Bacteria Found Within Kidney Stones, Challenging Long-Held Assumptions

For centuries, kidney stones have been understood as mineral formations arising from chemical and physical processes within the urinary system. Yet, a recent breakthrough study reveals a previously unknown component in the most common type of kidney stone: bacteria. This discovery challenges the long-held belief that these stones are entirely abiotic and opens new avenues for prevention, and treatment.

What the Study Found

Researchers at the University of California Los Angeles (UCLA) discovered live bacteria and biofilms inside calcium oxalate kidney stones, which account for nearly 80 percent of all cases. This finding suggests that bacteria may not only be present in these stones but may actively contribute to their formation. The study, published in the peer-reviewed journal PNAS, utilized electron and fluorescence microscopy to identify bacterial components embedded within the crystal structure of the stones.

“This breakthrough challenges the long‑held assumption that these stones develop solely through chemical and physical processes, and instead shows that bacteria can reside inside stones and may actively contribute to their formation,” says Dr. Kymora Scotland, an assistant professor of urology at the David Geffen School of Medicine at UCLA and the study’s co-senior author. “By uncovering this novel mechanism, the study opens the door to new therapeutic strategies that target the microbial environment of kidney stones.”

The Role of Bacteria in Kidney Stone Formation

While bacteria are known to contribute to the formation of struvite kidney stones (a rarer type, accounting for 2-6 percent of cases), their presence in calcium oxalate stones was previously unexpected. The researchers propose that bacteria may facilitate seed the initial formation of kidney stones, becoming trapped within the growing crystal structure. This suggests that kidney stones should be considered an “organic–inorganic biocomposite,” where bacterial biofilms are a key component.

Implications for Treatment and Prevention

This discovery has significant implications for how kidney stones are treated and prevented. Understanding the role of bacteria could lead to new therapies that target the microbial environment within the stones. It may also help explain the connection between recurrent urinary tract infections and recurrent kidney stone formation.

The researchers are currently conducting further studies to determine how bacteria and calcium-based kidney stones interact and to identify which bacterial species are most involved in stone formation. They aim to understand why some individuals are more susceptible to recurrent stone formation and to develop more effective prevention strategies.

Understanding Kidney Stones

Kidney stones are composed of clumps of small crystals that form when certain substances in urine become highly concentrated. About 1 in 11 people will develop kidney stones in their lifetime. Risk factors include family history, metabolic syndrome, and inadequate fluid intake. While kidney stones can cause excruciating pain, they are typically not dangerous if treated promptly, but can lead to serious complications without appropriate medical care.

Further research is needed to fully elucidate the role of bacteria in the formation of all types of kidney stones, but this discovery represents a significant step forward in our understanding of this common and often painful condition.