Surgeon: Dr. John D. Denstedt, M.D.
Dr. John Denstedt is the Secretary of the AUA and a pioneer in the area of lasers in kidney stone disease. Please join him in discussing laser technology and flexible ureteroscopy in this Masterclass

Moderator: Dr. Ben H. Chew, M.D.
Dr. Ben Chew is the Chair of Research for the Endourology Society and former fellow of Dr. John Denstedt. Please join us in discussing laser and flexible ureteroscopy technologies.

 

Webinar Transcript

Dr. Ben Chew:

Good morning, good afternoon. Thank you very much for joining us to our very first webinar. This is from the Endourology Society, and this is a new online education initiative started by Dr. Adrian Joyce, our chair of education, and also with Dr. Brian Matlaga, who is also the associate chair of education for the Endo Society. Thank you for joining us and thank you for coming with us. We're going to have a whole slate of education online. Please check out the website to actually look and see what our content is as well as our registration for it. It's all free right now, and what we'd like to do is ... Basically, it's going to continue on. This is not just a COVID thing, this is going to be for continuation. I think Dr. Joyce had basically planned this for quite some time now, and I think we just got spurred because of the extra time we had to get things going during this COVID time.

Dr. Ben Chew:

I am Ben Chew. I am the chair of research for the Endourology Society. I am an endo urologist here in Vancouver, British Columbia, in University of British Columbia-Vancouver. I basically have done my fellowship with Dr. John Denstedt. It's my pleasure to basically interview him today and talk about flexible ureteroscopy and laser lithotripsy. He really needs no introduction. He has been the treasurer of the Endourology Society for some time but has basically stepped back from that role to currently take on his current role as the AUA secretary. So, he's quite busy now and, as you know, was one of the first pioneers to use laser lithotripsy in ureteroscopy.

Dr. Ben Chew:

What we're going to do today is we're going to talk and show some video cases that Dr. Denstedt has done. I'm going to field questions. Please use the Q & A function that is on your webinar part there. That will pop up to us, and I can ask him at the appropriate times. Also, at the very end in terms of CME, what you're also going to notice too is that you will receive a survey from Michelle Paoli at the end of the month asking you which ones you have attended. Also, immediately after this webinar, when you finish, it will take you to a survey questionnaire, which, of course, we need for CME, and which you need to fill out too in order to get your CME. So, please fill out that attendance certificate and make sure ... That's really important. You will get one hour of AMA-approved credit for this. Let me just share this here.

Dr. Ben Chew:

Without any further questions, what I'd like to do is introduce Dr. John Denstedt, who we all know. We're just going to get started on the video, if that's okay with you, Dr. Denstedt?

Dr. John Denstedt:

Yeah. That's great, Ben. Can you hear me okay there?

Dr. Ben Chew:

Yep, absolutely.

Dr. John Denstedt:

Great. Let me just say before we start here, I think this is a great initiative by the Endo Society, which has always led the way in many, many things, as we all know. I just congratulate Adrian, Brian, and the whole team for pulling this together. I think it's just a great initiative. I'll also say this is quite a difficult time in the world, really, for all of us. Our hospital here is still pretty well closed down for elective surgery and so forth. We hope there's going to be a reopening in the next couple of weeks. We certainly hope so, but it's a difficult time.

Dr. John Denstedt:

On the other hand, I think we're all learning a lot as well. This is a good example of it, this webinar, virtual education we're going to hear a lot more about it, I'm sure with our various meetings over the next little while. Great initiative, excited to be here, and looking forward to talking to everybody. I understand we've got several hundred people registered for this, which is amazing really to see that level of interest, so if you want to get going Ben, if that's all right, [crosstalk 00:06:52].

Dr. Ben Chew:

That's great. Thank you. Actually, so 624 p;eope registered as of this morning just before we logged in, and also maybe you can give a plug for the AUA online as well too, Dr. Denstedt, when that will be.

Dr. John Denstedt:

Okay, well, thanks for that, Ben. As everybody knows, our in-person meeting which was scheduled in Washington, D.C., was supposed to happen in a couple of weeks for now, obviously was canceled, as have most other meetings, met with the same fate here of cancellation or rescheduling and so forth. We have actually bene able to salvage the vast majority of the AUA meetings. The plenary will happen virtual event of the end of June. It will be a two day affair over the weekend, Saturday, Sunday, June what is it?

Dr. Ben Chew:

27th and 28th.

Dr. John Denstedt:

28th, yeah. We're pre-recording and actually 165 faculty, and it happened immediately, stepped up to support that initiative, so just an incredible response. As well, we're going to have the posters, podiums, we have at least 1,800 of those were submitted by the deadline, and those will all go live within the next couple of weeks. So, we've been pretty successful in getting most of the signs there for the AUA meeting, and we hope people will sign in, take advantage of that as well. So thanks for that, Ben.

Dr. Ben Chew:

Yeah, no problem. And that's free too. Correct? There's no-

Dr. John Denstedt:

It's free for members of the AUA, right.

Dr. Ben Chew:

Great. So actually, before we get started on this, one of the ... I just launched a poll that people can answer that, and one of the questions that we've come up with is what actually criteria do you actually determine for ureteroscopy versus PCNL in upper ureteric stones?

Dr. Ben Chew:

So Dr. Denstedt, if there was a larger stone in the proximal ureter, when do you decide to do ureteroscopy versus a PCNL?

Dr. John Denstedt:

Yes, so you say a meatus proximal ureter, Ben, in your question here. I think it's renal pelvis, so let's so it's a renal pelvic stone. My sort of rough limit for a retrograde approach is typically one and a half to two centimeters at the most, which fits with the guidelines, of course, AUA, EAU guidelines for treating small stones bigger than two centimeters, I'd usually do a PCNL. The exceptions for that would be a special groups of patients, like those on anticoagulants, those who were very obese, multiple medical comorbidities, where you might want to extend that two centimeters to a little bit larger stone to treat on a retrograde fashion.

Dr. John Denstedt:

So with those populations, I might consider ureteroscopy as an alternative to purge. I think the practical point, what I do anyway, if I have a patient like that with a larger stone, I'm going to approach ureteroscopically, I would typically tell them or warn them of the possibility of the stage procedure. We're going to try to do the whole thing in one treatment, but there might be a limit here. I tend to limit my ureteroscopies to about 90 minutes at the most. And there's a chance that will have to be staged. I think that's only 10 to 15% of all these cases, usually, but I just tell them all about that could end up staged.

