Two Types of Single-use Flexible Ureteroscopies for the Treatment of Upper Urinary Tract Stones in Children

Inclusion Criteria: * Patients scheduled for ureteroscopy and laser lithotripsy for individual renal stones ranging in size from 5 mm to 20 mm in all intrarenal locations (If there are multiple stones present, the total stone burden in cross section should not exceed 20 mm) * Patients \< 14 years * For children younger than 8 years old, the informed consent form is signed by the parents; for children older than 8 years old, the informed consent form is signed by both the parents and the child themselves. Exclusion Criteria: * Children with uncontrolled urinary tract infections or coagulation disorders and other contraindications for surgery before the operation. * Children with severe renal insufficiency, anatomical or functional solitary kidney, known nephrocalcinosis, and other significant comorbidities that are not suitable for participating in the study. * Children who refuse to participate in this study. * Any other reason that in the opinion of the investigator would make the participant unsuitable for enrollment in the study.