Abstracts from the New England Section of the AUA 2021

NE-AUA 2021 Abstracts Scientific Session II: Stones I Computer Modeling for Optimization of Endourological Robotic Devices Daniel C. Leslie, PhD , Liz B. Wang, MD, Max McCandless, BS, Harin Lee, BS, Sheila Russo, PhD, David S. Wang, MD, Shaun E. Wason, MD Boston University School of Medicine, Boston, MA, USA Introduction: Soft robotics uses deformable materials to create minimally invasive surgical devices and has implications in endourology, where gentle manipulation of tissue is crucial. We propose a novel soft robotic anti- retropulsion device to prevent stone migration during ureteroscopy. The ideal anti-retropulsion device must be thin enough to slide past a ureteral stone, yet be able to deploy and expand to over 10mm in diameter to prevent proximal stone fragment migration. To reduce in-person laboratory work during the COVID-19 pandemic, we use commercially available software to design and test our device. Materials & Methods: Prototype soft robotic anti-retropulsion devices and actuators were tested in the finite element modeling (FEM) software, Abaqus (Dassault Systèmes). Material properties were programmed frompreviously published, experimentally validated soft robotic actuator modeling. We used Ecoflex 00-30 silicone given its superior compliance (expansion under pressure) for balloon actuation. Simulated pressure was applied to the inner surface of balloon actuators of varying dimensions, and the final geometry (deformation) after expansion under pressure was modeled. Results: Configurations of soft robotic actuators were iteratively designed and tested in Abaqus software. The initial device design was a cylindrical, 1-mm-diameter balloon tested at 0.1mm and 0.05mm thickness of Ecoflex silicone. Simulated pressure of 30kPa (4.5 PSI) and 20kPA (3 PSI) resulted in deformation diameters of 4.5mm and 7.3mm, respectively, below our ideal 10mm diameter. Final device design (below) was 1mm thick and planar, resulting in deformations greater than 12mm at 10kPa (1.5 PSI), large enough to prevent stonemigration proximally in a dilated ureter. Our device conforms to the irregular geometry of the ureter upon deployment with low pressure actuation. This minimizes the potential tissue trauma when compared with current high pressure, low compliance balloons (861 kPa, 125 PSI) or metal devices. Conclusions: Computer modeling tools enable rapid prototyping of soft robotic endourological surgical devices. We demonstrate by optimizing balloon deformation under pressure for a novel soft robotic anti-retropulsion device. Our final design can slide by ureteral stones then gently actuate over 12mm at low pressure to minimize tissue trauma. Association of Urinary Stone Surgery and Patient-reported Complications in Spinal Cord Injury Khushabu Kasabwala, MD 1 , Michael Borofsky, MD 2 , John Stoffel, MD 3 , Blayne Welk, MD, MSc 4 , Jeremy B. Myers, MD 5 , Sara M. Lenherr, MD 5 , Sean P. Elliott, MD 2 1 Lahey Hospital and Medical Center, Burlington, MA, USA; 2 University of Minnesota, Minneapolis, MN, USA; 3 University of Michigan, Ann Arbor, MI, USA; 4 Western University, London, ON, Canada; 5 University of Utah, Salt Lake City, UT, USA Introduction: People with spinal cord injury (SCI) have an increased risk of urinary stone formation and an increased risk of morbidity from the surgeries to remove them. Some have postulated that the highest risk of stones is in the first year after SCI yet the natural history and health-related impact of stone disease among this patient population remains poorly defined. We hypothesized that a history of urinary stones requiring surgery would be associated with an increased incidence of SCI-related complications and lower quality of life (QOL). Materials &Methods: 1479 participants with SCI in the Neurogenic Bladder Research Group registry were asked about urinary stone history (pre-dating or since SCI), SCI-related complications and neurogenic bladder-relatedQOL. Eligibility: age ≥ 18 years with acquired SCI and followed for 12 months. Neurogenic Bladder Symptom Score (NBSS) score was used to determine bladder symptoms for QOL assessment. Continuous variables and NBSS categories were compared by the t-test and categorical variables were compared by the chi-square test (R version 3.5.2). Because the presence of stones was assessed by participant recall, we stratified our groups by history of stone surgery in order to ensure we were capturing clinically significant urinary calcifications. Results: At study entry participants were a median of 11 years post-SCI and 189 (12.8%) reported a history of bladder or kidney stones surgery; 99.5% of these occurred after the SCI. Median time between SCI and the first stone was 5.6 years (interquartile range [IQR] 1.8-12.8). During the year of observation, the incidence of stone surgery was 8% - 9% in those with a remote history of stone surgery and 2%per year in those without prior stone surgery (p=0.001). SCI-related complications and QOL are shown in Table 1 . There was no significant difference in the rate of patient-reported UTIs but there was an increased incidence of UTI-related hospitalizations in those with prior kidney (18%) or bladder stone surgery (16%) compared to those with no stone surgery (11%, p=0.013). There was a higher rate of hospitalization for those with a history of stone surgery, with common reasons including blood clots, UTI, pressure ulcers and pneumonia (p=0.001). There was no clinically significant difference in NBSS QOL domains across the three cohorts. Conclusions: People with SCI are at high risk for urinary stones and this risk continues over the long term. People who experience a stone are at increased risk for future stones. Kidney stones are associated with other negative outcomes such as hospitalization for UTI, pressure ulcers, deep venous thrombosis and pneumonia though they do not appear to affect QOL. People with a history of urinary stones warrant careful surveillance both for additional stone episodes and for other negative health outcomes. 16 15 9