Dr. Ben Chew:

Great, thank you. Well let's get started on the video, because you've got some great cases to show us here. And just let me know when you want me to pause.

Dr. John Denstedt:

Sure, Ben. Let me just take down your question here. So, and you could just hold there for a sec, Ben, in fact go back a slide. I feel like any operation, you have to be well planned ahead of time, and for the most part in planning ureteroscopy, that includes good imaging. Technically that's going to be a CT KUB, to find the anatomy, stone size, the parameters of the stone, also the inner density. So being well prepared, as you would with any operation.

Dr. John Denstedt:

And that would include a few practical things here. We are very fortunate here at our hospital to have, I'd say a semi dedicated staff. So nurses who are familiar with the operation, familiar with the equipment. And so forth. And that really smooths out the conduct, really, of the whole thing. And don't forget the x-ray technician, that's a critical part of things. So we always work with the CR for our ureteroscopic cases. We'll talk, I'm sure here, about radiation exposure, but we try to limit the fluro as much as we can. But an experienced x-ray technician is also critical to the smooth conduct of the case.

Dr. John Denstedt:

So good planning, familiarized staff, and if you go to the next slide, Ben, having the right equipment readily available in the operating room, which includes all the guide wires. In our standard wire, there've been some floppy tech wire, but you want to have hydrophilic guide wires available. Various catheters, dilators, including balloon dilators and so forth, in case you have to dilate. And I've mentioned the C arm.

Dr. John Denstedt:

So the basic technique is to get a good guide wire up. Usually we'll use a flexible cystoscope to pass the guide wire. And then we'll talk in more detail about safety wire versus no safety wire. But the first step is to put the wire up, and the flexible scope. And if you pause there, Ben, it goes up coaxially, then over the guide wire under fluoroscopic control, into the kidney.

Dr. John Denstedt:

And in a moment, we'll show all of that with the videos here. The OR set up is basically as you see in this slide in the way we have the screen, the C arm and so forth, in position. And at the foot of the patient, of course, our table with all of the various equipment.

Dr. Ben Chew:

I can echo that comment, when I left your place, it wasn't enough that I knew what was going on, but everybody else needs to know what's going on. And unlike you, I don't have Kathy running my C arm, and it requires quite a bit of coaching and making sure that you trust that other person and what to do.

Dr. John Denstedt:

Yeah. Well, it's often maybe not thought of until you end up in the position with unfamiliar staff and x-ray tech. And then you know, and I'm sure people on this call ... If you can just go back to the video there, Ben. I'll make a couple comments.

Dr. John Denstedt:

But yeah, familiarized staff is very important.

Dr. John Denstedt:

And we just see here, and if you pause there, Ben, having an adequate sized table at the foot of the patient with all your equipment, you see the setup there with our C arm, the anesthetist at the top. Of course these days, everybody's wearing one of these, and wearing one of these. I must say, the whole process, of course, has slowed down rather dramatically. Just from the COVID crisis. But, back in there, we produced this video pre-COVID, this is roughly the room setup. So if you scroll forward, Ben.

Dr. Ben Chew:

Question for you from Mexico. What about fluoro-less ureteroscopy?

Dr. John Denstedt:

Yes, so that's a great question, there's a lot of interest in that. This is the question about radiation exposure, we want to decrease that as much as we can. And certainly publish papers, and experienced developing fluoro-less. Personally, I still feel I'm working a little bit blind if I don't have the C arm. I think the vast majority of the case can be done with any fluoroscopy, but adequate positioning of the stent, if you've got a very impacted stone that you're trying to get a guide wire by, those situations, it's just, I have the full scope of what's going on if I have the C arm there. So our technique is to reduce the fluoro as much as we can, but we are not doing fluoro-less ureteroscopy at the present time. But, great question.

Dr. John Denstedt:

So we'll just let things play there, that's the basic setup, and we've got a flexible cystoscope, flexible ureteroscope, and we'll talk about the case here. So the first one is a 47 year old male. Morbidly obese, which applies to a lot of our patients. Presented with left flank pain and renal colic. And is parameters here for S wall are certainly not very good. Skin to stone distance, 14 centimeters, Hounsfield density is 1400, but for whatever reason, he had S wall failed. Not surprisingly, and if you pause there, Ben, so we elected to go ahead with the ureteroscopy.

Dr. John Denstedt:

And as I mentioned before, the first step, put up a guide wire. Now the use of a safety wire, I would typically work, if I had ureteral stone, I would always have a safety wire. As an alternative though, up in the kidney, if the stone is in the inter renal location, I usually do not work with a safety wire. So I just put one wire coaxially put the flexible ureteroscope up, and if you play the video, Ben, this will show the passage of the ureteroscope up over the guide wire.

Dr. John Denstedt:

What you're seeing there in the video, this fellow actually had a stent in, so we pulled the stent initially to the urethral meatus. You never want to give up anything, so we already had an access there, if you like, with the stent. Put the wire up through the stent, and we've now got a single wire curled up in the kidney. So then we'd always important to start out with the bladder empty. In this case, we're using a disposable flexible ureteroscope from one of the companies, and it's going up coaxially here, over the guide wire. This part we are going to follow in fluoro. And you'll see the scope advancing here over that guide wire. And we'd anticipate it would go up pretty easily because this person's had a stent in for likely at least a month. So the ureter is going to be pretty dilated.

Dr. John Denstedt:

So as you see, the scope goes up quite easily then, into the kidney. And the, the guide wire-

Dr. Ben Chew:

I have one more questions, Dr. Denstedt, from the audience. One of the, so in terms of guide wires, it's interesting, our poll says that 82% of people will use a safety wire. 9% sometimes, and 10% no. I guess it depends, but most people here are using a safety wire. And a couple questions about imaging. What do you do for your pre-op imaging? You showed us a CT scan there. Do you often get a CT scan? Or what's your routine for pre-op imaging?

Dr. John Denstedt:

Yeah. So most patients will end up with a CT. They have presented either through the ER or whatever. So we would typically be, by one means or another, most patients would have had a CT K&BCT with a contrast preoperatively. I think a combination of the K&B and an ultrasound is reasonable. That will give you enough anatomic detail and information about the stone. So, that's an alternative is a K&B and an ultrasound. Majority of our patients though, would at some point along the way, would've had the CT.

