Presented by: Seyed Amiryaghoub M. Lavasani
University of California, Irvine

Introduction

Although ureteral access sheaths (UAS) can facilitate ureteroscopy (URS), they can also cause ureteral injury. Our earlier studies showed that limiting the force applied during UAS passage to 6 Newtons (N) can prevent injuries, while high-grade injuries (splitting of the urothelium) occurred at forces above 8 N. Others have published that high grade ureteral injury occurred after the passage of a 14 Fr UAS in 13-26% of patients. Accordingly, we developed a model to determine how much force urologists and residents-in-training typically might use during UAS insertion.

Materials

Urologists with varying levels of experience were recruited from the 2022 American Urological Association and World Congress of Endourology meetings. Participants passed three UAS(s) (12, 14, and 16 Fr) into a male genitourinary model that contained a concealed force sensor. The participants were blinded to the fact that the exerted force was being recorded. An online survey was utilized to collect demographic data. Predictive factors of 16 Fr UAS placement forces outside of two predetermined ranges (4 N – 6 N or 4 N – 8 N) were ascertained through a polychotomous logistic regression (PLR). 

Results

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Among 121 participants inserting a 16 Fr UAS, 55 (45%) and 39 (32%) applied UAS forces exceeding 6 N and 8 N respectively, while 35 (29%) remained below 4 N. More years of practice was significantly associated with generating forces above 6N (Table 1A and 1B) (force > 6 N OR 1.049, 95% CI 1.004 - 1.096, p = 0.032) and force > 8 N (OR 1.04, 95% CI 1.001 - 1.081, p = 0.045). Performing less than 20 URS cases per month had a significantly lower likelihood of applying forces less than the 4 N – 8 N reference range (1 - 10 URS: OR 0.231, 95% CI 0.069 - 0.771, p = 0.017; 11 - 20 URS: OR 0.3, 95% CI 0.095 - 0.95, p = 0.041).

Conclusion

In conclusion, 32% of urologists exceeded the 8 N safety threshold; this group was positively associated with more years of practice.  Conversely, 29% of urologists fell short of 4 N and thus exerted too little force when placing the UAS which might lead to using an undersized UAS; this group typically performed < 20 URS/month. These findings highlight the potential benefit of monitoring UAS insertion force in order to both avoid placing an undersized UAS (i.e., less procedural efficiency) or at the other extreme, avoiding ureteral injury. 

Funding

None.

Co-Authors

Kalon L. Morgan,
University of California, Irvine

Allen Rojhani,
University of California, Irvine

Andrei D. Cumpanas,
University of California, Irvine

Rohit Bhatt,
University of California, Irvine

Mariah Hernandez,
University of California, Irvine

Kelvin Vo,
University of California, Irvine

Amanda McCormac,
University of California, Irvine

Paul Piedras,
University of California, Irvine

Nina Kar,
University of California, Irvine

Minh-Chau Vu,
University of California, Irvine

Seyedamirvala Sadaat,
University of California, Irvine

Ahmad Abdel-Aziz, MD
University of California, Irvine

Antonio R. H. Gorgen, MD
University of California, Irvine

Seyed Hossein H. Sharifi, MD
University of California, Irvine

Zachary E. Tano, MD
University of California, Irvine

Sohrab N. Ali, MD
University of California, Irvine

Pengbo Jiang, MD
University of California, Irvine

Roshan M. Patel, MD
University of California, Irvine

Jaime Landman, MD
University of California, Irvine

Ralph V. Clayman, MD
University of California, Irvine