Comparison of the safety and efficiency of flexible ureteroscopy with the different hanged water heights in a kidney model

Abstract Objective To develop an in vitro model of the renal pelvis to compare intrarenal pressure(IRP) and irrigation flow at various suspended water heights during flexible ureteroscopy (fURS). Methods A 100 mL saline bag was used to simulate the renal pelvis. The fURS sheath was connected to the bag and the ureteric access sheath (UAS) was positioned at the junction of the ureteropelvic region. Central venous pressure tubing was connected to monitor the pressure in the renal pelvis under different conditions. Two different sheath sizes (12Fr and 14Fr) were tested with fURS sizes of 7.5, 8.5, and 9.5Fr, respectively. The perfusion method was gravity based, and the hanging water heights were set at 60, 90, 120, 150, and 180 cm. A separate manual pumping group was also measured. Results In the group using a 12Fr sheath, the use of a 9.5Fr flexible ureteroscope without accessories resulted in a minimum gravity perfusion pressure of 8.4 cmH2O and a maximum pressure of 17.5cmH2O. However, manually administering perfusion in the pelvis produced pressures exceeding 60cmH2O. When the fURS was employed with a 200um laser fiber within the same sheath size, the minimum pressure of gravity perfusion decreased to 6.4cmH2O, and the maximum pressure was 10.5cmH2O. The IRP reached 48cmH2O while hand pumping. In the 14Fr sheath group, while using a 9.5Fr fURS, minimum and maximum gravity perfusion pressures were 2.5cmH2O and 6.0cmH2O, respectively. In contrast, manual perfusion resulted in a pressure of 17cmH2O. For the 12Fr sheath group using a 7.5Fr fURS, the minimum pressure of gravity perfusion was 5.4cmH2O, the maximum was 8.2H2O, and renal pelvic pressure during manual perfusion was 25.5cmH2O. Conclusion It is safe and efficient to hang the water at different heights during the operation of the disposable ureteroscopy to maintain low and safe IRP when using a UAS.