MP04-04 DEVELOPMENT AND VALIDATION OF AN IN VITRO KIDNEY MODEL FOR MEASURING INTRAPELVIC PRESSURE DURING URETEROSCOPY

INTRODUCTION AND OBJECTIVE: During ureteroscopy (URS), rises in intrapelvic pressure (IPP) may increase the risk of infectious complications. While IPP is well studied in in vivo models, it has only been studied in one modest in vitro model. Anatomically accurate in vitro models that can mimic IPP profiles of in vivo kidneys are lacking. The aims of this study were to (1) modify an in vitro kidney model for use in simulated ureteroscopic studies, (2) validate its IPP profile against in vivo data. METHODS: The distal end of the ureter of a synthetic kidney model that permits intrarenal navigation (Simagine Health, WA) was partially occluded with silicone to ensure a fluid-tight seal around inserted instruments. A screw-type Tuohy-Borst valve (Merit Medical, UT) was attached to a custom silicone tube that was inserted into a hole in the renal pelvis. A pressure sensor (Opsens, Canada) was fed through the valve into the pelvis. To calibrate the model, a Cobra ureteroscope (Richard Wolf, Germany) was inserted to the mid-pelvis. Under 200 cmH2O irrigation, the seal between the pressure sensor and the valve was adjusted until the kidney achieved a plateau IPP of 54 cmH2O, which is the reported human IPP at that irrigation pressure. Experiments were conducted with the Cobra scope placed in the mid-pelvis, with and without ureteral access sheaths (11/13, 13/15; Navigator, Boston Scientific, MA) at irrigation pressures of 61, 102, 153, and 193 cmH2O using an automated irrigation system (Endoflow, RocaMed, MN). Study outcome was steady state IPPs for each condition. RESULTS: Fluid flowed out of the valve at the renal pelvis in a controlled manner, which was critical to simulate ureteric outflow during URS. Figure 1 depicts the steady state IPP for each condition. With the use of a sheath, IPP remained below the pyelovenous backflow limit (40 cmH2O) at all irrigation pressures, while without a sheath, IPP surpassed this limit at higher irrigation pressures. Most importantly, the IPP for these conditions corresponded well with published data from in vivo studies. CONCLUSIONS: Our in vitro kidney model can simulate in vivo IPP profiles and can be tailored to different conditions by controlling fluid outflow. This model allows for bench testing of technologies aimed at mitigating rises in IPP during URS.Source of Funding: University of Michigan Kickstart Funding

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