Examining the Impact of Different Properties of Ureteral Access Sheaths in Reducing Insertion Force During Retrograde Intrarenal Surgery: An Study.

This study aimed to evaluate the characteristics of ureteral access sheaths (UASs) that can reduce the insertion force while accessing the upper urinary tract. Six different types of 12/14F UASs were used. We evaluated the properties of UASs such as the diameter of the outer sheath, length of the inner dilator tip exposed from the outer sheath, sheath flexibility (assessed in terms of bending force of the tip or base), flexibility ratio (i.e., bending force value of tip-to-base ratio), and frictional force of the outer sheath surface. We measured the force required for inserting the UAS into an artificial ureteral model and examined the correlation between the relevant characteristics and insertion force for each UAS. Overall, a lower tip-to-base flexibility ratio ( = 0.66) and a lower frictional force ( = 0.50) were inversely correlated with insertion force. The force of insertion into the bifurcation was associated with the flexibility of the base ( = -0.64), flexibility ratio ( = 0.79), and frictional force ( = 0.66). Moreover, a shorter dilator tip ( = 0.52), lower flexibility ratio ( = 0.52), and lower frictional force ( = 0.50) were correlated with a lower insertion force at the proximal ureter. A UAS with a rigid base and flexible tip parts, a smoother surface, and a shorter dilator tip would be preferable for reducing the insertion force. These findings may be crucial for selecting or developing an ideal UAS that can decrease the risk of ureteral injury.