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BackTable / Urology / Article
Laser Kidney Stone Removal 101: Laser Types, Energy Settings & Fiber Sizes
Melissa Malena • Updated Jul 18, 2024 • 108 hits
Laser technologies have helped to make the surgical removal of kidney stones more efficient than ever before. However, operators require an understanding of laser types, energy settings, and other equipment parameters to be effective with laser stone removal. Director of Clinical Research at the Stone Center at Vancouver General Hospital, Dr. Ben Chew, shares his recommendations for successful laser treatment of kidney stones, covering the technical elements of laser devices.
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 Holmium:YAG laser excels in thorough fragmentation of stubborn kidney stones, but exhibits high retropulsion rates.
• The Thulium Fiber laser utilizes Moses technology to decrease retropulsion, but can provide inefficient stone fragmentation, increasing the heat burden on the kidney.
• The maximum wattage of laser energy should not significantly extend over 10 watts in the ureter and 20 watts in the kidney.
• Fiber size recommendations vary based on the location of the kidney stone, with the smallest fibers being used in the kidney and the largest used in the bladder.
Table of Contents
(1) Types of Kidney Stone Lasers: Holmium:YAG vs Thulium Fiber
(2) Kidney Stone Laser Energy Settings
(3) Kidney Stone Laser Fiber Sizes
Types of Kidney Stone Lasers: Holmium:YAG vs Thulium Fiber
The Holmium:YAG laser has long been the gold standard laser technology for the surgical treatment of kidney stones. Despite the Holmium:YAG laser's ability to efficiently fragment stones, the Holmium:YAG laser possesses a high peak power and retropulsion rate. According to Dr. Chew, the combination of power and retropulsion often moves the stones around, particularly in the ureter.
The Holmium:YAG laser was followed by the thulium fiber laser which featured Moses technology. Moses technology features a first pulse sent by the laser followed by a second laser pulse that hits the stone and delivers more effective fragmentation. This approach decreases retropulsion rates, but can sometimes prove inefficient in fragmentation of stubborn stones. Dr. Chew recommends utilizing both lasers in a case dependent fashion, as they both offer advantages and disadvantages in different clinical scenarios.
[Dr. Ben Chew]
There's the Holmium:YAG, which is still the proven gold standard, probably the most popular one across the world, made by multiple different companies. It's the tried and true that we've had. The newer ones that have come out, the reason why the Holmium:YAG, they first had to develop pulse lasers. When it was continuous, it would just generate so much heat, it would basically damage the kidney.
It wasn't until they could pulse the lasers that they could use it clinically. Once they developed that, they found that it fragmented stones really well. This is still the go-to in many, many different places. Now the second laser that I used was only a few years ago, and that was a thulium fiber laser. With that, when the engineers come to the OR, I think this is when we really bridge the gap because we as urologists, we're really problem solvers and we know how to troubleshoot.
When the engineers are in there, they say, "Well, why do you do this? Why do you do that?" It's because we're compensating for what instruments we're given. We're compensating for the fact that Holmium:YAG, although it breaks up stones quite well, has a very high peak power and there's a lot of retropulsion. The stones can move a lot, particularly in the ureter. Then it also breaks it up into big fragments. That's why there were all these studies done on dusting versus fragmenting and what's better? Is it better to basket all the stones out and fragment them, or is it better to dust them all?
I think that sometimes we don't know what we need until it comes along because we are so used to problem solving, at getting around things. Thulium fiber came out and I think that was a really big difference. I think a lot of people have noticed that they've been able to tackle bigger stones. There's been less retropulsion. That's been the biggest thing. Then of course, Holmium: YAG also underwent a modification as well, too.
That's with the Moses technology. Where essentially you're shooting out one pulse first to part the waters like Moses did, and then the second pulse goes and actually hits the stone so that you get more effective fragmentation on that stone. There's two different ways of doing that, and they're supposed to produce more dust. That's what we're looking at right now. There are even newer ones out there as well, too, like the Thulio laser. The thulium fiber laser is the one I've been working with, Olympus, the saltive laser.
We have that one. We also have the regular Holmium:YAG. We have a 30 watt, which is very inexpensive and a bit of a workhorse. Then we also have the Lumenis P120, which of course has the Moses technology with it as well, too. There's a multitude of lasers you can use and like I said, I don't know much about the new Thulio laser, but that's what we have. Probably the biggest question I get whenever I go to a conference or whenever I'm speaking about this is, "Hey, Ben, what laser should I buy?"
