Abstracts from the New England Section of the AUA 2020: A Virtual Experience

© The Canadian Journal of Urology TM : International Supplement, August 2020 Scientific Session II: Stones I Development of a Novel Metric to Preoperatively Estimate Flexible Ureteroscopy Operative Time: “The Stone Treatment Scale (STS)” DavidW. Sobel, MD , Timothy O’Rourke, MD, Rebecca Ortiz, BA, Nicole Thomasian, BS, Philip Caffery, PhD, Christopher Tucci, MS, Gyan Pareek, MD Brown University, Providence, RI Introduction: As operating room (OR) time is a fixed commodity, new methods are needed to improve the accuracy of room time estimates to mitigate underutilization. We sought to develop a surgeon-friendly metric for flexible ureteroscopy and laser lithotripsy (URSLL) similar to prostate ablation rates by which urologists can better estimate case time for improved perioperative planning. Materials &Methods: Aretrospective review of all flexible URSLLprocedures of calcium oxalate (CaOx) stones performed from December 2016 to April 2018 performed by 11 urologists at an academic institution was conducted. Patient characteristics, imaging, operative times, and outcomes were analyzed. Cases were included if preoperative computed tomography (CT) imaging was available and the patient was rendered stone free either by postoperative imaging or intraoperative surgeon interpretation. All cases were performed with a Lumenis Pulse 30H laser unit and dusting technique. Procedure length was measured by case start-to-case completion times. A novel measure of stone treatment efficiency was calculated for each case as stone burden treated (millimeter/ operative time [minutes]). Differences between urologists were assessed through one-way analysis of variance (ANOVA). Results: 69 CaOx flexible URSLL procedures were reviewed. 37 (54%) of patients were female; 60 (86%) of patients had postoperative imaging demonstrating stone-free status and 35 (51%) patients were declared visually stone free at completion of the case. The mean stone size was 9.2 mm ( R 3-24, SD 4.53) and the mean operative time was 42 minutes ( R 9-158, SD 27.7). The mean STES amongst all urologists studied was 0.3 mm/minute ( R 0.38-1.33 SD 0.19) (Table 1). A significant difference between urologists was identified utilizing this novel metric of efficiency [ F (10,58) = 3.758, p =.006] (Figure 1). The most efficient mean urologist STS in this series was 0.60 mm/minute and the least was 0.16. Conclusions: The Stone Treatment Score (STS) can be a valuable metric for determining a urologist’s efficiency to completely clear stone ureteroscopically within a set of technological constraints (laser power, technique). Operative scheduling may allow for more cases per operative day based on the efficiency a surgeon can achieve. This metric may be used to compare surgeon performance as well as create opportunities to improve perioperative planning and operating room utilization. The most efficient urologist by this metric in our study was a fellowship-trained endourologist. Further investigation as to factors associated with efficiency in the STS including assistant (resident or fellow) training year and experience. Further study to validate this metric against other operative efficiency estimates is warranted. Renal Pelvis Pressures During Ureteroscopy Predict Pyelovenous Absorption in a Porcine Model Jeffrey K. Twum-Ampofo, MD 1 , Jennifer Saunders, MS 2 , Marle Franco, BS 3 , Brian H. Eisner, MD 1 1 Massachusetts General Hospital, Boston, MA; 2 Boston Scientific, Boston, MA; 3 Boston Scientific, Marlborough, MA Introduction: Renal pelvis pressures and pyelovenous backflow during ureteroscopy are hypothesized to play a role in the development of infection after ureterorenoscopy. However, there are few studies in the literature which investigate this phenomon and the relationship between renal pelvis pressure, operative time, and pyelovenous backflow is poorly understood. Herein we present a pilot study of ureteroscopy in a swine model designed to evaluate these relationships. Materials & Methods: In anesthetized pigs (n = 9; female; ~60 kg each), ureteroscopy was performed as follows: cystoscopy was performed to position a 0.018” pressure sensor guidewire (Comet™, Boston Scientific, Marlborough, MA) and standard guidewire. A flexible ureteroscope was then introduced into the renal pelvis and the position of the ureteroscope and the pressure sensor wire were confirmed. Infusion of irrigation fluid (5% ethanol in saline) at target renal pelvic pressures (37-150 mmHg) was maintained for 60 minutes using a pressure bag and instantaneous feedback from the pressure-sensing guidewire.Venousbloodsamplingwasperformedevery10minutes.Each trialstartedwith blood EtOH of 0 mg/dL. Volume of irrigant absorbed was determined with established equations utilizing animal blood EtOH, weight, and irrigation concentration. Results: Fourteen (14) pig kidneys were used during the study. The average irrigation volume absorbed after 60 minutes of irrigation were 4.9, 7.9, 24.9, and 72.5 mL of fluid at renal pelvis pressures of 37, 55, 75, and 150 mmHg, respectively ( P = 0.07).At renal pelvis pressures of 55 mmHg and above, pyelovenous backflow occurred as early as 20 minutes. At renal pelvis pressures of 37 mm Hg, pyelovenous backflow was not measured until at least 40 minutes of procedure time. Increasing renal pelvis pressures were associated with increases in fluid absorption for all pressures tested [Figure 1]. Conclusions: In this study of a swine model of ureteroscopy, increasing renal pelvis pressures during ureteroscopy were associated with increases in fluid absorption as well as more rapid fluid absorption. This model may be used in the future to better understand the relationshipbetweenrenalpelvispressureandpyelovenousbackflowduringureteroscopy. 13 12 6