Presented by: Amanda McCormac BS
University of California-Irvine, Department of Urology

Introduction

Using the novel UCI force sensor as an indicator of force for ureteral access sheath (UAS) insertion, we determined that splitting of the urothelium could be avoided if the insertion force was limited to ≤ 6 Newtons (N). Herein, we define the inherent, safe expandability of the human ureter using sequential passage of urethral dilators at ≤ 6 N.

Materials

Ureteral sizing was performed on 75 patients undergoing ureteroscopy by passing a series of 35 cm long urethral dilators in 2 Fr increments until 6 N was reached. Next, ureteroscopy was performed and a post-ureteroscopic lesion scale (PULS) grade was recorded. An appropriate size UAS was inserted and the URS procedure was completed. Multivariate logistic regression analysis was conducted to evaluate the impact of age, gender, tamsulosin and stents on the ability to pass ≥ 16 Fr dilators. 

Results

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Among 75 patients, 37 cm long, urethral dilators were successfully passed into the ureter up to the 6 N threshold in 37.3% at ≤ 12 Fr, 24% at 14 Fr, 24% at 16 Fr, and 14.6% at ≥ 18 Fr (18-24 Fr). The mean maximum dilator diameter was 14 Fr. Logistic regression revealed that preprocedural ureteral stenting favored passage of ≥ 16 Fr dilators (OR 15.47, 95% CI 1.44 – 166.86; p = 0.024). Neither gender nor age were significant differentiators. The effect of tamsulosin alone was not statistically significant (OR 0.60, 95% CI 0.15 – 2.32; p = 0.454). In addition, the interaction effect was not found significant; as such, stent plus tamsulosin did not differ from stent alone (OR for interaction = 1.85, range 0.089 – 38.63; p = 0.690). 

Conclusion

The unstented human ureter can be sized, without risk, to an average circumference of 14 Fr; this increased to 16 Fr in the pre-stented ureter. Preoperative administration of tamsulosin was of no benefit.

Funding

None.

Co-Authors

Sohrab N. Ali, MD
Department of Urology, University of California, Irvine

Paul Piedras, BS
Department of Urology, University of California, Irvine

Minh-Chau Vu, BS
Department of Urology, University of California, Irvine

Andrew S. Afyouni, BS
Department of Urology, University of California, Irvine

Zachary E. Tano, MD
Department of Urology, University of California, Irvine

Kathryn Osann, PHD
Department of Medicine and Program in Public Health, University of California, Irvine

Pengbo Jiang, MD
Department of Urology, University of California, Irvine

Roshan M. Patel, MD
Department of Urology, University of California, Irvine

Michael Klopfer, PHD
Henry Samueli School of Engineering, University of California, Irvine

Jaime Landman, MD
Department of Urology, University of California, Irvine

Ralph V. Clayman, MD
Department of Urology, University of California, Irvine