Ureteral Access Sheath Deployment: Understanding the Force Tolerance of the Human Ureter and the Development of Ureteral Injury During Endoscopic Surgery

Background/Objective: Ureteral injury is a clinical concern during placement of a ureteral access sheath (UAS). Herein, we identify factors contributing to the clinically successful passage of 16F UASs using a previously established safe force threshold of ≤6 Newtons (N). Methods: UAS force sensor measurements were recorded during ureteroscopic procedures in 250 renal units (238 patients). If 6 N was reached during insertion of the UAS, the surgeon was advised to downsize from a 16F UAS to a smaller sheath. In each case, a post-ureteroscopic lesion scale (PULS) grade was recorded. Results: A 16F UAS was safely deployed in 145 (58%) renal units with a mean maximum force of 5.5 N. Two renal units sustained a high-grade ureteral injury (PULS 3), both of which had forces of deployment ≥8 N. Independent favorable factors for passage of a 16F UAS included: presence of a preoperative indwelling ureteral stent (76.5% passage) (OR: 3.049, p = 0.002) and a course of oral antibiotics within 6 weeks of the procedure with or without an associated urinary tract infection (68.4% and 59.6% passage) (OR: 3.133, p = 0.002 and 2.046, p = 0.034). Preoperative tamsulosin was not of benefit. Conclusions: Adherence to a force threshold of ≤6 N during UAS passage resulted in safe passage of a 16F UAS in 58% of 250 renal units; when adhering to the recommended ≤6 N force threshold, there were no PULS 3 injuries. A preexisting indwelling ureteral stent and administration of antibiotics within 6 weeks of the procedure independently favored safe passage of a 16F UAS.