(UroToday.com) Leilane Glienke from the University of Michigan presented a study titled "Improved Control of Intrarenal Pressure Using a Prototype Fluid Management System Incorporating Ureteroscope Pressure Feedback" during the 38th Engineering and Urology Society (EUS) session. The study highlighted the importance of maintaining low intrarenal pressure (IRP) during ureteroscopy, emphasizing that elevated IRP can lead to pyelovenous backflow, increasing the risk of infectious complications and postoperative pain. Optimal IRP control requires continuous adjustment of irrigation rates throughout the procedure.
The investigators proposed a prototype fluid management system (pFMS) capable of automatically adjusting the irrigation rate based on real-time pressure feedback from the ureteroscope. The objective of the study was to evaluate the effectiveness of the pFMS in maintaining steady-state IRP below the critical threshold of 40 cmH₂O across a range of irrigation pressures and outflow resistance (ROUT) scenarios, compared to conventional pressurized irrigation.
A validated silicone kidney-ureter model was used for the experiments. A LithoVue™ Elite ureteroscope (Boston Scientific, Marlborough, MA) was inserted, with the tip positioned within the renal pelvis. Trials were conducted under two irrigation conditions: using the prototype FMS with an IRP limit set at 40 cmH₂O, and using conventional gravity-driven irrigation at pressures of 50, 75, 100, 125, and 150 cmH₂O. Customized catheters of varying diameters and lengths simulated five different outflow resistance scenarios, corresponding to ROUT values of 0.9, 2.0, 2.9, 4.0, and 4.9 cmH₂O/(mL/min). Intrarenal pressure was measured every four seconds, and flow rate was determined for each setting. All trials were performed in triplicate.
The results demonstrated that with conventional irrigation, IRP increased proportionally with higher irrigation pressures and greater outflow resistance. IRP frequently exceeded the 40 cmH₂O threshold at higher resistance settings, particularly at pressures of 100 cmH₂O and above. In contrast, the prototype FMS effectively maintained IRP below 40 cmH₂O across all resistance scenarios. For example, at a ROUT of 2.0 cmH₂O/(mL/min), IRP with both conventional 125 cmH₂O irrigation and the pFMS were comparable at approximately 37 cmH₂O. However, with higher ROUT values of 2.9, 4.0, and 4.9 cmH₂O/(mL/min), IRP with conventional irrigation rose sharply to 47, 57, and 60 cmH₂O, respectively, while IRP with the pFMS remained below 40 cmH₂O.
Flowrate trends were also evaluated. Under conventional pressurized irrigation, flow rate increased with higher irrigation pressures but decreased as outflow resistance increased. With the pFMS, flow rate also decreased consistently with increasing outflow resistance, but at the lowest resistance settings, flow rate with the pFMS was higher than with conventional irrigation.
In conclusion, the study demonstrated that the prototype FMS maintained mean IRP below the critical 40 cmH₂O threshold across a wide range of outflow resistance values, while conventional irrigation frequently exceeded safe pressure levels. Automated adjustment of irrigation based on real-time pressure feedback appears to be an effective method for controlling intrarenal pressure during ureteroscopy and may reduce the risk of infectious complications and postoperative pain.
There were no questions from the audience. The moderator agreed with the conclusions of Dr. Glienke’s study and emphasized the importance of maintaining constant intrarenal pressure during endoscopic surgeries.
Figure 1. Experimental Setup - LithoVue™ Elite ureteroscope (Boston Scientific, Marlborough, MA) inserted to the silicone kidney ureter model.
Figure 2. Intrarenal Pressure vs. Outflow Resistance
Figure 3. Flowrate vs. Outflow Resistance
Presented by: Leilane Glienke MD, Department of Urology and Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
Written by: Seyedamirvala Saadat B.S., Research Specialist at Department of Urology, University of California Irvine, @Val_Saadat on X during the 2025 American Urological Association (AUA) annual meeting held in Las Vegas, NV, Saturday, April 26 - Tuesday, April 29, 2025