Hello again. I'm going to show you how to conduct the water pressure method. Basically water pressure method is a new technique of ESD, which we can open the sub-mucosal space utilizing the active pressure of the normal cell line. It is quite helpful to do renal ESD or colorectal ESD, but even for the gastric ESD case, which has relatively big region located at the gravity side, water pressure method is quite helpful. Therefore, using isolated pig stomach, I would like to show you how to conduct the water pressure method. Today I'm going to work together with Valeria coming from Mayo Scottsdale and Dr. Yamamoto together with me. Let's start the procedure. Before conducting the water pressure method, it's quite important to wash the lumen completely until it turns to clean. We should wash away the mucus and smudge from the lumen, and it becomes clean enough, we can start the procedure. I already washed the lumen, therefore I think it's good enough, then we should place the marking dot. Now I'm using 2.0 millimeter dual knife J, which is suitable for gastric ESD procedure. And before starting procedure, we should check the knife tip, could you open the knife? Because dual knife is a very short needle type device with small disc part, if it becomes very dirty, it doesn't cut well, and we cannot do anything with this device, therefore we should check the cleanness of the tip all the time once we introduce the dual knife through the working channel. Now it's clean enough, close it please. And this is multi-function device, which we can place marking dot, and we can make nice mucosal incision and sub-mucosal dissection, and of course we can inject additional fluid cushion through the knife by pressing the pedal of the injection. And at the same time, we can use the closed tip of dual knife in case of having minor bleeding during the procedure. So this is really helpful device. For the marking dot, we can just touch to the target tissue with the closed tip of dual knife, and for the human procedure, I usually use soft coag to place the marking dot. But this is pig stomach, I'm currently using forced coag, but for the human procedure, soft coag is good enough. Okay, placing marking dot here. Usually pig stomach has relatively thick mucosa, therefore it's a little bit tough to open the sub-mucosal space. Therefore, if the incision line doesn't open well, I would like to trace the same line a few times until it completely opens, then apply water pressure to open the sub-mucosal area. Okay. Where is, this is the marking, this is marking, this is marking, oh, it's still a little bit dirty, but it's okay, I'll try. Now it's connected, okay. Next step is injection. For the water pressure method, we usually don't use viscous agents such as orise gel or LW or hyaluronic acid solution, because we can easily open the sub-mucosal space. But if there is some fibrosis, we usually use hyaluronic acid solution, which was originally reported by Dr. Yamamoto. Okay, I'm introducing the olympus injection needle, okay, open it please, and come close to the target area, oh, unfortunately it becomes a little bit dirty, unclear, I'll flush the, yes, close it please, okay, open. And recognizing the marking dot, I usually puncture a few millimeter outside from the marking dot and start the injection, injection please, okay, because there will be some risk injuring the blood vessel within the sub-mucosal area when we conduct sub-mucosal injection, that's why I try to inject a few millimeter away from the marking dot, which is exactly on the incision line, okay, keep injecting, okay, stop it please, okay, wash away the dirty, break it, okay, once more again, injection please, okay, and we should check the lifting sign, and I always ask my assistant to count the volume of injection, like 0.5, 1, 1.5, 2, like this, because it's quite important to check the nice lifting sign during the injection process, and if target region doesn't lift up, usually needle itself already penetrates through the muscle area, okay, injection please, it's nicely lifting, it's good sign, okay, go ahead, go ahead, much more, okay, that's good enough, okay, move on to the distal side, okay, injection please, because the water pressure method can easily open the sub-mucosal space, therefore I usually complete the circumferential mucosal incision at the beginning, of course we can make a partial mucosal incision and quickly conduct sub-mucosal dissection, but mostly I complete the circumferential mucosal incision at the beginning of the procedure, it's much faster, okay, final injection around here, okay, injection please, oh, it's really sick mucosa, okay, injection, okay, it's nicely lifted up, okay, stop it please, needle in please, okay, let's switch to the Dual Knife-J, okay, it's already changed, then the target region is located the nice area, we can make a circumferential mucosal incision under air condition, otherwise we can perform circumferential mucosal incision with underwater condition, it's up to you, but by utilizing the underwater condition, we can visualize the target region much better because of the magnification effect of the underwater condition, therefore I suck the air completely, then immerse the entire area with the normal saline, and please remember that normal saline is mandatory to use it for this procedure because