Dr. Ben Chew:

And this person had a stent beforehand. Do you routinely pre-stent your flexible ureteroscopy cases? And what do you feel about pre-stenting for flexible ureteroscopy?

Dr. John Denstedt:

So, another great question. Usually we do not. So, our practice is not to pre-stent the patient. The proponents of that, it could cause the passive dilation of the ureter, the scope will go up much easier and so forth. And there are certainly parts of the world, I know in China, for example, where I've operated on many occasions myself. In many of the Asian countries, actually, pre-stenting is part of the standard protocol. So patient gets the stent in, and taken back to the OR a week later for the ureteroscopy.

Dr. John Denstedt:

In our situation, obviously it's two operations, it might need two anesthetics, you've got a week of stent morbidity in between and so forth. So we try and do it as a single procedure without pre-stenting, is the short answer there.

Dr. Ben Chew:

Okay. Great, great. Thank you.

Dr. John Denstedt:

So, carrying on here, we've put the scope up, you can see from the view of that stone, it's pretty hard looking stone. Consistent with 1400 Hounsfield density. Probably a monohydrate stone. Patient had previously had an S wall sequence, that stone had been cracked into a few fragments, but obviously not broken down completely.

Dr. John Denstedt:

So, I think it was in the lower pull, we're using the laser. You see the parameter up there that we're using, .8 Jules, frequency of 12, to fragment those stones. And if you just pause there, Ben, on this slide.

Dr. John Denstedt:

Thank Olivier Traxer for this slide. The basic hand motions on the ureteroscope, especially for those who are kind of novices, or just starting to do this. So if you're right handed, the body of the scope is held in the right hand, and you've got the up and down deflection motions. Then as well, a rotational movement of the scope, all done with the right hand on the body of the scope, and then the third motion is the inner note, and that's done with the left hand down on the penis, or at the urethra meatus to move the scope in and out. So those basic hand positions are critically important, as a part of routine flexible ureteroscopy.

Dr. Ben Chew:

Questions about ureteral access sheath. They notice you're not using a sheath in this case, when do you use a sheath?

Dr. John Denstedt:

Yeah, so as I recall coming up here, not using a sheath yet in this case, but you'll see, I think we do ultimately put one in. But the basic question I have made sparing use, I think, compared to others, of access sheaths, and we're starting to see it come into play here. I never use a ureteral access sheath on the ureter, for ureteral stones. Where I do use it is for intra renal stones, particularly larger stones, where you might be anticipating multiple passages of the ureteroscope up and down. That's obviously greatly facilitated by use of a access sheath.

Dr. John Denstedt:

But at least, on our hands, overall use of sheaths is perhaps 10 to 15% of all of our cases, which is probably less than I suspect others. In fact there are surveys that are published on use of access sheaths. And we tend to use them a little more sparingly. So, what we're seeing here now is passage of a access sheath. What I use is a 12/14 access sheath. And those come in different lengths, of course. We would use a short one in a female patient, a longer, perhaps 45 centimeter sheath in a male patient. And then we're passing this up over a guide wire.

Dr. John Denstedt:

So I think you can go ahead and play the video there, Ben.

Dr. Ben Chew:

And do you perform a retrograde pyelogram before inserting the sheath?

Dr. John Denstedt:

Not as a routine. I think the most critical thing about passing sheaths is not to force it. It has to go smoothly and easily. We've all seen the pictures from Olivia and his publication on ureteral injuries with access sheaths. I've certainly seen my share of those myself. They're more common with patients who have not had a stent in, for example. And we've actually seen avulsions from access sheaths. A whole ureter extracted by an access sheath. So, I think the main point is you want to be very careful, and we'll see it here in a moment, that it's going smoothly and easily as you place up the access sheath.

Dr. John Denstedt:

So, obviously it's going in over the guide wire, in this case as well. We're going to follow, you'll see on fluoroscopy here, with C arm. So you'll gradually see here, here's the passage of the sheath with a gentle pressure on advancing it up. And then typically we're going to, for inter renal stone, we'll drop it just below the UPJ. The upper end of that is where we would leave that. You're going to take the stylet out of the access sheath, and remove the safety wire as well. And then we have the sheath in place there.

Dr. John Denstedt:

So, and you can pause on this slide, Ben. We've talked a bit already about the use of safety wires. We've had a good question there from the audience, so there's numerous publications that have looked at this. It was dogma in the past, you always have a safety wire as a routine with any ureteroscopy. I've provided our general approach, I do have a safety wire, pretty much as a routine for ureteral stone, and for an inter renal stone, where you're not going to lose lumen, or you've got a wider field of view. And I find the guide wire gets in place, it gets in the way, if you like. It's curled up in the kidney, you don't want to laser the guide wire, so I take it out when I'm working up in the kidney. And that's my general approach.

Dr. Ben Chew:

Gotcha. And other people are sort of saying, do you stent after you put in an access sheath? And why not use a 10/12 rather than a 12/14?

Dr. John Denstedt:

Yes, so the stenting question, I think we'll address that in a little bit more detail later. But specific to that exact question, if I use an access sheath, then yes, I would stent all of those patients. We'll talk, again, in more detail about when to stent versus not stent. But if I have used an access sheath, I would put up a stent routinely after that.

Dr. John Denstedt:

And the other question is the size of the access sheath, I described a 12/14. Obviously that's a little bit larger, perhaps you're going to get a little more flow through that. Advantages overall of access sheaths might include better visibility, better irrigation, flow, perhaps decreased rates of sepsis. And we'll talk a bit more about sepsis here in a minute. Because of decreased pressure up in the kidney while you're working. I think there's much more attention being paid now to inter renal pressures with ureteroscopy. And rates of sepsis and so forth. So those are the advantages of access sheath.

Dr. Ben Chew:

Where do you like to park the access sheath when you actually put it in? Do you try to get it right into the renal pelvis? Or below? Does that matter on how it impacts the renal pressure?

Dr. John Denstedt:

Yeah, I mean I generally have been ... Tend to drop it just below the UPJ. So not all the way up into the renal pelvis. If it's right in the renal pelvis, you can kind of get stuck on it, and hooked as you're trying to manipulate the ureteroscope. So, it's primarily for that reason, so I can take full advantage of all of the flexion of the ureteroscope. I would drop it, typically just below the UPJ.

Dr. Ben Chew:

Okay, and in terms of teaching how to use someone, or teaching a resident on how much force they can use to insert the ureteral access sheath, do you have any tips?

