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BackTable / Urology / Article
The RetroPerc Access Kit for Retrograde Percutaneous Nephrolithotomy
Kaitlin Sheppard • Updated Apr 1, 2025 • 32 hits
The RetroPerc Access Kit offers a structured and streamlined approach to retrograde percutaneous nephrolithotomy (PCNL), aiming to improve access consistency and reduce trauma through guided visualization and a standardized wire exchange process. This method can be especially helpful in complex cases, such as staghorn calculi, where scope stability and precise alignment are critical. In this article, urologist Dr. Jason Wynberg explains the role of the RetroPerc Access Kit, offering practical insights into his technique, case selection, and the value of hands-on training for procedural success.
This article features excerpts from the BackTable Urology Podcast. We’ve provided the highlight reel in this article, but you can listen to the full podcast below.
The BackTable Urology Brief
• The RetroPerc Access Kit standardizes retrograde PCNL, enabling precise, controlled renal access with minimal trauma.
• The kit includes a sharp puncture wire with a protective sheath and a coaxial micro introducer to facilitate smooth wire exchanges while maintaining tract stability. The puncture wire is exchanged for a sensor wire through a coaxial catheter to maintain access before tract dilation.
• The system reduces the need for repositioning, streamlining workflow and improving efficiency in supine PCNL.
• Preoperative CT planning guides patient positioning, ensuring alignment with the infundibulum for an optimized puncture trajectory.
• Proctoring, case observations, and peer-to-peer learning are valuable for urologists integrating the RetroPerc system into their practice.
Table of Contents
(1) Design of the RetroPerc Access Kit
(2) From Concept to Clinical Use: The Evolution of the Retroperc Access Kit
Design of the RetroPerc Access Kit
Dr. Jason Wynberg developed the Retroperc Access Kit to refine retrograde percutaneous nephrolithotomy (PCNL), providing a controlled and reproducible method for renal access. The kit includes a sharp puncture wire with a protective sheath to prevent ureteroscope damage and a coaxial micro introducer that facilitates smooth wire exchanges while maintaining tract stability. This system is particularly useful in cases involving large or staghorn stones, where traditional access can be challenging.
Inspired by a need for a more reliable alternative to antegrade access, Dr. Wynberg revisited historical techniques, adapting and modernizing an overlooked approach first described by Dr. Larry Munch in 1989. By integrating these principles with contemporary instrumentation, the Retroperc Access Kit aims to improve safety, procedural efficiency, and adaptability in complex stone disease management.
[Dr. Jose Silva]:
I understand that you develop a system for this and you have a trademark patent going on. Is that what you're using right now?
[Dr. Jason Wynberg]:
It is. NYU was kind enough to allow me to use this product in my practice.
[Dr. Jose Silva]:
Your kit, it includes also the dilators, or it is just the puncture until you have an endo wire there?
[Dr. Jason Wynberg]:
It includes the sharp puncture wire and the sheath that protects the wire, so it doesn't damage your scope. It also includes what's called a coaxial micro introducer, which is basically, a 30-centimeter long 5.0 French, it's almost like a vascular catheter with an inner dilator that tapers right down to the puncture wire. The purpose of that coaxial micro introducer is simply to allow you to remove your puncture wire in favor of an 035 or 038 endourology wire while maintaining the track that you've created.
The kit includes those two items, and whichever endourology wire or sensor wire or any wire, frankly, you can pass that through the outer catheter at the flank once you remove the puncture wire and the inner dilator from a coaxial catheter. It's hard to describe it verbally. You almost have to see a video and then it makes sense.
[Dr. Jose Silva]:
No. Definitely, you create a great picture of going in through the kidney. For patients that have big stones, does it matter? When I say big stones, if you cannot pass the ureteroscope all the way into the calyx.
[Dr. Jason Wynberg]:
I would say that 9 out of 10 of those cases, if you look at the calyx that's at the end of those big stones, 9 times out of the 10, the calyx is collapsed around the stone, which means that the urine that's produced is draining. When you don't have hydronephrosis or dilated calyces, then almost always with a pressure bag, your flexible ureteroscope will get a sufficient distension to allow you to drive right beside the stone to the papilla.
