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.

Inclusion Criteria:

• Presence of single or multiple kidney stones, with the largest stone ≤2 cm
• Age ≥18 years
• Provided written informed consent to participate in the study
• Indicated for retrograde intrarenal surgery (RIRS) as a treatment approach

Exclusion Criteria:

• Severe cardiovascular disease (e.g., heart failure)
• Congenital kidney anomalies (e.g., horseshoe kidney, ectopic kidney)
• Concurrent ureteral stones
• Pregnancy or planning pregnancy
• History of previous kidney surgery on the same side
• Active urinary tract infection (UTI)
• Coagulopathy or use of anticoagulant therapy that cannot be stopped before surgery