of the Pacific Northwest Center. And he's been an innovator over a very long period of time. He has many patents. He was the inventor of the hot axios, a lumen opposing stent, which was a fantastic innovation. And his expertise spans a full gamut of endoscopy from ERCP to EUS, to Barrett's to Colin, every aspect of endoscopy. So welcome Ken, and thank you for joining us. First of all, I'd like to thank Jason and Robert and the ASGE for this opportunity to present at this inaugural virtual ASGE postgraduate course. My disclosure, so let's start with terminology. You've probably seen the term water immersion and water exchange. They are very different. Now both use water infusion by a water pump during insertion of the colonoscope to the cecum. But with water immersion, we leave the gas on. You can insufflate gas, ideally it should be CO2 as an option, if you think it will help you get to the cecum. You infuse the water to assist progression to the cecum. So this is using water as an aid really to conventional colonoscopy. Water exchange is different. Here we turn the gas off. And we are only infusing water. We want to aspirate all gas pockets. We want to get all the bubbles out, any residual pockets. And we want to also aspirate any contaminated contents. We will infuse water to maintain a clear view of the lumen. So when I use water exchange, my foot is on the water pump pedal pretty much the entire time. And I'm constantly aspirating contents. So I keep the lumen just distended enough so that I can see. But I'm doing a recycling of the old dirty water for the new clean water. Those of us who have been scuba diving or snorkeling know the advantages of underwater imaging. You get these magnificent views underwater. A lot of it is the magnification effect. It's 1.33 fold. But also the images are crisp, clear, and so color intense, as you can see here. I call water the do-it-yourself magnifying glass. It's a poor man's magnifying glass. There's no light reflection artifact. And that can cause a lot of confusion when you're using gas and impede your visualization of fine detail. There's no fogging. And you get this 3D floating effect. And this is really, I think, the key advantage of underwater. And that led me to using it for underwater EMR. So here you see an example with gas. You get this light reflection artifact here. And underwater, it's gone. And so you can see the fine detail. This is a SSA here. You can see the fine detail. Video capsule endoscopy is an underwater imaging procedure. That explains why we have, despite a very primitive CMOS chip, these beautiful images showing the villi standing on top of this fold like the teeth on a comb. And this is from 2001, one of my very first capsule endoscopy procedures. And I'm just mesmerized at the detail when we view this underwater. And that's the natural environment of the small bowel. It's filled, usually, with fluid. Each of these images in the esophagus, the stomach, small bowel, the colon, these are all underwater images. And that is why we have likened capsule endoscopy to that fantastic voyage of a submarine submerged in water traveling through the length of the GI tract. We get this 3D floating effect. It can be quite remarkable at times. Here, with the gas view, you see a lesion that looks fairly flat. And after water submersion, it's floating upwards. And you can see the individual villi, even see the vascular pattern of these villi. So the villi here are just collapsed. And they've been flattened by the gas distension. Sometimes, we can discover polyps that may be hidden in caves, such as the appendiceal orifice. Here's the gas view. Here's the water view. And in this video, you'll see that after infusing water into the lumen, we still see the AO here. But as we watch the AO now underwater, the lumen contracts. And this polyp crawls out of its cave and exposes itself to our view. Often, these AO lesions are SSAs. And so they are very flat. So underwater imaging with its floating effect facilitates identification of these flat polyps. Several randomized controlled trials have shown that underwater colonoscopy improves the Boston bowel preparation score. This is not surprising because we are using the water jet like a hose. And we're washing off the surface here. Here, you can see this adherent brownish mucus. It's fecal residue. But we can wash it off of the surface to expose the underlying mucosa. And this is so important to identify SSAs because they, too, can produce a mucus cap. So it really isn't surprising that many studies, randomized controlled, have shown that the ADR, the adenoma detection rate, is significantly higher using the underwater method. We also can use the water jet to interrogate tissue. So here, you can see a polyp growing along a fold and extending more proximally. Now, it floats into the lumen after water submersion. But we are interfacing with this lesion using the water jet to move the villus components around and to look in the valleys between the hills of the villi here. So it can be very helpful to identify pathology especially in a depressed lesion. EUS is an underwater imaging procedure. We focus on the ultrasound, so we don't think of it as an underwater procedure. But we need water for the acoustic coupling to the bowel wall. So we submerge the lumen. And this is a video from a time when I staged a lesion in the colon. And I noted, looking simultaneously at the endoscopic and the ultrasound view, that although the lumen was contracted, the muscularis propria stays round on the outside. And the bowel wall retains its native thickness. Normally, the thickness is somewhere between 4 and 5 millimeters. When you distend the wall with gas, it reduces to about a third of that thickness to maybe 2 or 3 millimeters. So essentially, we are converting a flat lesion, seen here with the gas view, a PARIS-2A type