9 times out of 10, big stones, cast stones, staghorn stones are not only not more difficult, but there's even an advantage that people have experienced. That is that if you have a very hydronephrotic kidney, the intrarenal anatomy is a little less supportive of the ureteroscope if it's very dilated. As you advance the wire, the ureteroscope can push back a little bit until it meets some renal architecture that will support it.
If you have a big stone there, like a staghorn, once you position yourself in your chosen papilla, the stone provides tremendous support for the scope. The puncture actually becomes easier than you might think, becomes a very easy puncture. Staghorn stones, in general, are a favorable finding for this. Now, of course, if you have very dilated calyces showing that it's truly a very obstructive stone, then it's possible you have to laser just to get past it, but that's not very much lasering. It's not to disrupt the stone, it's just to allow you to advance your scope.
[Dr. Jose Silva]:
Sometimes with those big stones, even through the antegrade axis, it can be challenging. The wire might not go in, it might just stay in the same calyx, it might not go down to the ureter. I understand what you're saying. How you said, "Okay, I'm going to develop a system." How did that happen?
[Dr. Jason Wynberg]:
Thank you, Dr. Silva. The same evening that I failed in my antegrade PCNL, the patient was fine, but I wasn't used to waking up a patient and apologizing for a procedure that didn't happen. I was in my office, I think everyone had left, and I was just recalling my residency. I guess, different thoughts and ideas were coming and the idea of putting it through a ureteroscope came to me.
From there I called the rep for the Cook Lawson puncture set and took out their wire and it did manage to emerge from the ureteroscope. Then I knew I had a real idea. What's very interesting, Dr. Silva, is that in 1989, Dr. Larry Munch actually published that very same procedure of putting a retrograde puncture wire through a flexible ureteroscope. That was a paper in the Journal of Endourology.
What's interesting was PubMed was not indexing the Journal of Endourology at that time. To this very day, if you know the reference for the paper, you can order it through your library, but if you go into PubMed, I believe it will not pull up. His innovation in 1989 was lost to the urologic community for many, many years. What's also interesting is at the same time that, at the Detroit Medical Center we were doing an IRB on this idea, there's a Dr. Kawahara in Japan who was doing this exact same thing. Dr. Kawahara from Yokohama, Japan, at the same time we were publishing the same surgical modification of the old concepts.
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From Concept to Clinical Use: The Evolution of the Retroperc Access Kit
Dr. Wynberg shares his approach to deploying the RetroPerc Access Kit, highlighting both the technical steps and the learning curve involved. He walks through his method for wire deployment under ureteroscopic guidance, capturing the puncture wire at the flank, and using a coaxial catheter to facilitate wire exchange. Dr. Wynberg also offers practical advice for early adopters—such as using a disposable scope during initial cases to reduce the risk of damage—while emphasizing the importance of CT-based planning and maintaining scope stability throughout the process.
[Dr. Jose Silva]:
Let's go back to the retrograde procedure. You mentioned you have an access sheath. What size do you use?
[Dr. Jason Wynberg]:
Well, the kit comes in a fixed size. Are you asking what the dimensions of the kit are?
[Dr. Jose Silva]:
No, no. The access sheet per se.
[Dr. Jason Wynberg]:
The ureteral access sheath?
[Dr. Jose Silva]:
The ureteral access sheath, yes.
[Dr. Jason Wynberg]:
I think that's similar to ureteroscopy for all practitioners. Some use 1113, some 1214. It depends on whether the patient's been pre-stented. Are you asking about length?
[Dr. Jose Silva]:
It doesn't matter. Your kit doesn't matter whether you have the 1214 or the 1113.
[Dr. Jason Wynberg]:
No, no, it doesn't matter.
[Dr. Jose Silva]:
What ureteroscope do you use?
