Novel irrigation pump for indirect intrarenal pressure measurement during flexible ureterorenoscopy

Purpose: Flexible ureterorenoscopy (fURS) with laser lithotripsy is known to produce elevated intrarenal pressures (IRP), which can lead to complications. While direct IRP monitoring methods exist, they are not widely used in clinical practice. Indirect IRP estimation by application of the Hagen-Poiseuille equation has been proposed as a viable alternative. This study aims to develop and validate a novel irrigation pump capable of estimating IRP in real-time during fURS. The estimated IRP will be compared with the actual measured IRP on a phantom kidney. Materials and methods: An irrigation pump was designed with flow rate control based on pressure sensors. The Hagen-Poiseuille equation was applied to estimate IRP from the proximal pump pressure and the pressure drop across the tubing and fURS. A phantom kidney model was used to simulate human renal conditions. The pump was calibrated at three flow rates (20, 30, and 40 mL/min), and IRP was estimated in real-time during irrigation. The correlation between this inferred IRP and the actual IRP was assessed using the Pearson correlation coefficient. Results: A strong positive correlation was found between inferred and real IRP values at all flow rates. At 20 mL/min, the correlation coefficient (r²) was 0.98 ( P < 0.001); at 30 mL/min, r² was 0.99 ( P < 0.001); and at 40 mL/min, r² was 0.98 ( P < 0.001). Additionally, the mean difference between estimated and real IRP at 30 mL/min when a 230-µm laser fibre was used in the ureteroscope was 4.77 cmH 2 O. Conclusion: The described irrigation pump provides, in the in vitro setting, an effective method for estimating IRP during fURS by using real-time proximal pressure measurements. This non-invasive indirect approach to IRP measurement could improve patient safety by ensuring that IRP remains within safe limits, potentially reducing complications associated with elevated pressures during flexible ureterorenoscopy.