Comparison of the safety of flexible ureteroscopy with the different irrigation methods in a 3D print kidney model.

Objective: To compare intrarenal pressure (IRP) and irrigation flow by varying suspended water heights and hand-held pressure pumping during flexible ureteroscopy using an in vitro 3D printed kidney model.

Methods: A 3D-printed silicone model was used to simulate the kidney. The ureteral access sheath(UAS) was connected to the kidney model and positioned at the ureteropelvic junction. Central venous pressure tubing was used to monitor the pressure in the renal pelvis under different conditions. Sheath sizes of 12Fr and 14Fr were tested with flexible ureteroscope (fURS) sizes of 7.5, 8.5, and 9.5Fr, respectively. The irrigation was gravity-based, with suspended water heights set at 60, 90, 120, 150, and 180 cm. The manual pumping as another set of measurement is used to measure the maximum intrarenal pressure.

Results: Using a 12Fr sheath with a 9.5Fr fURS loading without additional accessories resulted in IRP ranging from 8.4 to 17.5 cmH2O, while manual pumping perfusion pressure exceeded 60 cmH2O. Loading a 200-um laser fiber reduced the pressure to 6.4-10.5 cmH2O, and using a stone basket decreased it to 4.0-5.0 cmH2O. Using a 14Fr sheath with a 9.5Fr fURS resulted in an IRP of 2.5-6.0 cmH2O, compared to 17 cmH2O with manual pumping. With a 12Fr sheath and a 7.5Fr fURS, the IRP ranged from 5.4 to 8.2 cmH2O, while manual pumping resulted in 25.5 cmH2O. With a 14Fr sheath and a 7.5Fr fURS, the IRP ranged from 1.5 to 4.3 cmH2O, and manual pumping resulted in 9.0 cmH2O.

Conclusion: When using a UAS in a flexible ureteroscopy, the IRP can be maintained within a safe range with different fURS/UAS combos with a suspended water height of less than 180 cm. However, with specific fURS/UAS(9.5Fr/12Fr) combos, the IRP exceeded the safe limit when using manual pumping. Gravity irrigation with a suspended water height of less than 180 cm is safe in this simulated clinical environment.