electric current doesn't transmit well if you use distilled water, it's really important, now I'm giving a lot of normal saline to the lumen, gastric lumen is relatively wide comparing with duodenum or colon, therefore it takes some time, but now it's already become underwater condition, it's time to start, okay, introducing the Dual Knife-J, air bubble is one of the problem of this procedure, but we can easily flush away the air bubbles by additional water irrigation, okay, knife out please, again check the cleanness of the knife tip, it's completely clean, then recognize the injected point, we can see the small opening here, so this is the right place to start the mucosal incision, gently touch to the target mucosa with the open tip of dual knife, but please don't push too much like this, white ceramic tip should stay on the surface all the time, now I'm using end cut eye, even end cut creates some bubbles, but it's okay, now we can see the blue sub-mucosal layer, that's a good sign, then continue the mucosal incision, oh, it caused lots of bubbles, usually it doesn't cause so much bubble, shall we decrease the effect, yeah, effect, this is effect too, so it caused a little thermal effect, yes, so effect is soft coagulation in between, so to avoid the bubbles, I step the foot pedal, then avoid the soft coagulation, I can use the power cutting, by stepping the foot pedal intermittently, I can use just cutting phase of the end cut. We have a question, what are the instances underwater ESD is better other than non-gravity dependent regions? When the region is located at the gravity side, it's the best option, and the region with severe fibrosis or region located at the angulated part, that is the good occasion which we use water pressure method, and best condition is in the duodenal ESD, I guess, yes, that's right, duodenal ESD and also colorectal ESD, those two are best option, now I'm catching the edge of the mucosal incision with the tip of the dual knife, it's very safe situation, carefully insert the tip to the mucosal edge, then catch the mucosa, and stepping the foot pedal of the cutting current, I can easily make a nice mucosal incision, I'm keeping the down angle and torquing my wrist to the right side, then knife tip goes to right side, it becomes a little bit dirty, therefore I would like to flush away the mucus from the operating field, then insert the tip to the incision line again, and continue the mucosal incision, we don't have to twist the shaft of the endoscope, I'm keeping the straight endoscope position, and just holding lightly with my right hand, and I always control both up-down and right-left channel together with my left hand, and torque my wrist gently to this side, then we can control the tip of the endoscope to the right side, again catch here, oh it becomes a little bit dirty, therefore it's really important to wash the mucus before starting actual procedure, I didn't have enough time to clean this stomach completely, mucus is really sticky, okay, if we can see the blue submucosa layer, it's a nice sign, and flush away the bubble, and check the marking dot, okay, this is the marking, and this is the incision line, oh it's overrun, but it's okay, clear visibility is always very important, I'm keeping down angle and torquing my wrist to the, oh it was slippery, but it's okay, this is another incision line on the left side going up, and slightly torquing my wrist, and check the incision line again, this area is a little bit slippery, but it's okay, I would like to connect this line, we have another question, spray and swift are non-contact coagulation electrical settings, do they have to change to change in underwater, and of course spray is mainly used for poem procedure? I usually don't use spray for the submucosa dissection, I usually use only swift coag for the submucosa dissection, for the water pressure method, we don't have to switch to the other setting, but because of the air bubble caused by the coagulation current, I sometimes use end cut even for the submucosa dissection, therefore we usually carefully check the submucosa layer, whether there is sick blood vessel or not, and if there is no sick blood vessel, we can use end cut for submucosa dissection as well, I think swift coagulation is a contact coagulation mode, yeah, the spray coag is non-contact, that's right, swift is contact, yes, and the spray is not suitable for the water pressure method, right, yeah, if we use spray, a lot of bubble, yeah, yeah, I think so, too much bubble, so this area that doesn't open well, therefore I would like to trace once more again until it completely opens, okay, I think it's connected, check it once more again, I think circumferential mucosal incision already completed, but still this is relatively shallow, therefore I would like to trace same line once more again, and if we can see the submucosa layer, we usually use coagulation current, at least for the human cases, because there will be some vascular network just below the muscular mucosa, that's why in order to avoid bleeding occasion, I usually trace the incision line a few times using swift coag, then we can widely open the submucosal space, now I'm tracing on the left side until it opens, okay, almost good enough, yeah, we can see swift coag cause more bubble, yes, that's right, that's another way, because