Determining the Safety Threshold for the Passage of a Ureteral Access Sheath in Clinical Practice Using a Purpose-Built Force Sensor.

PURPOSE Ureteral injury is a frequent complication of ureteral access sheath (UAS) deployment. We sought to define the safe threshold of force for the passage of a UAS using a novel UAS Force Sensor (UAS-FS). MATERIALS AND METHODS UAS-FS measurements were recorded in 210 renal units. A 16Fr UAS was deployed initially; based on a prior porcine study. If 6N was reached, the surgeon was advised to downsize the 16Fr UAS. . In each case, a post-ureteroscopic lesion scale (PULS) was recorded. Regression models were used to estimate the impact of adjusted variables on PULS grade, 16Fr UAS deployment, and peak force. RESULTS A 16Fr UAS was deployed in 127 (61%) renal units with a mean peak force of 5.7N. Two high-grade ureteral injuries occurred; in both cases >6N of force was recorded. PULS grade correlated directly with peak insertion force (p <0.01). Bacteriuria within 60 days of the procedure (OR 2.009, p=0.034), combination of preoperative stent plus oral tamsulosin (OR 2.998, p=0.045), and prior ipsilateral stone surgery (OR 2.13, p=0.01) were independent predictors of successful 16Fr UAS deployment. Among patients with neither prior ipsilateral stone surgery nor preoperative stent, preoperative tamsulosin facilitated passage of a 16Fr UAS (OR 2.750, p=0.034). CONCLUSIONS UAS associated ureteral injury can be averted by limiting the insertion force to ≤6N. Prior stone surgery, preoperative indwelling ureteral stent plus oral tamsulosin, and recently treated bacteriuria favored passage of a 16Fr UAS. In the naive, unstented patient, preoperative tamsulosin favored deployment of a 16Fr UAS.