Real-time IRP monitoring may redefine safety and scope of flexible ureteroscopy

The LithoVue Elite system was granted FDA 510(k) clearance in Febraury 2023,¹ and obtained CE Mark in Europe at the end of 2024.² As the first device with integrated real-time intrarenal pressure (IRP) monitoring, LithoVue Elite may enable urologists to manage larger or more complex stones with flexible ureteroscopy––a procedure traditionally limited to small- or medium-sized stones.

IRP monitoring has been gaining traction in the stone disease space in recent years, as increased IRP during the procedure has been thought to result in several complications for patients post-operatively. However, knowing exactly which levels of pressure result in complications for patients remains a challenge for surgeons.

Professor Andreas Skolarikos

In the following interview, Professor Andreas Skolarikos shares his experience conducting the the first surgery for kidney stones using the LithoVue Elite System and touches on the growing reliance on IRP monitoring during ureteroscopy. He also speculates on how the LithoVue System may allow urologists to develop data-informed decisions about pressure thresholds to maintain during the procedure.

Skolarikos is a professor of urology at National and Kapodistrian University of Athens in Greece as well as the chairmain of the European Association of Urology Urolithiasis Guidelines Panel.

Urology Times®: Given the increasing prevalence of kidney stones and the reliance on ureteroscopy, particularly for small- to medium-sized stones, how significant do you believe real-time intrarenal pressure monitoring is in improving patient outcomes and reducing complications?

Skolarikos: Intrarenal surgery means that we operate through the original orifice of the patient's body. We go up to the kidney from inside the ureter to [fragment] ureteral stones using increasing [laser energy.] A lot of urologists are using flexible ureteroscopes to disintegrate stones up to the kidney. One of the major disadvantages of this procedure is we work in the narrow anatomical space, and in order to see the stone and see inside the pelvicalyceal system of our patients, we need to give some irrigation, some fluid, to expand the cavity and have a good view inside the system to break the stone. This irrigation inevitably increases the pressure in a very closed system. Unfortunately, we believe that this increase of intrarenal pressure might cause problems to either the patient's kidney or the patient him/herself. [This may include] some bleeding, either intraoperatively or postoperatively, fever, and, of course, may cause also sepsis. Fortunately, the sepsis rate is not that high, but it is very important.

We [now] have the opportunity, incorporated in the new flexible ureteroscope Lithovue Elite coming from Boston Scientific, to measure actively, second by second, the pressure inside the system. We know how high we go, and we may be able, in the very near future, to stop the operation, empty the system from the fluid, reduce the pressure, and restart the operation again. That, we believe, will increase the stone-free rate of the patient, because it will manage the operation in a better way, and also decrease the incidence of bleeding, fever, and sepsis, either intraoperatively or post-operatively.

Urology Times: How does having access to real time intrarenal pressure data change your surgical technique or your decision-making during surgery?

Skolarikos: That is an excellent question. We have tested the LithoVue Elite in our first 2 patients in Europe. Now, we have [IRP information] as we operate with the LithoVue Elite system, and we can actually see not only the actual pressure inside the system, but also a signal when the pressure is higher than what we had set it up to prior to the operation. So, we know exactly when to stop. We expect that post-operative complications, fever and sepsis, or infectious complications will be reduced. We were always thinking that the intrarenal pressure was causing all these problems, [but] we were not sure how high the pressure [needed to be to] cause problems. It is a unique opportunity with the LithoVue Elite to measure the pressure and different cut-offs of pressure and see exactly above which cut-off the problem starts or the problem is created for our patients. This changes our surgical technique.

Up until now, flexible ureteroscopy has been conceived as a procedure limited to small- or moderate-[sized] renal stones. But if I know exactly what I'm doing during the operation, if I'm able to see how high the pressure is going, or to know exactly when to stop the operation, empty the kidney, reduce the pressure, and come back again, it will definitely give us the opportunity to increase the size of the stone that we'll be able to treat with the LithoVue Elite and with flexible ureteroscopy in general. We have to realize that the complication rate for flexible ureteroscopy is far less compared with percutaneous renal surgery.

Urology Times: As you mentioned, fluid irrigation is essential during this procedure, but it can increase intrarenal pressure. What specific thresholds do you consider critical during the procedure? How do you adjust irrigation parameters to maintain safe pressure levels?

Skolarikos: That is, again, an excellent question for 2 reasons. First of all, we know from [studies] that the intrarenal pressure should be as low as we can possibly achieve. The normal intrarenal pressure is approximately 10 cmH₂O to 12 cmH₂O. We know from [studies], as I said, that if I increase the intrarenal pressure above 40 cmH₂O, or even more above 80 cmH₂O, then the backflow of microbes of fluid inside the renal cortex and inside the circulation of the patient's body increases.

This is the beauty of the LithoVue Elite, [which has] an incorporated tip to measure the intrarenal pressure. We will be able to measure different cut-off levels and see in real practice which [level of] pressure is important to stay below. Nowadays, we make assumptions, because this is not very easy to know. We were relying mostly on experimental measurements and outcomes. Now, for the first time, is the opportunity to have real patient data to document if I go, let's say above 40 cmH₂O [and see if] something happens. If I go above 80 cmH₂O or above 120 cmH₂O in a very dilated system with a good accommodation or good compliance, is it feasible? And if it is feasible, does it cause any problems? This is a unique opportunity to adapt irrigation accordingly to what we see and to the results that we will have in the very near future.

