New Research Shows Bacteria May Help Kidney Stones Form

A kidney stone is a hard, pebble-like piece of material that forms in the kidneys when certain minerals in urine stick together and crystallize.

Kidney stones can be as small as a grain of sand or as large as a golf ball. Smaller stones may pass on their own, but larger stones may get stuck and require medical intervention. 

Visit NKF’s Kidney Stone Hub to learn more. 

Kidney stone symptoms often begin when a stone moves or blocks urine flow.

The most common signs include:

• Sharp pain in your side, back, or lower belly
• Pain that comes in waves and can move toward the groin
• Blood in the urine (pink, red, or brown urine)
• Burning or pain when urinating
• Frequent urge to urinate
• Nausea or vomiting
• Fever and chills

It’s very important to go to the emergency room if you begin experiencing any of these symptoms.  

A major NIH-funded study published in January 2026 found that bacteria are present in many kidney stones, including some previously thought not to have bacteria.

Key findings include: 

• Bacteria were found in both struvite stones and calcium stones
• Some calcium stones, previously believed to have no bacteria, contained microbes
• Bacteria were found both inside the stones and on their surface
• These bacteria formed biofilms or protective communities of microbes
• Nearly half of the stones from people without urinary tract infections still contained bacteria

In simple terms, bacteria may not just be there. They may help stones form.

This discovery challenges a long-held belief that most kidney stones form just from chemical buildup in urine.

Instead, researchers now believe:

• Some kidney stones may have a biological (not just chemical) cause
• Bacteria may act as “building blocks” for kidney stones
• Biofilms may create a surface where minerals can stick and grow

Researchers say this information could lead to new treatments that:

• Prevent stones from forming
• Target bacterial biofilms
• Reduce kidney stone recurrence

Learn more about kidney stone treatments. 

While research continues, there are still important steps you can take today:

• Drink enough fluids each day
• Follow your care team’s advice if you’ve had stones before
• Talk to your doctor if you notice symptoms early
• Ask about your personal risk for recurrence

Get a kidney stone diet and prevention plan.