Dusting vs Fragmentation Laser Cystolithotripsy for Pediatric Bladder Stones (DUST-FRAG-PED)

This is a prospective randomized controlled trial conducted at the Department of Urology, Faculty of Medicine, Beni-Suef University Hospital.

The study will include children with radiologically confirmed single bladder stones less than 3 cm who are planned for transurethral Holmium:YAG laser cystolithotripsy and are suitable for transurethral endoscopic management under general anesthesia. Written informed consent will be obtained from parents or legal guardians before enrollment.

Eligible children will be randomized in a 1:1 ratio into two groups. Participants in the dusting group will undergo transurethral Holmium:YAG laser cystolithotripsy using low pulse energy and higher pulse frequency settings, with the aim of reducing the stone into fine particulate debris and tiny fragments with minimal need for active extraction. Participants in the fragmentation group will undergo transurethral Holmium:YAG laser cystolithotripsy using higher pulse energy and lower pulse frequency settings, with the aim of producing visible extractable fragments that can be actively removed when needed.

All procedures will be performed under general anesthesia in the lithotomy position using a pediatric semi-rigid ureteroscope. A Holmium:YAG laser will be used in both groups. The planned settings are 0.5-0.8 J and 10-15 Hz in the dusting group, and 1.0 J and 6-10 Hz in the fragmentation group. A 550-micron end-firing laser fiber will be preferred when compatible with the available endoscope.

The primary outcome is total operative time, defined as the time in minutes from insertion of the endoscope into the urethra until completion of stone clearance and termination of the procedure, including fragment retrieval when required. Secondary outcomes include laser time, need for active fragment extraction, endoscopic stone-free status at the end of the procedure, ultrasound-assessed stone-free status at follow-up, intraoperative mucosal injury or bleeding, need for postoperative catheterization, postoperative hematuria, dysuria, urinary tract infection, and hospital stay. Follow-up will be scheduled at 1 week, 1 month, and 3 months with clinical assessment and ultrasonography.