Urology Times: How do you anticipate that consistent IRP monitoring during ureteroscopy will affect the incidence and severity of these complications in patients?

Skolarikos: Well, first of all, we have to realize that severe complications like sepsis—thanks to the experience of the urologic community—are not that high in percentage. It’s about 1% to 3%, but it could be a lethal complication. I think the advantage of the LithoVue Elite is to decrease the incidence and the severity of this complication.

Importantly, the number of patients [that need to be] treated [is increasing]. In the near future, I believe that because we will treat more patients with flexible ureteroscopy in general, the incidence of septic complications or infectious complications will also increase. [With] the LithoVue Elite and being able to measure the intrarenal pressure, these complications could be the end point and the outcome that will improve for our patients.

Urology Times: How does the combination of single-use technology and integrated IRP monitoring enhance safety and procedural efficacy?

Skolarikos: For many years, we used the single-use flexible ureteroscopes without being able to measure the intrarenal pressure. It is a safe procedure, but now and then, we have complications [such as] intrarenal bleeding that obstruct the view during the operation. If I have some intrarenal bleeding, unfortunately, I have to stop the operation, and I have to come back for a second session for my patients. The second complication is fever or renal damage, or even septic episodes. The LithoVue Elite, with the integrated intrarenal pressure monitoring, I strongly believe is the only opportunity that we have today to do a study on this and prove the advantage that the intrarenal pressure measurement gives to our patients in reducing the complication rate.

[It may improve] safety, but also the efficacy of the procedure. Why? Because it's not only further reducing a complication that is already low, it is giving the opportunity to the surgeon to operate in large stones for a longer operative period. [Right now], we have an operation limit. We say, "Do not stay inside the kidney for more than 1 hour to 90 minutes," because we have seen from major studies that increasing the operation time beyond 90 minutes increases the sepsis rate for the patient. But now, having an instrument [where] I know that for 1 and 1/2 hours or even more, my pressure is below the cut-off limit, this will give me the opportunity to become more efficient for my patient and increase the indications for flexible ureteroscopy.

Urology Times: Considering the complexities of individual patient anatomy and stone burden, how do you see this technology aiding personalized surgical approaches and optimizing outcomes for diverse patient profiles?

Skolarikos: The complications do not depend only on the surgeons, as a lot of people believe, but also on the stone and basic characteristics. In a difficult spider-like pelvicalyceal system, a system that cannot accommodate fluid quite well, [and] the compliance of the system is very low. Good compliance means [that] I'm giving some volume, but the pressure inside the system is remaining low. If I'm giving the same amount of volume of irrigation of fluid inside the system but the pressure goes very high, this is a poor compliance of the system. Nowadays, with the advantage of measuring the intrarenal pressure inside the system, the LithoVue Elite will [help] us understand the specific patients' anatomy together with a specific type of stone the patient has to orient to the individual patient.

The indications of flexible ureteroscopy will change in a better way, [because] we can also avoid some cases where the indication may not be quite correct. [For example], we can avoid treating patients in whom] the system is not very compliant to the irrigation, or the stone is located in a very tight and narrow space, and we anticipate a high pressure during the operation. Now, you will be able to measure it and know exactly when to stop or change the access to the kidney.

Urology Times: Beyond some of the immediate surgical benefits, what are your thoughts on the long-term implications of routine intrarenal pressure monitoring, particularly in terms of data collection, research, and the potential for developing standardized protocols to minimize these complications?

Skolarikos: As I said, this is, for the first time, a real opportunity to redo all the studies that we have made all these years about flexible ureteroscopy and intrarenal pressure. This will be real data on day-to-day cases. That means that we have the possibility and the ability now to actually plan a study, measure the cut off [at which] complications will occur, and accommodate them in the pelvicalyceal system. This is clinical research, meaning the outcomes of these studies will be of clinical use from the day 1, and this is very important. Now is the time to have real clinical data and change the knowledge that we have from [study] data with this real intrarenal pressure monitoring.

Again, we have to be very clear that the complication rate of flexible ureteroscopy in general is low, and it's due to the urologists and urological community, but also to the advancement of the technology that we have the past 10 to 15 years. But it's not only the complications—when we think of our patients, we will increase the indications of flexible ureteroscopy, and most importantly, we will be able, for the first time, to properly select the best candidate for intrarenal surgery with flexible ureteroscopy for ureteral stones, thanks to LithoVue Elite and to intrarenal pressure monitoring.

Urology Times: Is there anything else that you wanted to add?

Skolarikos: This is very important. Together with the intrarenal pressure, the incorporation of the same instrument [with the] ability to suction the fluid inside the system will change even further the way we treat our patients with stones inside the system.

REFERENCES

1. Boston Scientific receives FDA clearance for LithoVue Elite single-use digital flexible ureteroscope system. News release. Boston Scientific Corporation. February 3, 2023. Accessed May 15, 2025. https://news.bostonscientific.com/2023-02-03-Boston-Scientific-Receives-FDA-Clearance-for-LithoVue-TM-Elite-Single-Use-Digital-Flexible-Ureteroscope-System

2. What is ureteroscopy and how does it help in treating kidney stones? News release. Boston Scientific. December 3, 2024. Accessed May 15, 2025. https://news.bostonscientific.eu/what-is-ureteroscopy-and-how-does-it-help-in-treating-kidney-stones