This study evaluates the safety and efficacy of the novel tip-flexible semi-rigid ureterorenoscope for the treatment of renal calculi using a prospective, randomized multicentre trial design. Half of participants will receive retrograde intrarenal surgery using the tip-flexible semi-rigid ureterorenoscope, while the other half participants will receive retrograde intrarenal surgery using the classic flexible ureteroscope.

Retrograde intrarenal surgery using flexible ureteroscope has become the first-line treatment for renal calculi < 3.0 cm and is recommended by the European Association of Urology due to its minimally-invasive nature and satisfactory result.

However, some limitations still remain. Poor maneuverability, extra costs for the ureteral access sheath, and high device vulnerability still preclude flexible ureteroscopy from wider distribution.

Recently, the investigators present a novel ureterorenoscope, which is composed of a retractable rigid sheath and a semi-rigid ureteroscope with a flexible part on the tip. When the flexible tip of the inner shaft maintains within the sheath, working in the "rigid mode", the tip-flexible semi-rigid ureterorenoscope is capable of passing either the orifice or the physiological tortuosity of the ureter with ease. When the inner shaft is extended beyond the sheath, the endoscope is switched to the "flexible mode", capable of performing an intrarenal approach.

This endoscope integrates the classic semi-rigid and flexible ureteroscope both structurally and functionally, and has been approved for clinical application by the China Food and Drug Administration. In this study, transverse comparison is designed to evaluate the safety and efficacy of the tip-flexible semi-rigid ureterorenoscope for the treatment of renal calculi.

Inclusion Criteria:

• Subject has provided informed consent and indicated a willingness to comply with study treatments
• Subject has a diagnosis of renal stones according to computer tomography (CT) and intravenous pyelogram (IVP) results
• Subject is a surgical candidate for the ureteroscopic approach
• Subject is 18-80 yrs of age
• Subject has a single stone < 3 cm in size (IVP), or multiple stones < 3 cm in cumulative size (IVP)
• Subject has a serum creatinine level within the normal range for the study center

Exclusion Criteria:

• Subject needs bilateral procedures within one-stage ureteroscopy
• Subject has an active urinary tract infection (e.g., cystitis, prostatitis, urethritis, etc.)
• Subject has been diagnosed with a urethral stricture or bladder neck contracture
• Subject has been diagnosed with a urinary tract infection related to stone obstruction within two weeks
• Subject has severe hematuria that might blur the vision of the endoscopy
• Subject has a disorder of the coagulation cascade system that would put the subject at risk for intraoperative or postoperative bleeding
• Subject is unable to discontinue anticoagulant and antiplatelet therapy preoperatively (3-5 d)
• Subject has other diseases and could not tolerate the endoscopic surgery
• Subject has any kind of anatomic abnormality of the urinary system that might have an influence on the surgery
• Subject has ipsilateral pre-stenting or previous ureteroscopy within six months
• Subject has been diagnosed with hydronephrosis larger than 3 cm according to the B-scan ultrasonography examination