut microbiome and obesity, too, so maybe there’s a potential connection for all three factors.”

In the study, Tasian and his co-authors note that the overall prevalence of kidney stones has gone up by 70 percent over the previous three decades.

They also state that about 30 percent of antibiotics prescribed in office visits are unnecessary, adding that children receive more antibiotics than other age groups.

“There’s definite data that the incidence of kidney stones has been increasing over the last several years, and antibiotic use has also been increasing,” said Patel. “We also know that even though antibiotic use is increasing, that a lot of the times, the reason for it is inappropriate. So this is one additional thing to think about when trying to decide if someone should be on antibiotics.”

“The common scenario is that an antibiotic is prescribed for a viral infection that it’s just not going to be effective for, something the body has to clear on its own,” said Patel. “In that case, an antibiotic is being prescribed and a patient is taking it, but it’s probably not having much benefit — and yet, there may be some risk to it.”

Patel says that upper respiratory infections are probably the most common ailments in which antibiotics are unnecessarily prescribed.

Antibiotics effective but overprescribed

Tasian makes it clear that this study is not advocating against antibiotics in general.

“In no way are we suggesting that antibiotics should not be used, or should not be prescribed when clinically indicated,” he said. “But there’s a substantial proportion of antibiotics that are prescribed unnecessarily. For example, for viral illnesses that do not need antimicrobial therapy. So I think these findings should give us pause, to make sure that we’re prescribing antibiotics judiciously and appropriately.”

“It’s an interesting, novel finding that raises some questions and needs some additional research to try to clarify,” concluded Patel.

Tasian says that, while the research helps establish a link between certain oral antibiotics and the risk of developing kidney stones, his team is continuing to study the specifics of this link.

“I think this paper helped us answer the ‘what,’ but it doesn’t answer the ‘how’ or the ‘why,’” he said. “So we need to investigate some of the causal mechanisms behind these associations. Our group is currently in the final stages of a study that is examining the community of organisms in the gut that may be different between those children and adolescents that form stones versus those that don’t — and also identifying the metabolic signature, the metabolites that these bacteria produce, that may help explain why antibiotics increase the risk of stones and how they do that.”