Dr. John Denstedt:

Yes, so for us that's more, I would say experience and judgment. And just being careful. And anything that's taking a lot of pressure, whether it's an an access sheath or a scope, or whatever it is, not good. That's where you're going to risk ureteral injury and perforation and so forth. So, it's just like any other surgical principle. You want to be gentle with the approach, and with an access sheath, you want to feel that it is not binding on the ureter, that it is smoothly going up into the ureter, and as I mentioned, we follow that with fluoro.

Dr. Ben Chew:

Yeah, gotcha. The one thing I learned from someone too, is that you can't really tell how much pressure someone's putting on it. So what you can do is basically put your hand on top of the resident's hand to sort of get a feel of how much pressure he or she is putting on. Or they can also put their hand on top of yours so that you can show them how much pressure you're actually applying.

Dr. John Denstedt:

Yeah. That's a great tip, Ben. Particularly with the more junior residents perhaps. Obviously where there's less experience, that's a great trick.

Dr. Ben Chew:

Great. Well, continue on the video.

Dr. John Denstedt:

So here, and again, we're using in this case, a disposable ureteroscope, and I'm sure we'll talk here about pros, cons of disposable versus reusable scopes. This happened to be one of the disposables. Now when do I use? I do not use disposable scopes routinely in all of our cases. In fact, the bulk of our cases are still done with reusable digital flexible ureteroscopes. I do tend to use the disposable equipment when it's a tough case. What do I mean by that? A tough case, a lower pulse stone, where you're really going to have to crank perhaps, on the instrument to get down into the lower pulse. This stone happens to be in the lower pulse. So those types of cases are where I would selectively use disposable instrumentation.

Dr. John Denstedt:

And here, we're extracting fragments. We've already fragmented with the Holmium laser. And you have to be very careful with this piece. Always see that the stone is coming smoothly down the ureter, not getting caught or binding. And here, we're pulling the stone back into the access sheath, and it can get hung up in the tip of the sheath. You have to be careful with that.

Dr. John Denstedt:

But then, once you're in the sheath, usually it will come out quite easily. We're using a 1.5 french [inaudible 00:30:42] basket there, to extract these fragments.

Dr. Ben Chew:

What kind of irrigation are you using? Is it pressurized irrigation?

Dr. John Denstedt:

So, a great question. So typically I would start out with a gravity irrigation, just a bag of saline solution on gravity. But more often than not, we will go to pressurized irrigation. And there's different devices out there, and specially designed syringes, and foot pounds. I tend to use just a couple of syringes, actually two 50 cc syringes with an IV extension tubing. It's very inexpensive, and use the pressurized irrigation in that fashion.

Dr. John Denstedt:

So, if I've got a good visibility with gravity, I'll just go with ... And the whole thing there is about visibility. You have to be able to see what you're doing. And if you can't see, then that's when I would switch over to pressurized irrigation.

Dr. Ben Chew:

Here's a great question, how do you handle basketing in a sheathless approach, if you have no access sheath up?

Dr. John Denstedt:

Yeah. So our general approach to most stones, certainly in the ureter, is not actually to do a lot of basketing. So it's a fragmentation procedure. Fragment the stone, leave the stent, and allow the patients to pass the fragments afterwards. And that's been my general approach for most or all of my career. So the answer to the question is, I'm usually not basketing stones without an access sheath. So, I'm not pulling things down through the ureter. I'll only do that with an access sheath.

Dr. Ben Chew:

Gotcha. And another good question is, what are your tips to figure out, when you're looking at a stone, it's actually small enough to fit through your sheath?

Dr. John Denstedt:

Yeah, that is a great question. And it's trickier than you might think. The common thing is, it looks like it should easily be extractable back into the sheath, but my experience is, the stones have to actually be smaller than you think. That they tend to be a little larger than you think, and then get hung up on the tip of the sheath. So you want to be sure the stone is pretty well fragmented, which we do anyway, because the other risk there is getting a stone stuck in a basket. And we can talk about that situation and how to handle it.

Dr. John Denstedt:

So you always want to be sure that the stone is of a size that will easily fall out of the basket, if you have to fragment it further. And small enough that it's going to fit back into the sheath.

Dr. Ben Chew:

So right here, it got hung up just for a tiny bit, right at the end of the access sheath. What's going through your mind here? And what little things are you doing to try to get it through?

Dr. John Denstedt:

Yes, so you can rotate it a little bit. It may just be hung up the way it's oriented at the tip of the sheath. Again, it's a gentle approach to have it work its way into the sheath. But the main thing here is to avoid injury and complications. And if it's hung up, and it's not going to come back into the sheath, then push it back up into the kidney, drop it, and it's going to need to be fragmented further.

Dr. Ben Chew:

Right. How do you determine what laser settings you're going to use when you're fragmenting the stone here?

Dr. John Denstedt:

Yeah, so we'll talk in more detail as we go along here. But, fragmentation versus dusting and so forth. I would ... a general approach that I use is if it's a softer stone, either from the CT, or just visually, it can often tell, I might be more inclined to use a dusting approach, in a very soft stone. It's going to fragment easily ... or not fragment, but dust into the small crystals, if you like. An extremely hard stone, often you're going to end up fragmenting anyway, to break down a very hard stone.

Dr. John Denstedt:

So hard stones, I would fragment, the very soft stones, I'd be more inclined to use a dusting approach.

Dr. Ben Chew:

Gotcha, gotcha. Great. Okay.

Dr. John Denstedt:

So, what we're seeing here in this, in fact one point you can see I inject contrast up. So that's dilute contrast, and that gives you a roadmap of the kidney. It's often hard to tell which calyx you're in, certainly when you're starting with ureteroscopy. If you pause the video, Ben. Because all the calyxes endoscopically kind of look the same. Upper pole, lower pole. With experience from the orientation of your hands, you can often tell in the upper pole or lower pole, but putting a little contrast in the kidney really gives you the roadmap there, you can follow with just very limited fluoro. Then, check all of the calyxes in a systematic way. I'm in the upper pole, mid calyx, and then lower pole, and make sure you've examined the whole kidney. So that's what that was about.

Dr. John Denstedt:

Then if you play the video again, Ben, at the conclusion here, we're going to place the stent. So, we put a guide wire back up into the kidney, and we're going to stent here through the existing ureteral access sheath that we used. All of our stents are put in entirely using a fluoroscopic approach, not looking into the bladder with the scope. We've got a metal tipped pusher here, that can be seen on fluro to advance that stent over the guide wire. And then we'll see in a moment here, the fluoroscopic image. Obviously you want the stent well curled up in the kidney. The critical part of this whole thing, because you're not looking in the bladder with the scope, is to not shove the stent up in the ureter. Which can be surprisingly difficult to sort that out, if you get it misplaced up in the ureter.