[Dr. Jason Wynberg]:
It can be used with any ureteroscope, although there is a learning curve of a few cases. During your learning curve, it would be wise not to use a $20,000 high def digital ureteroscope because while you're getting a feel for how the wire is handled, it is possible to make a handling error and effectively deploy the puncture wire inside your working channel and your scope will fail the leak test if you do that. After you get a feel for how the product is used after a few cases, the risk of that happening goes way down. A disposable ureteroscope is just a good decision for this procedure.
[Dr. Jose Silva]:
Once you get the puncture wire out, then you said that you advance an access sheath.
[Dr. Jason Wynberg]:
Once the puncture wire comes out, it's a wonderful euphoric feeling. It's a great feeling. What you see is the skin tenting. We typically mark the posterior axillary line and the 12th or the 11th rib. You can see when your puncture wire comes out below the rib and behind the posterior axillary line, it's a very wonderful feeling. What you see is the skin tenting. You use an 11-blade to incise the skin and capture the wire. At that moment, what's good practice is to pause and go through your CAT scan.
Now of course, if you know your anatomy, if you've already programmed your mind, you already know what you have and safe, but it's not a bad idea. You have all the time in the world. You just go and take a look, and you scroll down your CAT scan. You can see your puncture on the CAT scan, but once you've decided that it's a perfect puncture, then you're done. You created your nephrostomy tracts. Theoretically, you could advance your balloon right over that wire because you have your track, of course.
Because we prefer-- I use a sensor wire. I prefer a sensor wire. We use a catheter at the flank to exchange it. This catheter is loaded over the wire at the flank. You draw out puncture wire about 30 centimeters just with your hand, gently. The ureteroscope is still at the papilla. There's no real danger. You're just pulling it through the ureteroscope at the papilla out the flank, so it's very safe. Then you load this coaxial catheter over the puncture wire that's out the skin.
Then you clamp both ends of the puncture wire at the back end of the coaxial catheter at the flank, just so that you have control over things and the wire that's still above the import of the ureteroscope, so that you're not going to pull your wire out, basically. Then essentially you advance your coaxial while you bring the ureteroscope down. Then what you have is your coaxial catheter goes horizontally in the kidney.
It curves down the UPJ and ends inside the ureteral access sheath, so that when you take out your dilator and your ureteroscope, what you have are two things left inside the patient, your ureteral access sheath and the coaxial catheter making a right-angle turn down the order into the upper third of the ureteral access sheath. When you put your new wire in at the side, it's channeled through and comes out the urethral side of the ureteral access sheath. Then you have through-and-through access.
[Dr. Jose Silva]:
Then is the patient at some point prone after this or you use the PERC, same position?
[Dr. Jason Wynberg]:
Same position. It's a single position. It works great. Regarding the position, if you look at your CAT scan and you plan your puncture on your CAT scan, imagine you have an underrotated kidney. Let's say, for example, you have an obese patient and there's a lot of perinephric fat. As you know, sometimes the kidney is a little less rotated posteriorally, it's a little more horizontal, just slightly. Then you know that because your puncture is going to follow the infundibulae, infundibular long axis, you can know exactly where it's going to come out. In a case where you have an underrotated kidney, your puncture wire will come out less posteriorly. When you position the patient, you need to boost them up, boost up their hips and their shoulders less.
Conversely, if you have a very overrotated kidney, for example, in a patient with very little perinephric fat, a very low BMI, sometimes you see that, then you may have to boost their hips and their shoulders a little bit more or slide them to the side of the bed. Once you plan your puncture and your position based on the CAT scan, you don't have to reposition. You almost imagine a three-dimensional box of your working space on the flank skin, and so long as you have the right angles to get to your stone, then there's no need to reposition.
Podcast Contributors
Dr. Jason Wynberg
Dr. Jason Wynberg is the director of endourology at NYU Langone Health in Brooklyn, New York
Dr. Jose Silva
Dr. Jose Silva is a board certified urologist practicing in Central Florida.
Cite This Podcast
BackTable, LLC (Producer). (2023, March 1). Ep. 84 – Novel Approach to PCNLs [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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