News

How to Select the Right Ureteral Access Sheath for URS

ENDOUROLOGY How to Select the Right Ureteral Access Sheath for URS CincyMed Clinical Resource  ·  4 min read The ureteral access sheath (UAS) has become a cornerstone instrument in flexible ureteroscopy (fURS), providing stable ureter access, facilitating multiple scope passes, and improving irrigation flow during stone management procedures. Selecting the appropriate sheath size and working length directly affects operative efficiency, stone-free rates, and patient safety. This guide provides the clinical framework endourologists and stone surgeons need to make confident instrument selections. What Is a Ureteral Access Sheath? A ureteral access sheath is a dual-lumen introducer — an inner dilating obturator and an outer working sheath — inserted over a guidewire into the ureter under fluoroscopic guidance. Once seated, the inner dilator is removed, leaving a low-resistance conduit through which a flexible ureteroscope can be repeatedly passed without traumatizing the ureteral mucosa. The sheath also augments intrarenal pressure management by allowing passive outflow around the scope shaft. UAS Size Selection: French Sizing Guide Ureteral access sheaths are sized by the inner diameter (ID) of the outer sheath and the outer diameter (OD) of the combined assembly. Choosing the right size balances scope passage ease against ureteral trauma risk. Sheath Size (ID/OD) Compatible Scope OD Working Length Primary Use Case 9.5/11.5 Fr Up to 8.7 Fr scope 35 cm Proximal ureter stones, pediatric or small ureter 11/13 Fr Up to 9.9 Fr scope 35–45 cm Standard adult fURS, single renal access 12/14 Fr Up to 11 Fr scope 45–55 cm Larger renal stones, multiple scope passes required 14/16 Fr Wide-bore scope or dual-lumen work 55 cm Complex staghorn, PCNL-adjunct ureteroscopy Working Length Considerations The working length of the UAS must span from the urethral meatus to a position just below the ureteropelvic junction (UPJ). Standard adult lengths range from 35 cm (suitable for distal and mid-ureter access) to 55 cm (for tall patients or long upper-tract access). Measure patient height and confirm UPJ position fluoroscopically before committing to sheath length. An undersized working length risks sheath migration into the ureter; an oversized length may impinge on the UPJ and increase the risk of urothelial injury. Most endourologists keep both 35 cm and 45 cm sheaths available in the OR. Pre-Dilation and Ureteral Stenting Placement of a ureteral stent 24–48 hours before URS ("pre-stenting") is strongly supported by clinical evidence for passive ureteral dilation, improving UAS passage and reducing ureteral avulsion risk — particularly when using sheaths larger than 11/13 Fr. The PubMed literature consistently demonstrates improved stone-free rates and reduced operative time when pre-stenting is employed before complex renal stone cases. If passive dilation has not been performed, balloon ureteral dilators can achieve active dilation intraoperatively. Confirm ureteral access before UAS insertion using a safety guidewire to protect against complete access loss. Hydrophilic vs. PTFE Coatings Most contemporary ureteral access sheaths feature a hydrophilic or polytetrafluoroethylene (PTFE)-coated outer surface to reduce insertion friction and urothelial trauma. Hydrophilic coatings become lubricious on contact with saline and are preferred for tortuous or narrow ureters. PTFE-coated sheaths are durable and maintain low friction across longer insertion distances. Confirm sheath coating compatibility with your irrigation fluid of choice before use. Intrarenal Pressure Management Elevated intrarenal pressure during fURS is associated with sepsis risk, particularly in patients with infected urine or obstructed systems. A properly seated UAS allows passive pressure venting around the scope shaft, keeping renal pelvis pressures below the threshold for pyelovenous backflow. Select a sheath with adequate ID-to-scope clearance — at least 1 Fr of annular space — to ensure passive drainage during active irrigation. Browse our complete selection of ureteral access sheaths and flexible ureteroscopes to configure your URS instrument set. Key Selection Checklist Confirm ureteroscope OD against sheath ID before the case Select working length based on patient height and UPJ position Use pre-stenting for sheaths ≥12/14 Fr or narrow native ureters Choose hydrophilic coating for tortuous ureters Maintain ≥1 Fr annular clearance for passive intrarenal pressure relief Always advance the sheath over a safety wire under fluoroscopic guidance Conclusion Proper ureteral access sheath selection is as important as scope selection in determining URS outcomes. Matching sheath size to scope OD, selecting appropriate working length, and ensuring adequate ureteral preparation are the three pillars of safe and efficient ureteroscopy. A well-chosen UAS protects the ureter, preserves scope optics, and enables the multiple scope passes often required for complete stone clearance. Need instruments for this procedure? CincyMed supplies surgical and endoscopy instruments for hospitals and ASCs. Browse Our Catalog