Dr. John Denstedt:

So we look on fluoro, and you see a fluoroscopic image, you see the metal tipped pusher there. A rough guideline is a female patients would be the lower border of the synthesis, or perhaps mid synthesis. Males you can go up even to the upper border. And then pull the wire, and the stent will curl. Now here, you can see we've dropped it off, actually in the urethra, which was better than having it up in the ureter. And if that's the case, as soon as you pass the catheter at the conclusion of the case, now we'll flip the stent up into the bladder and you can see it's curled up well there in the bladder.

Dr. John Denstedt:

So maybe pause there, Ben.

Dr. Ben Chew:

Yeah.

Dr. John Denstedt:

And we'll take some questions.

Dr. Ben Chew:

We've got a lot of questions here. One question I have is, you were stenting through the ureteral access sheath, and one of the recommendations is to evaluate the ureter afterwards when you're coming out to see if there's any splits or perforations, just to help you determine how long to leave your stent in. Do you always stent through the access sheath? And when do you inspect the ureter.

Dr. John Denstedt:

Okay. So as I described earlier, we are using access sheaths sparingly. So for me, this is partly for the demonstration to show a use of the access sheath. So, the approach though, if there is no access sheath, then it is good to examine the ureter, it's described on the way out, endoscopically to be sure there's no ureteral entries and so forth.

Dr. John Denstedt:

Here, obviously, we haven't examined the ureter, but I'm probably confident enough, and the patient had been stented, access sheath went up quite easily, so forth, that things are fine. But I think that whoever asked that question, it's a good point about ureteral examination for injury to help define how long to leave the stent in.

Dr. Ben Chew:

Yeah. Right, right, right. Okay. And then, what's your personal rate of stricture, would you find with the use of access sheaths?

Dr. John Denstedt:

Yeah, so stricture rates have come down, over the years, for everybody. And that's a result of the improved instrumentation. The stricture rate in the early days, ureteroscopy was as high as three to five percent, even higher. Because of a lot of balloon dilation of the ureter, the large instrumentation was more ureteral injuries. And in the modern era, strictures are down 1% or even less now. So the stricture rate on day to day practice should be extremely low, I would say.

Dr. John Denstedt:

And in our own practices, in fact, extremely low. We'll maybe talk here about routine imaging, post ureteroscopy, when to do that and so forth, but overall it was a well conducted procedure, with small instrumentation, no ureteral injury, stricture rate should be easily less than 1%.

Dr. Ben Chew:

Great question from Thailand here. Do you have, for large stones, do you have a time limit for ureteroscopy?

Dr. John Denstedt:

Yes. So, as I had mentioned at the outset here, I generally will limit the amount of time I'm working to 90 minutes. And most cases will take considerably less than that. But, for a larger stone that we see an anti coagulated patient, we're taking on a two and a half centimeter stone, I would generally tend to limit our time to 90 minutes. And that's just if you're using pressurized irrigation, forneseal rupture, and if you end up working two, three hours or something like that, I think the overall complication rates, specifically sepsis, are actually higher. So I would rather stage an operation if it's going to take three hours, divide it into two procedures, than work for two to three hours.

Dr. Ben Chew:

Gotcha. And then in terms of stenting, you were one of the first ones to do a prospective stent versus no stent trial and publish that for ureteroscopy. A very highly set up application. But one other question is, if you're not using a ureteral access sheath, and you're just dusting, does that change your indication for leaving a stent at the end of the case?

Dr. John Denstedt:

Yes. So, dogma years ago, in effect it's still pretty common practice for a lot of people, is to routinely leave a stent after all ureteroscopic cases. And that's a reasonable approach is to stent everybody. Of course you will then commit that 100% of people to the morbidity, pain, dysuria, all of the well-known stent symptoms. So, the reason we did that initial trial, it's been replicated by others many times, is to try and get away from routine stenting in suitable patients.

Dr. John Denstedt:

So, a rough guideline practically, for people here, is good indications to stent are use of a sheath, if you balloon dilated the ureter, if it's a very impacted stone, if there's one kidney, if you've done a bilateral case, you're going to want to stent at least one side. A lot of this is common sense and logical. But, when not to stent, that type of case would be somebody who'd been pre-stented for example. They've got a dilated ureter. Smaller stone, not impacted, where you have ... And a lot of this is judgment, actually. So that you feel most likely that this patient is going to be okay without committing them to a ureteral stent to pass the fragments and so forth. So, if there's overall less manipulation of the ureter, those are the patients you might consider not stenting.

Dr. John Denstedt:

And recognizing there will be a small rate where even you've made, you think the right judgment, that they will have colic and problems afterwards, and have to return to the OR. But I think if you're picking the right cases, the chance of that should be very low. And finally, any ureteral injury, from the laser, from whatever. Those patients should all have a stent put in afterwards.

Dr. Ben Chew:

All right, should we go onto the next case, Dr. Denstedt?

Dr. John Denstedt:

Sure.

Dr. Ben Chew:

Great.

Dr. John Denstedt:

And as we're waiting for that, I'll just add, we usually would leave the stent for about a week after the case is over, unless there's been a ureteral injury, we might leave it two to four weeks, with four being probably the maximum. But most stents are typically left in for one week afterwards.

Dr. Ben Chew:

And you remove most of those cystoscopically?

Dr. John Denstedt:

Correct. So the debate there is leave the strings on, and remove it in that fashion. Our general practice is to take the strings off, and we'll remove the stent with a flexible cystoscope in the clinic later on.

Dr. John Denstedt:

So the next case here, 70 year old woman, right renal colic. We've got a 12 millimeter stone in the right renal pelvis. Again, a hard stone. That's with hard stone, that's with unit density of 1500, so unlikely to fragment with shockwave. And this is a patient where I would discuss the options shockwave versus ureteroscopy. Here we've elected to go ahead with ureteroscopy.

