Kidney Stone Treatment: Is More Always Better? The Volume-Outcome Link
"New research suggests a critical number of annual procedures could significantly improve patient outcomes in ureterorenoscopic stone treatment."
Kidney stones are a prevalent health issue, with cases on the rise globally. Ureterorenoscopy (URS), a minimally invasive procedure, is a common treatment. However, with the increasing use of URS, it's essential to understand what factors contribute to its success. Is it simply the technology, or does the experience of the medical team play a more significant role?
In various medical fields, the idea that higher procedure volumes lead to better patient outcomes is well-established. But what about URS? A recent study from Germany, the BUSTER-Trial, sheds light on this question. It explores the relationship between a hospital's URS volume and patient outcomes, seeking to define a threshold for optimal results.
This article breaks down the BUSTER-Trial findings, explaining how hospital volume affects stone-free rates and complication occurrences. Whether you're a patient exploring treatment options or someone simply curious about healthcare quality, understanding the volume-outcome link is crucial.
Why Treatment Volume Matters
Kidney stone disease can impose a substantial clinical burden, but its effects vary with stone characteristics, symptoms, patient health, and treatment choice. The relationship between the number of procedures performed and patient outcomes is therefore best viewed as an association that requires careful interpretation. More treatment volume may support experience and consistency in some settings, but it does not automatically mean that every patient will have a better result.
Guideline-Based Treatment
The AUA and EAU guidelines address evaluation and treatment for kidney and ureteral stones, including surgical options such as shockwave lithotripsy (SWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PCNL). Both guidelines strongly recommend open or laparoscopic stone removal only when SWL, URS, and PCNL are unlikely to offer a reasonable chance of success or are more likely to fail. The AUA also states that, because randomized controlled trials do not establish which laboratory tests should routinely be obtained before upper-tract stone surgery, testing should be selected according to procedural risk and medical history.
From Ancient Surgery to Stone Volume
Kidney stone disease has affected humans for thousands of years, and treatment has evolved from painful, high-risk ancient operations to minimally invasive laser procedures. More recently, stone volume has been introduced as a way to estimate stone burden more comprehensively than a single linear measurement. A 2024 review summarized available methods for evaluating stone volume and its use in urolithiasis treatment.
The Magic Number: 99 URS Procedures Annually
The BUSTER-Trial, a prospective observational study, collected data from 307 patients undergoing URS across 14 German hospitals. Researchers looked at various factors, including stone-free rates (complete removal or fragments small enough to pass), complication rates, and the annual number of URS procedures performed at each hospital.
- Threshold Identified: Hospitals performing 99 or more URS procedures annually demonstrated significantly better outcomes.
- Higher Success Rate: In hospitals exceeding this threshold, 92.9% of patients achieved the desired outcome (stone-free or small residual fragments with minimal complications), compared to 78.2% in lower-volume hospitals.
- Adjusted Advantage: Even after accounting for patient-specific factors (age, sex, BMI), stone characteristics (size, location), and physician experience, a higher hospital volume independently increased the chance of a successful outcome.
Better Imaging, More Detailed Planning
Recent reviews emphasize the role of non-contrast CT in assessing symptomatic kidney stones. CT can provide information about stone volume, size, density, and anatomical relationships, which can support treatment planning. Current guideline reviews from the AUA and EAU likewise compare contemporary approaches to managing kidney stone disease.
More Is Not Automatically Better
A higher procedure count should not, by itself, be treated as proof of superior care. Outcomes can depend on stone features, patient risk, treatment selection, and the quality of follow-up, so volume alone may be an incomplete measure of performance. The available information supports a cautious interpretation rather than a universal rule that more treatment always produces better results.
Comparing Stone Burden and Procedures
A 2025 review found that measuring stone area in two dimensions or stone volume in three dimensions predicts stone-free status after treatment better than measuring stone diameter alone. Procedure selection is commonly framed around the stone's size, location, and density, with ESWL, URS/RIRS, and PCNL each fitting different clinical situations. In the published ASPIRE data, SURE showed superior stone clearance and residual stone-volume outcomes compared with URS, while safety profiles and secondary endpoints did not differ significantly.
What This Means for Patients
The BUSTER-Trial provides valuable insights for patients seeking kidney stone treatment. While it's crucial to remember that individual patient factors play a significant role, considering hospital volume could be another piece of the puzzle.
Volume as a More Complete Measure
Stone volume is increasingly presented as a more informative measure of stone burden than a single maximum diameter. One report evaluated whether program-estimated stone volume could improve predictions of spontaneous passage compared with program-estimated and manually measured maximal diameter. A clinical review reports that stone volume has outperformed linear measurements in predicting stone-related follow-up events, spontaneous passage during conservative management, and stone-free rates after SWL and URS.
Tracking Practice at Scale
A retrospective study examined kidney stone prevalence and surgical-management trends over the past decade in both US commercial and Medicare claims data. These data can help describe how frequently stone procedures are performed and how practice patterns change across populations. At the procedural front, Urology Times reports that suction has moved from an aspirational concept to a core component of modern ureteroscopy, suggesting continued evolution in stone surgery.
A Changing Treatment Landscape
Recent discussions of ureteroscopic stone treatment have brought international experts together to examine advances and ongoing challenges in the field. Contemporary reviews also address the epidemiological determinants of kidney stone disease alongside updated management approaches. Other recent work considers stone types, corresponding treatment strategies, and emerging concerns, underscoring that technical progress must be matched with broader clinical and system-level evaluation.
Patient-Centered Outcomes
For patients, the value of a high-volume treatment setting ultimately depends on whether it delivers appropriate care, effective stone clearance, and acceptable safety. Procedure counts alone cannot capture individual differences in stone burden, anatomy, medical history, or recovery. A balanced assessment therefore considers both institutional experience and the patient's specific treatment needs.
It's important to have an open discussion with your urologist about their experience and the resources available at the hospital or clinic. Don't hesitate to ask about the number of URS procedures they perform annually and what protocols they have in place to ensure patient safety and optimal outcomes.
Ultimately, the best treatment decision is a collaborative one, made with a qualified medical professional who understands your individual needs and circumstances. While higher volume may suggest a greater likelihood of success, a skilled surgeon in a lower-volume setting can still deliver excellent care.