This randomized controlled clinical trial evaluated whether furosemide-assisted forced diuresis during flexible ureteroscopy reduced the residual fragment rate and improved the stone-free rate after flexible ureteroscopy for management of medium sized renal stones measuring up to 30 millimeters. Adult patients undergoing flexible ureteroscopy for renal stones were randomized into two parallel groups: an experimental group that received intravenous furosemide during the procedure and a control group that received standard perioperative and postoperative care without furosemide. Stone-free status and residual fragments were assessed using non-contrast computed tomography performed four weeks after the procedure, and residual fragments were classified by fragment size. Secondary outcomes included operative time, length of hospital stay, postoperative complications, total urine output in the first 24 hours, and the need for additional treatments for significant residual stones.

Inclusion Criteria:

• Adult patients aged 18 years or older.
• Patients who underwent flexible ureteroscopy for renal stones measuring 30 millimeters or less.

Exclusion Criteria:

• Patients with active urinary tract infection.
• Patients with a history of previous open renal surgery or renal trauma.
• Patients with contraindications to anesthesia, such as severe cardiac disease, uncontrolled diabetes mellitus, or severe coagulation disorder.
• Patients with severe renal impairment, defined as an estimated glomerular filtration rate less than 30 milliliters per minute per 1.73 square meters.
• Patients with a single kidney.
• Patients with contraindications to furosemide administration.
• Patients with congenital renal anomalies.

De-identified individual participant data that underlay the reported results were planned to be shared with other researchers. The shared data were planned to include baseline characteristics, stone characteristics, intraoperative details, stone-free outcome on non-contrast computed tomography at four weeks, and postoperative outcomes including complications, pain scores, urine output in the first 24 hours, and need for auxiliary treatment. A data dictionary was planned to be provided.

The data were planned to become available after completion of the study and acceptance of the thesis or publication of the primary results, and were planned to remain available for five years.

Access was planned to be provided to qualified researchers upon reasonable request, after review of a brief proposal and analysis plan, and after execution of a data use agreement. Data were planned to be shared in a secure electronic format with de-identification applied.