Dr. John Denstedt:

And same approach as in the prior case. We put a wire up. We've not used a safety wire. And then we're going to coaxially here, same as the previous case, put the scope up over the guide wire, and then we'll follow this on fluoro. And here we are, we're getting hung up at the ureteral orifice. And if you pause the video, Ben, the first maneuver, if you have this situation, is to turn the scope, actually rotate it. Because most working channels are offset a little bit in the scope. And you could be getting caught on the lip, if you like, of the ureteral orifice. So if you just rotate it, there's a percentage of cases then, where the scope will actually follow the wire, and you won't have to dilate.

Dr. John Denstedt:

If you play the video again, Ben. You can see, so we did that, we rotated the scope, we've tried to pass it, and it still wouldn't go. So the next step is a 8/10 coaxial dilator. They're cheaper than balloon dilators, and only dilates to 10 French. So we passed that over the wire, and then I believe you'll see here, so that didn't work as well. Didn't give us enough dilation, so now I'm going to balloon dilator.

Dr. John Denstedt:

My experience with this is a more common thing that you might think. In an un-stented patient. Here, very high rates, if you pause the video, Ben, of scopes going up without any difficulty at all. If I had to guess it's maybe one in every 15 cases, perhaps. That I've done and have to go to dilating. And I don't hesitate to dilate if I have to. It was the routine in all ureteroscopies for many, many years. So I'm not hesitant if I have to do this.

Dr. John Denstedt:

So, you can see the waist on the balloon, that's a six millimeter balloon dilating to 18 Rrench. It's 10 centimeters in length. I like a longer balloon. Most of it here is in the urethra. You just put enough up there so you're catching the orifice, and then you inflate that with contrast. If you play the video, Ben, under fluoroscopic view. And you will see the balloon will open here, and now you've got a satisfactory dilation of that orifice.

Dr. John Denstedt:

I still would not put a safety wire here. I don't think this stone is up in the kidney. So we'll remove the balloon dilator, and then coaxially put the flexible ureteroscope up, again, without the safety wire.

Dr. Ben Chew:

Does this change your decision on whether you're going to leave a stent or not? If you balloon dilate the ureteral orifice?

Dr. John Denstedt:

It certainly does. So all of these patients, I would stent. I think there is going to be enough ureteral edema and so forth. You've opened up that orifice and it may not drain properly afterwards, so I would stent all of those patients that I had dilated.

Dr. Ben Chew:

Also been a lot of questions, besides doing this, what about using optical dilation or going in with a semi rigid ureteroscope?

Dr. John Denstedt:

Yes. I don't use that particular technique myself, but I've certainly have seen it in many occasions, and there are people where it's a routine part of practice, actually. And I think that's another way of achieving the same thing. So, if you look up with a rigid scope, it's under vision, it's well controlled, that will give you enough dilation and accomplish similar to what you saw there with the balloon dilator. So I think it's a very reasonable approach to take.

Dr. John Denstedt:

So here, and in this case, we're using, again, a disposable scope. Now in this case you'll see a ball tip laser fiber. And actually if you're using a disposable ureteroscope, there's probably not much rationale actually to a ball tip fiber. I think the main place for ball tip fibers is in digital, reusable equipment. And the theory being that it's less likely to injure the working channel of the ureteroscope. Particularly if you've got a lot of deflection of the scope. You can advance no ball tip laser fiber and puncture the working channel. So if you are anticipating a lot of deflection in a reusable digital ureteroscope, that's where ball tip fibers might be useful.

Dr. John Denstedt:

You could pause for a minute, Ben. I don't know what you've found, but my experience with the ball tips are less efficient than a non-ball tip laser fiber. I haven't studied that critically, but perhaps it's our technique of fragmentation and plugging holes with a non-ball tip laser fiber. But to me, my general approach these seem to be a bit less efficient. They'll do the job, but less efficient.

Dr. Ben Chew:

I don't have much experience with ball tip fibers, actually. We reuse our fibers here. So we're not using the ball tip ones. I'm sure Bodo Knudsen, who's a fiber expert would probably have something to say about that.

Dr. Ben Chew:

Question for you about laser goggles, do you routinely wear laser goggles during laser lithotripsy?

Dr. John Denstedt:

So honestly, I do not. And we've just published a paper recently actually, Jim Waterson in Ottawa, it was a survey across Canada, which people could look up, and it's surprisingly how many people don't use the goggles. I mean, if you look, the textbook answer to this, obviously for safety and compliance and laser, and so forth is to wear the goggles. The laser physics of holmium are such that in error, at the usual parameters that we're using in holmium, it's going a centimeter bollister, a few millimeters, you'd actually have to stick it in your eye, fire it to have an injury. So most of the time, you're working well away from the margin of safety here is very large.

Dr. John Denstedt:

So personally, I have not been using laser glasses as a routine.

Dr. Ben Chew:

Okay. And what's your thought about lasers? High versus low power? A holmium:YAG versus a thulium fiber?

Dr. John Denstedt:

Yes, so I do not have a filum laser. I actually have used it, interestingly enough, in India. Where I was operating last year, with Ravindra Sabnison, and some other cases in India, and I was impressed, I have to say. So, I wish I had it actually, myself. And it looks like a very interesting tool. What was I impressed with? It was the efficiency and the rapidity of the small fragmentation. I mean I believe the rates on that laser go up to 2000 hertz. It just did a couple of cases, but was immediately impressed with the efficiency of that.

Dr. John Denstedt:

So our standard lithotriptor here in [inaudible 00:51:50] is still holmium.

Dr. Ben Chew:

And do you think that you need a high power laser?

Dr. John Denstedt:

Most human kidney stones will fragment with 10 watts of power. And an extremely hard stone, might take longer. I think we Sistine stone here, Sistine for example, might ... You'd take advantage of the higher power. The very initial holmium lasers on the market were only 10 or 20 watts maximum. We worked with that for many, many years. So, it is nice to have the availability of the higher power laser, I would say that. In particularly actually for bladder stones. I use holmium on bladder stones, and I think we're seeing more bladder stones now, just an impression.

Dr. John Denstedt:

But, larger bladder stones, that's really where I take a lot of advantage of the higher powered laser.

Dr. Ben Chew:

Should we continue on?

Dr. John Denstedt:

Sure.

Dr. John Denstedt:

So, here, and I think this is a stone that actually endoscopically looks a little bit softer than what was quoted there. The 1400 Hounsfield unit density. In any case, we would've fragmented it, there's the various techniques. You may want to pause here, Ben. This was an excellent study by yourself and others, comparing stone free rates with dusting and fragmentation. And I want to get it correct here, and not misquote you or anything. But, I think the bottom line was both will work?