Let me cut to the end right here and tell you which one to buy. It depends. I must admit that I do have consulting agreements with those companies, so it's not because of that. I must tell you, though, it was all Holmium:YAG and then thulium fiber came along. We were dusting everything. It was really great. Then after about three years of using just total pure thulium fiber, I now realize when it's good to use Holmium:YAG and when you need it.
My answer, because I'm spoiled and I get to have both, I like actually having both. I think depending on what you want to do, where the stone is, you probably need a bit of both lasers. In that aspect, too, then that probably means that you're probably okay with either of those lasers, either Holmium:YAG with Moses or thulium fiber. I think that's what the main story is. If you really want to make yourself efficient, it's really nice to have a bit of both.
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Kidney Stone Laser Energy Settings
Different laser energy settings are required when treating a urethral stone compared to a kidney stone. In the ureter, Dr. Chew cautions against going above 10 watts as it can cause heat damage. If higher wattage is needed, it must be utilized sparingly and with constant cold water irrigation to avoid burns.
In the kidney, the top wattage recommendation increases to around 20 watts with room temperature irrigation and pauses every 30 seconds. For stubborn stones in the kidney, the energy can be increased to 30 watts cautiously when paired with an access sheath and constant, cold irrigation.
Dr. Chew recommends the Holmium: YAG laser at the 0.6 setting for stone fragmentation. For stone dusting, Dr. Chew advises utilizing the thulium fiber laser due to its pulse width and hemostasis benefits.
[Dr. Jose Silva]
Let's talk about energy in terms of settings. Let's start with the whole Holmium. What are your usual go-to settings for a urethral stone versus a kidney stone?
[Dr. Ben Chew]
Great question and I think there's no one right answer for this. The one thing I would caution we always are talking to the residents about is just making sure that your max wattage in the ureter is around 10 watts. It doesn't mean you can't go over 10 watts but 10 watts, we want to keep it below that no matter what laser you're using because energy is energy. The constant basically is that when you put enough laser energy in there it takes this much energy to take one degree Celsius of one cubic centimeter of water.
That constant is the same for no matter what laser you use. We want to keep it around 10 watts or under for the ureter. If you go up a little higher just use it very sparingly. Make sure you have cold irrigation going and don't turn your irrigation off. We used to do this with Holmium:YAG because the stone would move so we turn our irrigation off, hit the stone because we wouldn't want it to retropulse and that will allow that fluid to really heat up. If you heat it up too much you can damage the ureter. This can be a stricture whether using Holmium, thulium fiber, thulium YAG, all these things.
Really it's 10 watts in the ureter and about 20 watts in the kidney. You can go up to 30 with caution, over 30 a little bit with caution but again access sheath, cold irrigation. We used to use warm irrigation to patient temperature 37. We now use just room temperature irrigation between 20 to 22 degrees Celsius and never turn it off just to keep it going and then pause every 30 seconds or so.
Guillaume Parik has done a study in a pig looking at how long you can actually laser until the temperature starts to go up. This is in a pig so it's a little different, but he measured it to be around three and a half minutes where you can laser continuously. I generally leave that a little bit shorter because besides that one study we don't really know and I tend to go about 30 to 45 seconds give it a 5 to 10 second pause.
It also lets a lot of the dust clear up too so you can see better, see if we're missing any pieces, and then go from there. My first thing is the safety is 10 watts in the ureter, 20 watts in the kidney, up to 30 watts with caution and in the ureter 10 watts, and maybe 15 watts with caution. Again really the important part is keep it cool, keep it running and I think it depends on what you want to do. With Holmium:YAG if you're going to fragment the 0.6 and 6 works really well and that's only 3.6 watts you can really keep hitting that for a long time without having to raise the temperature quite a bit.
0.6 and 6 for Holmium works really great. If it's a harder stone you might want to turn it up a little bit. 1 and 10 seems to work really well 1 joule and 10 hertz. I'm not sure what ones you like Jose for the Holmium.
[Dr. Jose Silva]
Yes, usually 0.8 and so I usually go about 6 watts in the ureter which is 0.8 and 8, something like that but essentially this is what happens. The delays that I have is the Lumenis, but recently it got damaged and we got a loan that it was actually the thulium. We went through a vendor and then I don't know if the rep just puts the setting that just to completely blast, obliterate the stones so I was doing higher watts in the ureter and it was just because of the settings that I was provided because I had no idea on what settings to use. Definitely I saw a big difference in terms of how fast the thulium was blasting those stones.
Now that I got the Lumenis back I'm starting to crank up the watts to see how much to actually have a fairground and actually have a good comparison between one or the other but like you mentioned I don't see the same dusting capacity between one or the other definitely it breaks them very good and I don't have any issues but it is different.
