The Effect of Different Body Positions and Channel Sheaths on Retrograde Intrarenal Stone Surgery(RIRS) Treatment of Lower Pole Renal Stones: a Randomized Controlled Trial

Urolithiasis was one of the most frequently noted diseases in urology clinic, with an incidence ranged from 5 to 15% around the world. Retrograde flexible ureteroscopy (RIRS) is currently the first-line treatment for renal stones < 2cm in size. Lower pole renal stones(LPS) are a difficult problem for urologists. The inborn sharp infundibular-pelvic angle (IPA) designated an inferior stone-free rate(SFR) of 65-82.5% in LPS when compared to middle and/or upper pole stone. The flexible negative pressure suction ureteral sheath(f-URS) can facilitate RIRS to flush out the fragments and dust in time, and provide a clear vision and reduce the renal pelvis pressure(RPP) during operation. Therefore, in cases of LPS, f-URS combined with RIRS may show advantages. However, there is currently a lack of relevant prospective randomized controlled studies. Standard lithotomy position is the most commonly used position for RIRS. Besides the standard lithotomy position, other positions, such as the T-tilt position, are also available for RIRS in special cases. Investigators were inspired by this and proposed the lateral position, which is available for RIRS in cases of LPS.Theoretically, in standard lithotomy position, the renal pelvis and renal calyces were mostly distributed in a '-<' shaped structure on the horizontal plane. However, the renal pelvis and renal calyxes would be stood up in a 'Y'-shaped structure when patients laid in lateral position. And gravity will make the calyceal stones at the dome fall into the renal pelvis naturally during the lithotripsy. In long-term clinical practice, researchers have found that the change of position and the use of f-UAS can improve SFR. The investigators aimed to conduct a prospective randomized controlled trial to compare the SFR of different positions and different ureteral sheaths.