Safety and Efficacy of Antegrade Flexible Ureteroscopy-Assisted Percutaneous Nephrolithotomy for Staghorn Calculi: A Prospective Multicenter Clinical Study

Background Renal calculi are among the most common diseases in urology. Current treatment options include extracorporeal shock wave lithotripsy (ESWL), flexible ureteroscopic lithotripsy, and percutaneous nephrolithotomy (PCNL). For renal stones ≥2 cm, PCNL is the recommended first-line treatment.

However, because of the large stone burden and the involvement of multiple calyces, it is often difficult to achieve complete clearance with a single PCNL session. Excessive angulation of the nephroscope may increase the risk of infundibular tears and bleeding, and stones located in parallel or narrow infundibula may be difficult to access, reducing the one-stage stone-free rate. To improve outcomes, several strategies have been adopted:

Multiple percutaneous tracts: Establishing additional tracts allows access to calyces unreachable from the primary tract and increases stone-free rates. However, this also increases the risks of bleeding, infection, and injury to the kidney or adjacent organs. In addition, expansion of the first tract may cause perirenal hematoma or morphological changes due to urine extravasation, making subsequent punctures more challenging. Multiple tracts also prolong postoperative recovery and increase hospitalization costs. Staged procedures: The first PCNL session removes stones in the renal pelvis and accessible calyces, while residual stones are addressed in a second-stage retrograde ureteroscopy. This reduces the risks compared with multiple tracts, but prolongs the treatment cycle and increases costs. Endoscopic combined intrarenal surgery (ECIRS) with modified patient positions: Positions such as the modified supine split-leg, lateral decubitus, or female-specific "Galdakao-modified supine Valdivia" allow simultaneous use of ureteroscopic and percutaneous approaches. This combines the efficiency of PCNL with the wide access angle of ureteroscopy, reduces the need for repositioning under anesthesia, and facilitates intraoperative monitoring. However, it requires two surgical teams, duplicate equipment, and high coordination, which may prolong operative time.

Previous studies suggest that combining single-tract PCNL with flexible ureteroscopy and holmium laser lithotripsy may be an ideal approach for staghorn stones. While antegrade cystoscopic lithotripsy accommodates thicker fibers and offers faster irrigation and clearer visualization, the larger diameter of the cystoscope limits its passage through the ureter, risking residual fragments. Recently, antegrade flexible ureteroscopy-assisted PCNL has been attempted, but most studies are small retrospective series or case reports. The limited adoption may be due to the high purchase and repair costs of reusable flexible ureteroscopes. The development of single-use ureteroscopes has largely overcome these barriers, providing a foundation for multicenter prospective studies.

Based on this background, a multicenter clinical study of antegrade flexible ureteroscopy-assisted PCNL for staghorn calculi has important clinical value. Our preliminary work showed that when the number of stone branches was ≥5, the need for multiple tracts and staged procedures increased, while operative time was prolonged, hospital stay was longer, and the stone-free rate was reduced. We therefore further compared the efficacy of standard PCNL and antegrade flexible ureteroscopy-assisted PCNL stratified by stone branch number.