The aim of this study is to evaluate and assess the outcomes of flexible ureteroscopy (FURS) with flexible and navigable suction UAS (FANS) in the treatment of lower calyceal stones.

With the continued advancements of technology and increasing experience gained by urologists in ureteroscopic skills, fURS has become a standard treatment for kidney stones lesser than 2 cm in diameter. In the previous the European guidelines and American Urologic Association guidelines for management of urolithiasis, fURS were recommended as a second-line treatment for stones less than 2 cm after ESWL, however in the recent revision of the guidelines, RIRS can be used as the first-line management option especially for stones measuring between 11 and 20 mm.

The ureteral access sheath (UAS), initially introduced by Hisao Takayasu in 1974 Despite continued advances in retrograde intrarenal surgery (RIRS), recent real-world data for 6669 patients in the FLEXOR registry revealed residual fragments in 21.7% of patients, of whom 51.5% required a second intervention.

The sepsis rate in the same study was just 1.3%. Hence, there is still much to improve in terms of technical expertise and technology for RIRS. Many aids have been introduced to streamline RIRS and improve procedural success. These include suction via a scope or ureteral access sheath (UAS), postintervention catheters, slimmer single-use scopes, and high-power lasers, these improvements have made RIRS a standard of care according to international guidelines.

It has been reported that vacuum aided or suction aspiration sheaths have strong potential to improve the stone-free status (SFS) rate and minimize infectious compilations associated with the negative effects of high intrarenal pressure and temperature, However, the true potential of the advances for RIRS has yet to be investigated. The ideal game-changing technological innovation for RIRS should improve all key outcomes of the procedure, including the rate of immediate single stage SFS, perioperative and postoperative complications, and the reintervention rate for residual fragments. One recent advance that has shown much promise is a flexible and navigable sheath (FANS) So, we will conduct a prospective study to assess whether FANS could be a potential game-changer for RIRS in adults with lower calyceal stones instead of traditional UAS especially regarding stone-free rates (SFR), complications and cost.

Inclusion Criteria:

1. Adult patients ≥ 18 years old.
2. Patients with lower calyceal stones scheduled for FURS.

Exclusion Criteria:

1. patients with active urinary tract infections.
2. Patients with renal and ureteric anomalies.
3. patients with coagulopathy
4. patients who are refusing to participate.

De-identified individual participant data will be available upon reasonable request from qualified researchers after study completion. A data dictionary will also be provided.

Time Frame: 6 months after final publication, available for 3 years. Access Criteria: Contact the principal investigator.