Traditionally, the size of a kidney stone has been the primary determinant for selecting a treatment method. However, a significant shift is underway towards ‘patient-centered treatment selection,’ which now considers not only stone size but also its location, number, anatomical structure, and the patient’s recovery burden.
The introduction of advanced suction technologies like FANS (Flexible and Navigable Suction Ureteral Access Sheath) and robotic flexible ureteroscopy is further expanding the scope of endoscopic kidney stone surgery (RIRS).
Dr. Joon Chae Na of Goldman Urology Clinic, Jamsil Branch, recently delivered a compelling lecture at the ‘2026 KSER Academic Festival’ Sub-plenary Session in Busan. His presentation, titled ‘RIRS vs mPCNL for Intermediate Stones (1.5–2.5 cm): What Do Patients Actually Prefer?’, explored the advantages and disadvantages of Retrograde Intrarenal Surgery (RIRS) and Mini Percutaneous Nephrolithotomy (mPCNL) for intermediate-sized kidney stones, emphasizing the crucial role of patient preference and quality of life in treatment decisions.
Generally, the necessity for Percutaneous Nephrolithotomy (PCNL) increases with larger kidney stones. Guidelines from the European Association of Urology (EAU) and the American Urological Association (AUA) actively recommend PCNL for kidney stones exceeding 20mm. Yet, for intermediate stones ranging from 1.5 to 2.5 cm, the choice between RIRS and PCNL often overlaps, making it challenging to definitively recommend one method based solely on size.
Even a 2cm stone can present varying treatment difficulties depending on whether it is located in the renal pelvis, the lower pole of the kidney, or spread across multiple calyces.
For intermediate-sized kidney stones (1.5-2.5 cm), which surgical approach is better: RIRS or PCNL?
Both surgical methods possess distinct advantages and disadvantages. A 2023 Cochrane review, cited by Dr. Na in his presentation, indicated that PCNL generally achieves a higher stone-free rate and reduces the likelihood of additional treatments compared to RIRS, a difference particularly pronounced for stones larger than 2cm. Conversely, RIRS typically results in shorter hospital stays, with previous studies reporting less post-operative pain and bleeding, leading to a comparatively easier recovery process.
Ultimately, the medical team’s priority of effective stone removal does not always align with the patient’s perceived burden. While clinicians consider stone clearance rates, re-treatment potential, and technical surgical difficulty, patients often prioritize factors such as pain, bleeding, the discomfort of tube insertion, recovery time, and their swift return to daily activities.
Case studies presented by Dr. Na illustrate these differing priorities. In one instance, a patient with a 23mm lower pole stone and a 7mm ureteropelvic junction stone was recommended PCNL, but ultimately chose RIRS to minimize surgical risk and invasiveness. Conversely, another patient, for whom RIRS was recommended, opted for PCNL to ensure the most effective removal of a lower pole stone.
This highlights that while stone size and location are initial considerations, the final treatment choice must also integrate the patient’s personal values and what they deem most important.
Recent technological advancements are also blurring the lines of these treatment choices. Specifically, techniques like FANS, which aspirates stone fragments during RIRS, are addressing the historical limitation of RIRS regarding stone removal efficiency.
Dr. Na explained that while FANS did not initially create the shift for RIRS in 15-25mm stones, its introduction has expanded the clinical boundaries. This allows RIRS to be considered for larger and more complex stones that were previously only candidates for PCNL. This signifies a move away from simple stone size as the sole differentiator between RIRS and PCNL, towards a more holistic consideration of patient anatomy, invasiveness, and recovery.
Ultimately, the choice between RIRS and PCNL for kidney stones is shifting from a purely size-based decision to a comprehensive assessment that prioritizes both clinical efficacy and patient well-being, with technological advancements like FANS further broadening RIRS applicability.
This evolution is further supported by a clinical study on the Zamenix robotic flexible ureteroscopy system, jointly conducted by Dr. Joon Chae Na and Dr. Min Seung-gi. The researchers analyzed 18 cases of upper urinary tract stone surgery performed with Zamenix between October 2025 and May 2026. The average stone size was 18.8mm, with 44.4% of cases involving stones larger than 20mm and 50% involving multiple stones (three or more). The study included stones as large as 35mm and up to 14 multiple stones.
No post-operative complications were observed in the 18 cases, though additional treatment was required in 5 cases (27.8%), and 2 cases (11.1%) necessitated conversion to a manual flexible ureteroscope. The research team confirmed the potential of the robotic system’s stable scope control, precise laser manipulation, and FANS-assisted stone removal for treating complex stones. They also noted that additional treatment or conversion to manual endoscopy might still be necessary depending on anatomical structures.
This does not imply that robotic systems or suction technologies will completely replace PCNL. Instead, they offer expanded treatment options for certain kidney stones that were previously challenging for RIRS. As reducing the patient’s burden during treatment becomes as crucial as achieving high stone clearance rates, the criteria for selecting surgical methods are evolving from technology-centric to patient-centric.
Dr. Joon Chae Na emphasized, “Kidney stone surgery is not about choosing between RIRS and PCNL based solely on stone size. It requires considering the stone’s location, number, anatomical structure, the likelihood of single-session clearance, and crucially, what factors the patient values most.” He added, “As clinical experience with new technologies like FANS and robotic endoscopy accumulates, the range of applicability for RIRS is changing. Therefore, it is vital to thoroughly explain the pros and cons of each treatment option and select the most appropriate one for the patient.”
Dr. Na concluded, “We will continue to accumulate real-world clinical data to verify how new technologies impact patient burden and outcomes, and to establish more rational treatment selection criteria for kidney stone patients through ongoing research.”