Retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PCNL) are two key minimally invasive treatments for kidney stones in both adults and children. The success of these procedures is primarily measured by two factors: (1) the absence of complications and (2) the stone-free rate (SFR), which is defined as the absence of residual fragments (RFs) larger than 4mm, as outlined by international guidelines. According to the European Association of Urology, RFs larger than 4mm should be addressed with endoscopic treatment or shockwave lithotripsy due to their low chances of passing naturally and their high likelihood of requiring further intervention. A systematic review and meta-analysis revealed that 30% of patients with RFs or dust particles smaller than 4mm experienced symptoms or required intervention within three years, while another 30% saw spontaneous passage within two years. However, there is still no consensus on the definition of RFs, with studies varying in their criteria for what is considered clinically insignificant. For instance, RFs measuring less than 2mm after RIRS and less than 4mm after PCNL are often regarded as insignificant. A more stringent measure, the zero-fragment rate (ZFR), was introduced by Schoenthaler et al. and applied in a study by Ulvik et al., which evaluated different laser sources for RIRS. ZFR, which refers to the complete absence of RFs larger than 1mm, is becoming a practical goal for stone surgery. Technological advancements like smaller ureteroscopes and aspiration devices have improved outcomes, moving closer to ZFR while reducing complications. Preoperative measurement of stone volume (SV) and precise postoperative evaluation of RFs through three-dimensional imaging are crucial for improving outcomes in RIRS and PCNL. These advanced measures, including volume-based stone-free rates (V-SFR), offer a more accurate approach to predicting surgical success and preventing stone regrowth or recurrence.
Rethinking stone-free rates and surgical outcomes in endourology
Reviewed by Asif H Ansari
Rethinking stone-free rates and surgical outcomes in endourology: a point of view from PEARLS members.