lesion, to an elevated lesion, a PARIS-1S lesion, as if we had injected in the submucosa to raise it up. So why is it that we get this floating effect? Well, it is the antigravity effect of water. But the submucosa contains a large amount of fat. The radiologists see that in the submucosa. They call this the black halo sign. And on EUS, that third layer of the submucosa contains fat. And that is why it is bright echogenic. You can see here the yellowish fat tissue in the submucosa after performing EMR. So this led to development of the UEMR method. The gas view, another example, appears PARIS-2A, very flat here, with the lumen quite distended with gas. After infusing water, water submersion, we get the underwater view. The lumen's contracted. It's raised. So now, we can easily lasso this raised lesion as if we had injected submucosally and perform en bloc resection. With one ensnarement, you can see the appearance afterwards. This is the lesion that was growing along a fold. But let's step back for a moment. Why do we even inject before we perform EMR? What's the rationale for that? Why do we do it? Well, it's conceptual. When we insufflate with gas, we distill the gas. When we insufflate with gas, we distend and thin the wall. And we will flatten the lesion. So to counter that effect, we perform submucosal injection to facilitate lesion capture, because it's been flattened by the gas, to reduce the risk of perforation and a transmural burn, because the wall is so much thinner. So that's the conceptual rationale for the submucosal injection. There are no data to support submucosal injection as beneficial or improving safety. There's just this one animal study that's always quoted, sick swine. And that doesn't come close to proving that submucosal injection decreases thermal injury to the deeper wall layers. In fact, using the hot biopsy forceps, there was no significant difference. Compared to using APC, there was a deeper burn when we have learned that APC is supposed to limit the burn to the superficial layers. When we go underwater, the lumen is contracted. This allows us to retain the native wall thickness, its consistency, its compliance, and the layers separate from one another, and allows us to capture a larger surface area. So our on-block resection rate can increase. And this is demonstrated in this video. You see a large LST. It's multilobulated. It's a 1S2A lesion close to the appendiceal orifice and the cecum. And we start with the gas view. It's about 4 centimeters in size. And if you were to resect this using conventional EMR method, it would definitely have to be piecemeal. I think all would agree with that. So now we're going to evacuate the gas. And we're going to replace it with water, with saline. We're using always saline. So now the lesion floats up. The lumen contracts. So it's occupying a much lesser surface area. And it allows us, using a 33-millimeter oval snare, to completely encompass the circumference of the lesion on the outer margins of the lesion and then apply cautery and perform on-block resection. So here you see the appearance after the resection. No bleeding. The layer of resection is more superficial. It's not as close to the muscularis propria as when you perform conventional EMR. So it's in the SM2 layer. And here you can see the scarring after the lesion on follow-up. So what can water immersion add to your practice? Well, it will improve the PrEP. And this, in turn, will improve the ADR. Better your PrEP, the higher the ADR. It may assist with difficult intubation. And why is that? There's less distention. And this, in turn, leads to less looping. It may lower your recurrence rates. Historically, recurrence rates have been in the order of 20% to 25%, some even as high as 50%. The recurrence rates with UEMR are generally below 10%. It may assist resection of recurrent or scarred and defiant polyps, polyps in difficult locations like the IC valve, the appendiceal orifice. But most importantly, enjoy the underwater view. Thank you very much. I might start the questions. Why do you think underwater hasn't taken off the way you might have hoped? I've heard your lecture on this now, I think, probably for 10 years, maybe. And is it a time thing? How long does it take you to fill up the colon with water? I don't think it's a time thing. If anything, as you get more experience, and this is, of course, applicable to so much of what we do in endoscopy, but with experience, you become more facile and the procedure becomes quicker. It's true that there is a learning curve. And initially, for example, intubation to the cecum will take longer compared to using gas. What's interesting is Doug Rex published a paper last year. What he compared was gas to total water endoscopy. And he found that with experience, there was a strong trend to shortening of that time to reach the cecum. And I think if you look at that learning curve, in my practice, for example, I'm convinced that water actually speeds up my ability to reach the cecum simply because I don't have a distended colon with loops. And so I don't have to apply abdominal pressure and all these other things I might with gas. But I think this is a mindset shift. It's almost like a paradigm shift, if you will, because we're used to using gas for everything we do in the GI tract. So now you have to switch to looking underwater. So imagine just walking around in our space now and we're looking through water like scuba diving or snorkeling. You have to interpret these images in a very different way, actually. So it's that shift, I think, that has caused it. And there's one other factor, and it's simply practical. In the colon, it just gets messy because the water starts to seep out. That's why I like the water exchange method, which is where I'm basically recycling the entire time. So whatever I'm infusing in, I'm