[Dr. Ben Chew]
I think Holmium:YAG is good for fragmentation which is what I use it for and then the thulium fiber is good for dusting and you asked too about the settings and so 6 watts on a Holmium:YAG versus six watts on a thulium fiber really you just cannot compare. It's not like you're going 60 miles an hour in a Ford versus 60 miles an hour in a Honda, it's different.
It's really because of the way the peak profiles are, because of the way the laser beam is and everything, it really is quite different. The only thing you can tell about that is that because it's watts and because that's a physics constant, the only thing you can tell is that that's going to be a similar way to basically get the heat. It's really nothing else and it's all different. If you're going to do 0.6 and 6 on thulium fiber, it's quite different.
When you first get it, I think the first thing you're struck by is that you've had this laser for decades, this other laser we are used to, what do I set this to? Then there are literally thousands of settings because it goes up to 2400 Hertz you can go down to 0.025. Let me give you my readings on thulium fiber. I know it can go down to 0.025 and you have three settings on the pulse width.
Pulse width is the length of time it takes to deliver the energy. A short pulse width is like a short jab from a boxer. A medium pulse width and longer pulse width is the same energy but delivered over a longer time. If that boxer is going to hit that bag with the same energy but over a longer time it's not going to move back as far. That's why a longer pulse width is supposed to do two things.
One of them, decrease retropulsion and also if you're dealing with a blood vessel it's supposed to help with coagulation and hemostasis. If you're doing hemostasis with it it's better to put it on a long pulse width because then it is just basically able to coagulate better. However, I find that the shortest pulse width of thulium fiber is still longer than the longest pulse width of Holmium:YAG.
Even if you take your P120 and change the pulse width, it's still longer with the thulium fiber. That means that you're going to get, remember with longer pulse width you're going to get less retropulsion, it's not going to move. It's also going to make it into finer pieces of dust just because of the way the wavelength is. That's one thing and the wavelength of thulium fiber is much closer to the absorption of hemoglobin and water than Holmium is.
Thulium is going to be better for hemostasis because it is better absorbed by hemoglobin.
Kidney Stone Laser Fiber Sizes
According to Dr. Chew, fiber size decisions should be made based on the position and location of the target stone. For bladder stones targeted by thulium fiber nucleation or a hole-up approach, the recommended fiber size is 550 microns. When working in the kidney, the recommended fiber size is 150-200 microns, depending on device type. If the procedure is solely in the ureter, a semi-rigid ureteroscope and larger fiber, ranging from 365 to 400 microns is acceptable. However, if working in the ureter and the kidney, the smaller 150-200 micron fiber should be used throughout.
[Dr. Jose Silva]
Going back to the kidney stones, in terms of fiber size, how do you decide what fiber to use? Is it a matter of the size of the stone? Is it a matter of flow, having good flow versus good visualization? How do you determine what to use?
[Dr. Ben Chew]
For bladder stones, if you're going to be doing a hole-up or a thulium fiber nucleation, then you're going to be using a 550 anyways and you would just use the same fiber. If you're just doing a bladder stone, probably a 550 is good for the bladder. For the ureter and the kidney, this goes for both the thulium fiber and the Holmium. If you're going to be working in both the ureter and the kidney, I always just end up using the smaller fiber in the ureter because I know I'm going to be going up to the kidney anyways.
If you're up in the kidney, you should always use the smaller fiber, a 200 micron, or if you're using thulium fiber, 150 micron, just because it's smaller. Therefore, in your working channel, you're able to get more flow through there and you also get better flexibility if you're going to go into the lower pole. If you're just in the lower ureter and using a semi-rigid ureteroscope, a 365 or 400-micron fiber is fine, because it's easier to handle, and you get lots of flow anyways, so that would be fine.
If there's any chance of you going up into the kidney, I would just switch to the smaller fiber. It can move around a little more in the semi-rigid ureteroscope, but at least you're using less product and you can use this one in both the kidney and in the ureter as well, too.
[Dr. Jose Silva]
Yes, that's usually what I do. If I think I'm going to go to the kidney, I just start with the 200. If not, I use the 365, and it has worked fine.
Podcast Contributors
Dr. Ben Chew
Dr. Ben Chew is a urologist at University of Britich Columbia and the chair of research of the Endourology Society.
Dr. Jose Silva
Dr. Jose Silva is a board certified urologist practicing in Central Florida.
Cite This Podcast
BackTable, LLC (Producer). (2024, February 20). Ep. 152 – Laser Options for Kidney Stones: A Clinician’s Guide [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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