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Use of certain oral antibiotics may be linked to the growing incidence of kidney stone formation, according to a study recently published in the Journal of the American Society of Nephrology. Conducted by researchers at the Children’s Hospital of Philadelphia (CHOP), this study found that younger patients who were exposed to antibiotics were at the highest risk of developing kidney stones.

Using data from roughly 14 million children and adults in the United Kingdom, the team set out to determine what oral antibiotics could be associated with increased kidney stone risk. They found that exposure to any of five oral antibiotics 3-12 months prior to date of diagnosis was linked to an increased diagnosis of kidney stones, with the highest risk being within 3 to 6 months after antibiotic use. Sulfa drugs were found to cause the greatest increase in risk, with cephalosporins, fluoroquinolones, nitrofurantoin/methenamine, and broad-spectrum penicillins following in that order.

Lead author Dr. Gregory Tasian, MD, MSCE, claims that among the most prominent findings of the study was that “the younger the patient was, the greater the risk of stones”. Dr. Tasian notes that though this risk decreased over years after the antibiotic prescription, it remained present for as long as 5 years after antibiotic use.

He goes on to highlight the growing issue of kidney stones in youth. “Kidney stones have increased in prevalence by about 70% over the last 20 to 30 years. The greatest increase has been found among adolescents and young people. The reasons for that are not entirely known.”

What’s the Take-Home Message?

This study adds to the growing body of work against over-prescription of antibiotics. A study published in JAMA estimated that the antibiotic prescription rate from 2010-2011 was 506 for every 1000 patients, and that only 353 prescriptions were likely necessary.

kidney stones

Speaking on excessive antibiotic prescription, Dr. Tasian states that “30% of the time they’re not needed because they’re prescribed for a viral illness,” and that the findings of this study should caution practitioners to ensure that antibiotics are the correct course of treatment for their patients prior to writing a prescription.

For patients with a history of kidney stones, this study may suggest avoidance of these five classes of antibiotics. Dr. Tasian asserts that “symptomatic episodes” in kidney stone patients are often recurrent. He acknowledges the lack of research into antibiotics’ effects on recurrent stones but concludes that, “if there is an alternative antibiotic that could be used that was not associated with stones, that may be a good choice to make.”

What’s the link?

No causal relationship between antibiotics and kidney stones was able to be investigated due to the lack of information such as urine chemistry, stone composition, and microbiome makeup, however Dr. Tasian believes that modification of the microbiome is a likely candidate. “I think the urinary microbiome and the intestinal microbiome are the most likely sites in which antibiotics are acting by changing the composition of the microbiome,” he claims. An alternative theory is that the direct crystallization of antibiotics is causing these stones, however Dr. Tasian notes that this has not been observed to the “magnitude of risk” seen in the study.

kidney stones

Going Forward

The team of researchers is currently conducting a study to evaluate the relationship between microbiome composition and stone formations, comparing 45 patients with kidney stones to age, race, and sex matched controls with no stones present and analyzing microbiome composition in both groups. Dr. Tasian claims the team is “trying to understand what differences exist both at the broad level such as the diversity of the types of bacteria in there, and also the specific types of bacteria within the intestinal tract in these patients.”

Sources: JASN, CHOP