The goal of this clinical trial is to determine whether the surgical position during retrograde intrarenal surgery (RIRS) affects stone-free rates in adults with kidney stones. The main questions it aims to answer are: * Does the modified lithotomy position result in a higher stone-free rate compared to the standard lithotomy position? * Are there differences in complication rates between the two surgical positions? Researchers will compare patients undergoing RIRS in the standard lithotomy position to those in the modified lithotomy position (30-degree Trendelenburg with elevated surgical side) to assess its impact on stone clearance and surgical outcomes. Participants will: * Be randomly assigned to one of two surgical positions * Undergo RIRS with standard surgical procedures * Have follow-up imaging to assess stone clearance after surgery This study aims to improve surgical techniques and patient outcomes in kidney stone treatment.