Dr. John Denstedt:

Why don't you pick up on that.

Dr. Ben Chew:

I mean, on uni-varied analysis on six weeks, it did show that the stone free was higher with basketing, but then a multi varied analysis, it actually didn't pan out. So did we not have enough patients? But basically what we're saying though ... Or is six weeks to early? But what we're saying though is really dusting versus basketing, were equivalent statistically.

Dr. Ben Chew:

So really, we're actually just following those patients up to see what happened to them after a year's time. And we're just looking at that data now. But right now we show that there's no difference between dusting versus fragmenting.

Dr. John Denstedt:

Okay, great. So we should scroll forward here. Or play.

Dr. Ben Chew:

And like you said, I think people are asking can you dust with a low power laser. And I think absolutely you can. I think you would agree?

Dr. John Denstedt:

Yes. Yep.

Dr. Ben Chew:

Okay.

Dr. John Denstedt:

So the goal here in this case, which was done all without an access sheath, as I think you can see, was fragmentation. Then stenting at the conclusion of the case. I think you'd agree that stone looks a little softer now. Our visibility there, we're using a disposable scope. And it's not quite as sharp of visibility, as you would see with our capital equipment.

Dr. John Denstedt:

We would use, happens to be Olympus at our institution. Integrated OR's it's digital ureteroscopes. And the visibility would be better with that kind of instrumentation. Here, it's not as crisp and sharp as with the capital equipment.

Dr. Ben Chew:

What about laser with Moses technology? Do you have any experience with that? And your thoughts about that?

Dr. John Denstedt:

So again, I'm not using that myself. I'm following it with great interest. Modi Dafdivani and others, he being in Israel, have done a lot of investigative work. And of course [inaudible 00:55:39] and Mustaf Al Hallali before he passed, over in Montreal. And I'm impressed, just following in the literature, that perhaps it seems to be more efficient. And so forth, I think we need further studies and time will tell.

Dr. John Denstedt:

But the Moses, are you using it, Ben? Moses?

Dr. Ben Chew:

We do not have Moses either. We do have the filum fiber laser though. And like you said, it is very efficient and I'm just noticing your technique here. In terms of the pop dusting, basically, I found that with holmium you need to be a bit directed, and the stone moves around quite a bit. With the thulium fiber, I find the stone stays quite stable, and it does fragment very well because of the way the energy is delivered. It's a slightly different wavelength as well too. So, when I have junior residents working, who aren't as adept at showing all those traction movements you were showing with painting it up and down like you've taught me. You basically can just put the fiber into the calyx and just step on the pedal. And a few minutes later, the stone is gone. It's really quite amazing.

Dr. Ben Chew:

But this brings us to a good question someone was asking us, actually. This is always an age old question. What size of the fragments do you consider dust? When do you know how to stop here and say, "These are going to pass?"

Dr. John Denstedt:

Yes. That is a great question. So there are a few reference points that you would have available to you. If you did have a guide where your safety wire, you can compare the wire with the fragments. You've got the tip of the laser here as a reference point for you. Again, I think a lot of that though is judgment and experience. And I try and get the stone fragments, obviously around one to two millimeters in size, so they're readily passable. But let me say, you don't want to get them too small.

Dr. John Denstedt:

If you are chasing after crystals, the chance of urethral injury or plugging a hole on a calyx with the laser, if you're after very small fragments. The benefit of that, the pros and cons weigh the scales towards don't try and make it into very small crystals. But as a guideline, one or two millimeter stone fragments are usually going to pass quite easily.

Dr. John Denstedt:

And then, I think here at the end, Ben, we're just going to stent. What you may want to do, and it's the same technique, I think we showed earlier. Using fluoroscopy. If you scroll forward a little bit to the next case, in the interest of time. There it was. So, either one is fine. So this, if it was the last case.

Dr. Ben Chew:

This is the last case. Did you want to see ... Sorry, there was another case before this section. Did you want to see case three?

Dr. John Denstedt:

You could put up the prior case, Ben.

Dr. Ben Chew:

Sure.

Dr. John Denstedt:

Case three. So this case I believe a 55 year old man. Right flank pain, renal pelvic stone, as shown here. And again, this patient we discussed as well, versus ureteroscopy, elected to go ahead. So same procedure, we're passing up a guide wire with a flexible scope here. Under fluoroscopic control The ureteroscope would be passed up, again, coaxially. We would not use a safety wire. Same basic technique as shown earlier. I think in this case, we did not have to dilate, as I recall. Yeah, there goes the scope, it's going up easily into the kidney. And then similar general approach to stone fragmentation. One point here, the lower pole can be the tricky part of this. If the stones drop into the lower pole, or if they originated in the lower pole, and this might've been the case where we perhaps demonstrated use of a stone basket to reposition stones.

Dr. John Denstedt:

So if it's in the lower pole, use a 1.5 French [inaudible 00:59:56] basket, you can reposition them up into a more advantageous location. And the, I think Ben, you can probably scroll forward to the last case here. Which, happened to be a Sistine stone. And patient clearly, that's not going to work with this. There's the CT images, the stone is for the most part in the lower pole of the kidney. It's a reasonably good sized stone. Probably a centimeter and a half or so. And in an awkward place down in the lower pole.

Dr. John Denstedt:

So this kind of case, I think is a good one for a disposable ureteroscope, where you can expect you're going to have to crank quite a bit down into that lower pole.

Dr. Ben Chew:

And you've always taught me to use the lower pole stones into the upper pole. That's presuming of course, you can move it. This stone looks way too big to move. So what are your principles here?

Dr. John Denstedt:

Yes, so my principles with that, if you can get at it, and see it, and get the laser fiber on it, I would not reposition it. And so that's how I do that. If I can see it, then I'll fragment it in site, if you like, in the lower pole. So here, we're putting contrast to give us the roadmap of that collecting system, I think you can see. It's a bit of a bifid collecting system. You'll see the stone there is filling defect. And in kind of an awkward angle. So, again, if I can see it, I'll fragment it in site. If I can't get the laser fiber quite applied to it, that's when I would basket it and relocate it.

Dr. Ben Chew:

I think we've still got, we can go on for another 10 minutes or so. I think that'd be fine. What percent of the cases do you use a fiber optic flexible ureteroscope? And it is important still to have those around?

Dr. John Denstedt:

Yes. So I would say the majority, actually, of our cases are still done with reusable capital equipment ureteroscopes, and they're all digital.

