Irrigation systems evaluated for intrarenal pressure, flow rate

A study evaluating intrarenal pressure and flow rate with several different irrigation methods and other variables demonstrated that both larger ureteral access sheath size and working channel occupant are linked with reduced intrarenal pressure.¹

Intrarenal pressure was significantly higher when using a 11/13Fr ureteral access sheath compared with a 12/14Fr sheath (P < .01).

“We know that irrigation is vital in endourology to provide us with good visualization during the procedure, and pressurized irrigation is sometimes used to achieve that goal. However, by increasing flow rate that usually is followed by increasing intrarenal pressure, which has become of increased concern in recent years,” said Lucas B. Vergamini, MD, a research fellow at the University of Kansas Medical Center in Kansas City. Vergamini presented the findings at the 2024 American Urological Association Annual Meeting in San Antonio, Texas.

Boston Scientific recently released the LithoVue Elite flexible ureteroscope, which monitors intrarenal pressure. For the study, the investigators used the LithoVue Elite to report real-time intrarenal pressure and flow rate with several different irrigation systems in an ex vivo model of a porcine kidney/ureter. The Single-Action Pumping System (SAPS), Thermedx FluidSmart, and ENDOMAT were all used in the study.The automated pumps used pressures of 50 mmHg, 100 mmHg, and 150 mmHg, whereas the SAPS incorporated standardized movements applied by the same member of the research team. Working channel occupant options included none, a 200-µm laser fiber, a 365-µm laser fiber, and a 1.9Fr ZeroTip Nitinol Retrieval Basket. Ureteral access sheath options included none; an 11/13Fr, 36 cm; and an 12/14Fr, 36 cm. Different ureteroscopic settings were tested across all permutations of irrigation method, working channel use, and presence or absence of a ureteral access sheath, according to the authors. Eighty-four ureteroscopic settings were tested for a total of 252 experiments.

According to the authors, ENDOMAT had a higher intrarenal pressure than Thermedx at 50 mmHg and 100 mmHg. The SAPS had higher intrarenal pressure and flow rates than both ENDOMAT and Thermedx FluidSmart across ureteroscopic settings (P < .01). In addition, intrarenal pressure was significantly higher when using a 11/13Fr ureteral access sheath compared with a 12/14Fr sheath (P < .01).

“A strong positive correlation was seen between pressure set by the pump and both [intrarenal pressure] and [flow rate],” wrote the authors.

“We found that the SAPS is associated with higher intrarenal pressure and flow rate when compared to automated pumps. As we increase the diameter of the working channel…we see that there is a decrease in intrarenal pressure for the automated pumps and also a decrease of flow rate. We would also like to state that in any of those situations, neither automated pumps or SAPS ever reached mean intrarenal pressure over 30 mm of mercury, which is the threshold for pyelovenous backflow,” Vergamini said.

The authors concluded that live experiment models are necessary in order "to evaluate the impact of ureter contracture in [intrarenal pressure] and [flow rate]."

REFERENCE

1. Vergamini LB, Ito W, Tverye A, et al. Intrarenal pressure and flow rate profile using Lithovue Elite™: impact of different irrigation systems and working channel use. Presented at: 2024 American Urological Association Annual Meeting. May 3-6, San Antonio, Texas. MP43-10