Intrarenal pelvic pressure and renal temperature during 6.3Fr disposable digital flexible ureteroscope surgery: an in vitro experiment.

To investigate the dynamic changes of intrarenal pelvic pressure (IPP) and renal temperature during intracorporeal lithotripsy using a 6.3 Fr disposable digital flexible ureteroscope.An in vitro porcine kidney model was established with percutaneous puncture creating a 18 Fr peel-away sheath access to the upper, middle, and lower calyceal fornix.Standardized calcium oxalate stones were placed in the renal pelvis.A fiber optic temperature probe and pressure sensor were inserted via the sheath for synchronous monitoring of temperature and IPP.The entire system was maintained in a thermostatic water bath.A super-pulsed thulium fiber laser (wavelength 1940 nm, pulse energy 0.1 J, frequency 300 Hz, power 30 W) combined with a precision laboratory pump was used for lithotripsy through the 6.3 Fr ureteroscope.Normal saline (25 ± 1℃) was infused at irrigation rates ranging from 10 to 150 mL/min (increments of 10 mL/min).A senior urologist performed laser lithotripsy at the upper, middle, and lower calyceal fornices with the ureteroscope tip precisely positioned.The 150 μm laser fiber maintained a 1 mm working distance from the stone surface.Each 60-second lithotripsy session was repeated 5 times per parameter set.In the in vitro model, no significant differences in IPP dynamics were observed across upper, middle, or lower calyceal positions at varying irrigation rates (10–150 mL/min, P > 0.05). IPP increased linearly with irrigation rate: mean IPP reached 28.65 ± 0.93mmHg at 90 mL/min and exceeded the safety threshold at 31.23 ± 1.12 mmHg when irrigation rate increased to 100 mL/min.Conversely, renal temperature decreased with increasing irrigation rate: maximum temperature reached 45.1 °C at 20 mL/min and dropped to 40.9 °C (below safety threshold) at 30 mL/min.This study demonstrates that during RIRS using a 6.3 Fr disposable ureteroscope (non-UAS setting), maintaining irrigation rates between 30 and 90 mL/min ensures both IPP and renal temperature remain within safe thresholds, supporting safe and effective lithotripsy.