Dr. Ben Chew:

Do you use any fiber optic scopes?

Dr. John Denstedt:

No.

Dr. Ben Chew:

No?

Dr. John Denstedt:

Not now for ureteroscopies. So, in this case, actually this stone turned out to be, rather than one large stone, it was actually several smaller stones. They were just packed on that calyx. And I think this was a case where I actually did do a little bit of repositioning actually of that stone. So pull it out of the lower pole, put it in a more advantageous location, which quite often the upper pole fills that criteria. It's easy to get into the upper pole. And the, at the conclusion here, we then stented the patient. I think we did do basketing here, it's a Sistine stone form. So you really want to work to have the fragments removed there. So we would do stone basketing there as well. Through the access sheath.

Dr. Ben Chew:

Great question from Mexico. In cases such as this, where it's pretty big, and really you could to a PC&L, but obviously because she's a Sistine uric, you decided to do this. Do you ever consent patients and position them differently in order that you may do a PC&L at the same time of the ureteroscopy?

Dr. John Denstedt:

So, no. It's usually one or the other. We're either doing a PC&L or we're doing a ureteroscopy. And for us, the ureteroscopy is always in the lithotomy position. And for us, if I'm doing a PC&L, I still do all of my perks in a prone position. I'm not doing supine PC&L. So they would all be positioned, and we start out actually, with the patient in the prone position. Not in lithotomy. Use the flexible scope to put a wire and a catheter up, inject contrast, and then put the perk in. So that's how I would approach it.

Dr. Ben Chew:

I'm getting a lot of questions here about what your laser settings are for dusting versus fragmenting.

Dr. John Denstedt:

Okay. Well, the general principle here. The dusting is at a lower power. So, .4, perhaps .6 Jules at a higher rate. Which would be 20 hertz or 40 hertz. So, initially, most cases I start at .8 Jules at a rate of 10 and then alter things from there. And that could include going up to 20 or 40 hertz on the laser. So a very rapid rate. Fragmenting is generally kind of the opposite of that. So higher power, lower rate. And in extremely hard stones, I might go up to two Jules, two and a half Jules of energy. With a low rate to achieve fragmentation of a very hard stone. That's rough principles concerning.

Dr. Ben Chew:

And during this COVID time now, are you doing any changes in anesthesia? For instance, are you doing more spinal anesthetics?

Dr. John Denstedt:

Yeah. What a great and timely question. So, I actually operated ... Today's Friday, two days ago. We did three cases, almost the only three I've done in the last month. And I must, and I'm sure everyone is experiencing this, the patient is intubated, I did them under general. Everybody's out of the room for 15 minutes, waiting after the intubation. And then at the conclusion of the case, the same thing. After the patients, another 15 minutes. It's a dramatically slowed down the processing of patients through the operating. It takes about twice as long. The surgical time is the same, but the overall conduct of the case.

Dr. John Denstedt:

And I've certainly been hearing people doing ... We do all ours under general anesthetic, just general ureteroscopy. I hear of a migration to spinal anesthesia, which I think could work very well, to avoid the whole scenario of intubation, air exchanges in the room, and so forth. So that might be a reasonable approach. Particularly if the spinal was done beforehand in a block room, for example. And the patient, if you had two side by side ORs with two teams. You could perhaps gain back some of that efficiency that's been lost here during the COVID time.

Dr. Ben Chew:

And just to end off the other parts, what did you do for your post-operative imaging?

Dr. John Denstedt:

Yes, so the usual post op protocol if they're stented, we see them the next week, pull the stent. And then the classic question is, does every patient after ureteroscopy need ultrasound, effectively to rule out a silent ureteral stricture? And of course, this is in our guidelines, AUA, EAU I believe as well. And that had been dogma, that every patient, to rule out a silent stricture. I must say, myself, I tend to individualize the patients. So a patient with a small ureteral stone was opaque, you can see in a KUB x-ray, was completely fragmented, pull the stent, patient's fine, no pain. Urine culture negative. KUB looks clear, no stone. In that particular patient, I would likely not be routinely getting a renal ultrasound to rule out a stricture.

Dr. John Denstedt:

If I knew the case went well and so forth. Majority of patients, yes, we'd probably still have a routine ultrasound. Perhaps combined with a KUB. We would not routinely CT, just from radiation point of view, exposure. But I think there are patients who, and it's cost saving and so forth, where we would not do a routine ultrasound.

Dr. Ben Chew:

Great. Thank you very much for all those insights, Dr. Denstedt and all those cases. I think we saw some great demonstrations on how to get access, I think that's one of the most important things. Don't be afraid to balloon dilate the ureter if you have to. It's not very common. The less expensive option is the 8/10 dilator. Stenting most of the cases, ureteral access sheath just when you need to. And not always necessary to get a safety wire. But, certainly decide whether you're going to fragment or dust the stone into pieces. And post-operative imaging, which is part of most guidelines, is probably really a must do.

Dr. Ben Chew:

I don't know if you want to close with any other words, Dr. Denstedt about ureteroscopy.

Dr. John Denstedt:

I think that's a great summary there, Ben, of the points. And I hope people found this to be useful. I enjoyed doing it, and greatly appreciate the opportunity here, to interact with people. The questions were fantastic.

Dr. Ben Chew:

But yeah, thank you to the hundreds of people that have attended this that are in the room right now. I'm sorry we couldn't get to all your questions. It's literally just kind of coming down, and I'm just kind of drinking from a fire hose here trying to ask Dr. Denstedt all these questions. So, thank you very much. Please, when you do leave the seminar, it will take you to a survey in order to get your CE credits. Please fill out the post webinar survey, and then as mentioned, Michelle Paoli, because we have your email when you registered, will be sending you something at the end of the month, that you'll click on and then you'll get your CME certificate.

Dr. Ben Chew:

And please sign up for next week, when Dr. Brian Eisner will be moderating Dr. Guido Giusti using ureteroscopy using a high power [inaudible 01:10:01] laser. And the registration can be found on our website, endourology.org under the education link, and then master class in endourology. So please go ahead and register for that. And thank you again, Dr. Denstedt and thank you to the Endo Society.

Dr. Ben Chew:

Have a good day.

Dr. John Denstedt:

Thank you, Ben. And I look forward to seeing everybody in person once we get through these difficult times here.

Dr. Ben Chew:

Everyone stay safe. Thank you.

Dr. John Denstedt:

Okay, thank you. Goodnight.