Kidney stones are a common health problem and may recur frequently, which can affect quality of life and kidney function. Retrograde intrarenal surgery (RIRS) is a minimally invasive treatment used for renal stones, but treatment of medium-sized stones may be associated with longer operative time, impaired visibility during surgery, residual stone fragments, and postoperative infectious complications caused by increased intrarenal pressure.

Suction-assisted retrograde intrarenal surgery (RIRS) techniques have been developed to improve surgical efficiency and safety by facilitating continuous removal of stone fragments and helping control intrarenal pressure. Two commonly used suction-assisted approaches are direct in-scope suction (DISS) and flexible and navigable suction ureteric access sheath (FANS). However, there is limited prospective randomized evidence directly comparing these two techniques.

This randomized prospective clinical study aims to compare direct in-scope suction (DISS) versus flexible and navigable suction ureteric access sheath (FANS) in adult patients with medium-sized renal stones measuring 2 to 3 cm who are undergoing retrograde intrarenal surgery (RIRS). Participants will be randomly assigned to one of the two suction-assisted techniques. The study will evaluate whether flexible and navigable suction ureteric access sheath (FANS) provides better outcomes than direct in-scope suction (DISS) in terms of stone-free rate and postoperative infection rate.

The primary outcome is stone-free status assessed by postoperative imaging. Secondary outcomes include operative time, intraoperative visibility, and postoperative complications, particularly infection and urosepsis. The study hypothesis is that suction-assisted retrograde intrarenal surgery (RIRS) using the flexible and navigable suction ureteric access sheath (FANS) technique will result in a higher stone-free rate and a lower postoperative infection rate compared with direct in-scope suction (DISS) in the management of medium-sized renal stones.

Inclusion Criteria:

• Adults aged 18 to 60 years
• Radiologically confirmed renal stones measuring 2 to 3 centimeters
• Eligible for retrograde intrarenal surgery
• Normal renal function as evidenced by normal serum creatinine
• Able and willing to provide written informed consent

Exclusion Criteria:

• Pregnancy or lactation
• Active urinary tract infection at the time of enrollment
• Bleeding disorders or coagulopathies that contraindicate surgical intervention
• Anatomical malformations affecting the urinary tract
• Solitary kidney
• Inability or unwillingness to provide informed consent

De-identified individual participant data underlying the results reported in this study will be made available, including demographic data, baseline characteristics, intervention allocation, outcome measures, and adverse event data.

Data will become available beginning 6 months after publication of the main study results and will remain available for 5 years.

Data will be available to qualified researchers who provide a methodologically sound research proposal. Requests should be directed to the corresponding investigator. Access will be granted after review and approval of the proposal and execution of a data access agreement, with use limited to the purposes described in the approved proposal.

This is an open-label surgical trial. The operating urologist cannot be masked because the two suction-assisted retrograde intrarenal surgery techniques require different instruments and procedural steps. Participants will undergo one assigned procedure according to the study protocol. Outcome assessment will be based on predefined clinical, laboratory, and imaging measures.