Flexible and Navigable Access Sheath (FANS) VS Direct in Scope Suction (DISS) in Treatment of Renal Stone > 2 cm , Controlled Randomized Trial

Retrograde intrarenal surgery (RIRS) has revolutionized the management of renal stones, yet achieving high stone-free rates (SFR) while maintaining low intrarenal pressure (IRP) remains a challenge. Elevated IRP during irrigation is linked to post-operative complications, including systemic inflammatory response syndrome and renal parenchymal damage. To mitigate these risks, suction-assisted technologies have emerged as vital adjuncts to traditional flexible ureteroscopy (FURS).The Flexible and Navigable Access Sheath (FANS) represents a significant evolution in this field. Unlike traditional rigid sheaths, FANS features a deflectable tip that can be guided into specific calyces, allowing for synchronized suction and active fragment evacuation. Conversely, Direct In-Scope Suction (DISS) utilizes a sheathless approach, where suction is integrated directly into the ureteroscope. While DISS avoids potential ureteral trauma associated with access sheaths, FANS is often associated with shorter operative times due to its superior irrigation-aspiration efficiency.For renal stones measuring less than 2 cm, both techniques aim to optimize the "perfusion-absorption" balance, effectively clearing stone dust and debris while preventing pyelovenous reflux. However, comparative data specifically for smaller stones remains limited. This study evaluates the clinical efficacy, safety profiles, and operative outcomes of FANS versus DISS in the treatment of renal calculi < 2 cm, aiming to determine which suction modality provides the most favorable balance of procedural efficiency and patient safety.