sucking back out so that I don't have a net accumulation of water that will start to seep out from the rectum and, of course, it just gets messy and dirty. So I think these are all partly the reasons. It's a mindset shift. I mean, do you have to dress like a urologist? Yeah, I mean, sure. I'll put it this way. We do have some extra towels to soak up some of the fluid if you do have egress of some fluid there. But no, I mean, with time, you learn how to minimize that. And so I think that's the issue. In the upper GI tract, obviously, you have to be aware that there's a risk of aspiration. So if I do anything in the esophagus or stomach, I always inhibit these patients. I think in the duodenum, you don't need to necessarily inhibit. But yeah, these are just things that, very practical things that you think about as you get accustomed. Look, I don't want this to be a black and white thing. I use gas. And if I get bleeding, the view is cloudy. It's turbid, right? It's all red. I switch the gas on because I'm going to be able to achieve hemostasis much better with vigorous bleeding. Now, sometimes if it's just a little trickle, I actually will see the bleeding point better underwater, and I can target that. But it's not like I absolutely have to do everything now underwater. It's just another tool that we have in our toolbox. And so that's really the point of this lecture. Try it. Experiment with it. Become accustomed to these underwater views. I do use it routinely with any difficult intubation. And I just want to push on two other things. Perhaps you can share your diathermy settings via the text with everyone. Have you had to change those for underwater? And secondly, looking at that 4th centimeter. Yeah, so I've experimented. And clearly, the settings do have to be adjusted. The same as when I'm doing poem. I can't use the standard settings, and I can't use some of the settings that otherwise have been reported. Suffice it to say that you need to dial up, usually, your wattage to get a better cutting effect. And I will decrease the coagulation. I will maximize the cutting and minimize the coagulation effect. Coagulation will just kind of water bubbles a lot. So I'm actually using AutoCut. And I try to do an on-block resection. See, this is where I think things really speed up. I almost don't do any piecemeal anymore. I can usually get the lesions out now on block. But there are little tricks that help you get that on-block resection. You're taking advantage of the contraction of the lesion underwater. And you want to get that tissue. You want to maximize your tissue purchase in the snare. So you want as much of that tissue to float up into the snare as possible. So I'll do three things. And the first is what I call torque and crimp. So I'm torquing. I'm sort of pivoting the snare back and forth, maybe some to and fro. And all these little maneuvers, you watch. And you'll see the tissue rise up into the snare. And you can maximize that. The second is suction. And it's a gentle suction. When you're using water, you don't collapse the lumen immediately as you would with gas. So you can see the lumen, the lesion, kind of draw in. And I think that's very, very safe, as long as you're not too aggressive with that. So suction is number two. And the third is, I would actually wait for a contraction. Because it takes a leap of faith here. And again, it's a mindset thing. You just have to trust what you saw, what I saw, and what you would see on EUS if you had a midi probe. The muscularis propria stays round on the outside. It's not going to follow the involution. So as the lumen is contracting, and you close your snare, you're going to get more purchase area. You don't have to worry about perforation. The muscle will stay on the outside. Now, bear in mind, of course, if there is scarring, and there's a prior resection attempt, and there's fusion of the wall layers, that can change things. So be mindful of that. But if it's virgin, if you will, then yes, I think the risk of perforation is negligible. So Ken, this is Rob Enns. A couple of other questions. Do you worry about hyponatremia with all the fluid? Are there any electrolyte abnormalities? Yes. And that would be for excessive amounts of fluid that you're putting in. If you're concerned about hyponatremia, then use lactated ringers. By the way, I should emphasize that I have switched to using saline all the time. Now, I don't use distilled water or sterile water. I use saline. The reason for that is because if you use water, for some reason, I don't understand how this happens, but the water triggers the secretion of a mucus film. And this is both in the colon, where it really can impede your visualization, especially on the left side. For some reason, the cells on the left or the colonic epithelium on the left tends to secrete this mucus film more than on the right. At any rate, I noticed this. So initially, I was reluctant to use saline because I thought there might be a higher risk of thermal injury if I use saline, an ionic medium. And when I started using saline, though, I didn't see the mucus film anymore. So in Doug Rex's paper, they used water. They did not use saline. And he actually mentions in his paper that this mucus film, this whitish film, was an issue for them in terms of visualization and may have contributed to their low ADR, relatively low ADR. As you know, the study did not show that water was superior to gas. But that was maybe one. So that's just one small little thing can make a difference. So to answer your question, hyponatremia, as if you're dumping in liters and liters in your procedure in the upper tract, and it's going for hours or so, in the colon, you don't need to worry. How would you get hyponatremia in the colon?

water immersion

water exchange

colonoscopy procedures

underwater imaging

underwater EMR

hyponatremia