From Physics to Treatment: How Fundamental Research Improves Kidney Stone Care

Every year, more than half a million people in the United States are rushed to the emergency room because of kidney stones. About 10% of people will experience the disease at least once in their life, driving more than $2 billion in annual healthcare costs — and many patients, including mothers, report that the pain rivals that of childbirth. 

Treatments for this common condition have improved dramatically over the past few decades. But before new procedures become widely used in the operating room, they are shaped by fundamental research carried out in academic labs — like that of Pei Zhong, a professor in Duke’s Department of Mechanical Engineering & Materials Science. 

Zhong first encountered kidney stone treatment, or lithotripsy, while attending graduate school at the University of Texas Southwestern Medical Center in the early 1990s. At the time, shockwave lithotripsy — a technique that uses acoustic shockwaves to break stones from outside the body — had just been approved by the FDA. By focusing shockwaves on a kidney stone, doctors could fracture it into pieces small enough to be extracted or passed naturally. 

“All of a sudden, you don’t have to perform open surgery to remove the stone: Patients can be treated noninvasively,” Zhong recalled. The medical community was thrilled by this noninvasive technique, but this enthusiasm came with uncertainty. Manufacturers provided recommended ranges for lithotripter machine settings such as power level and pulse repetition rate. But in the clinic, doctors had to make their own calls for how to adjust these settings if outcomes weren’t as expected. Even more basic questions remained unanswered: How exactly did shockwaves break stones? And what damage might they cause to surrounding tissue? 

Those unanswered questions became the focus of Zhong’s research. Over the past several decades, his work has investigated the acoustic and mechanical physics underlying shockwave lithotripsy, helping clarify how stones fracture and how tissue injuries occur. One interesting insight from this work was the role of cavitation bubbles, or tiny vapor pockets that rapidly form and collapse under extreme pressure changes caused by the shockwaves. These bubbles, Zhong’s lab showed, play a key role alongside the shockwaves to help break stones apart.   

Many of Zhong’s discoveries have had practical applications in the medical device industry. Some of his findings informed design improvements in commercial lithotripters produced by the technology company Siemens. Others revealed that gradually increasing shockwave energy during treatment can protect patients while still effectively breaking stones — a technique that then was adapted in clinical practice. Zhong is also involved in a new lithotripter design being developed under a North Carolina Biotechnology Center Translational Research Grant, and is listed as co‑inventor on 10 patents related to shockwave lithotripsy technologies. 

“I was drawn to this research not only because it’s rich with engineering challenges, but also because it has immediate and profound clinical impact,” Zhong said. “Sure, every time we publish an important finding, it adds a nice paper to the lab profile. But more importantly, it helps doctors better understand both the safety limits and optimal performance settings of the technology in their hands, leading to better patient care.” 

That translational mindset has remained central to Zhong’s research, even as kidney stone treatment has evolved. Over the last two decades, some clinicians have been transitioning from shockwave lithotripsy to laser lithotripsy. In this newer approach, doctors insert a thin tube with a tiny camera and laser fiber into the kidney and directly blast the stone. Although laser lithotripsy is more invasive, it allows physicians to more effectively monitor and remove stone fragments, reducing the likelihood that leftover pieces will seed future stones.

Zhong’s lab has applied the same fundamental‑science approach to laser lithotripsy. They have studied how laser parameters — such as pulse energy, power and repetition rate  — could be adjusted to retain stone-breaking efficiency while minimizing thermal damage to tissue. In their latest paper published in Advanced Science in February 2026, the team also reported an interesting finding: Cavitation bubbles play a more crucial role in laser lithotripsy than initially thought. 

One persistent challenge in laser procedures is retropulsion, or the tendency for stones to fly backwards when struck by the laser. This forces doctors to “chase” after the stone, extending procedure time. For years, retropulsion was thought to result mainly from the recoil of laser hitting stone, along with the associated vapors and debris ejection.

Using high‑speed imaging at millions of frames per second, Zhong’s team discovered a different story. When the fluid immediately surrounding the laser is vaporized by the laser’s heat, tiny cavitation bubbles form and collapse asymmetrically in donut-shaped swirls, sometimes pushing stones away and sometimes pulling them closer. These bubble dynamics, the researchers found, are major drivers of retropulsion. If clinicians can learn to control these bubbles and their behavior, they may be able to keep stones within optimal reach. 

Obed Isaac, a postdoctoral associate in Zhong’s lab and one of the paper’s authors, sees this as part of a larger theme in his work. “I’ve always been interested in how phenomena like cavitation bubbles — something you can barely see with the naked eye — can be incredibly destructive,” he said. “What excites me here is using that same physics to actually help people.” 

Even small improvements have compounded effects. As Arpit Mishra, another Zhong lab postdoc associate and author on the paper, explained: “Every millimeter of stone movement adds minutes in the operating room. Over a day, those minutes add up — so saving even a little time per procedure can mean one more patient gets treated on the same day.” 

The work doesn’t stop there. Inspired by their latest findings, Isaac, Mishra and others in Zhong’s group are now exploring ways to manipulate cavitation bubble behavior. Given Zhong’s track record with informing shockwave lithotripter design, it’s likely that the lab’s next discoveries will help directly shape future laser lithotripsy technologies. 

Supported continuously for 29 years by federal funding agencies such as the National Institutes of Health, this kind of fundamental research continues to quietly influence how medicine is practiced. 

“From fundamental research we gain new knowledge, insights and inspirations for technology innovation and optimized treatment strategy,” Zhong said. “And from that, we can improve clinical tools to make treatments safer and more efficient for millions of patients worldwide.”