of the poor manoeuvrability here, it goes to different tree, but we should, if we check carefully and keep outside from the marking dot, it's not a problem, okay, it's widely opens now, oh, this is a little bit remaining here, just cut here using okay, now it's completely opens, okay, I just completed circumferential mucosal incision, therefore it's time to start the submucosal dissection, usually creating the submucosal pocket, it's the challenging part for the beginners, even for the expert, if the target region located on the gravity side, it's sometimes difficult, but by using the water pressure method, we can easily open the submucosal space by brushing the normal saline to the incised area, therefore we can easily visualize the submucosal layer, and we don't have to go deep at the beginning of the submucosal dissection, just tracing the inner edge of the incised area like this, we can easily open the submucosal space, usually a few times tracing at the inner edge, just below the incision line, is usually good enough to widely open the submucosal layer, okay, this is second time, and I would like to trace once more again, right below the mucosal edge, we can easily open the submucosal layer, now it's time to go in, by utilizing the water pressure, we can easily open the submucosal layer like this, and this blue layer is the light dissection plane, usually I dissect one side from the bottom, within the submucosal layer, and we should focus on the edge of the remaining submucosal tissue, if we cut here, it much more widely opens, then following submucosal dissection becomes much easier. Another question, can you use clip traction method during the underwater ESD, even in the beginning, does it help? Yes, we can combine the traction method, but it's not necessary, we can easily open the submucosal space by utilizing the active pressure of the normal saline, that's why we are doing the water pressure method, it's a really safe and easy procedure, we can easily open the submucosal space like this, and recognizing the edge, I can easily open much more within the underwater condition, and if it is necessary, we can give additional fluid cushion at any time, and again, it is mandatory to stay on the surface, if we push too much like this, it's really dangerous, therefore, we should recognize white ceramic and blue band all the time, and if there is no visible vascular network, we can use endocut as well, or even for the submucosal dissection, then we can avoid air bubbles, we can easily open here, usually edge of the submucosal tissue is a little bit risky part to the submucosal dissection, but by using the water pressure method, we can easily open here, and brushing away the bubbles, it becomes completely clean, now I'm controlling right-left channel with my left hand, we don't have to twist too much, twist too much, and if it goes deep like this, we should pull back the knife a little bit, then at least it is staying on the surface, it's completely safe situation, again, checking the edge and the remaining tissue on the right side, I can easily open here, now I'm using a swift quag, and going back to the right side, and brush away the bubbles, and checking the edge again, and hook here, and hook the remaining tissue, and cut here from inside to outside, it's quite safe situation, again, hook here, and going inside to outside, usually dissected area becomes flappy, but by using underwater condition, it is quite easy to continue the submucosal dissection without having actual mechanical traction, okay, then brush away the bubble, now we can see the end point here, oh, still we have much more tissue, okay, let's go back to the right side, and hook the tissue from here, and go to left side, talking my wrist a little bit, then control right-left channel together with down angle, and I can easily go to the right side, left side, and checking the edge, okay, then hook this edge, and going to right side, when you use water pressure method, the bubble, mixture of the bubble is a big problem, yes, that's right, what is the tips to prevent the air bubbles, bubbles, one of the technical tip is using cutting current, especially end cut mode, even for the submucosal dissection, but as I mentioned, it causes bleeding, if there is vascular network, therefore we should carefully check the vascular network, yes, but bubble from the knife, yes, you're right, but I'm asking about the people unintentionally press the air button, and the bubble is like this, yeah, yeah, yeah, how do you avoid that, I usually don't touch any button during the procedure, just pressing the foot pedal, and controlling right-left channel, or up-down angle, that's all, so you don't press blue button at all, oh no, not at all, and of course if there are lots of liquid inside, and over distended, we should suck the liquid during the long-lasting procedure, we sometimes check the condition, and if it is over distended, we usually suck the liquid, otherwise we don't have to touch the bottom, I see, okay, now it is almost end, we can see the end point here, another question, yeah, the muscle layer seems to be far away, is it due to the water opening up the submucosal space, and not due to the dissection in the superficial plane of the submucosa, I intentionally injected a little bit larger amount of solution at the beginning, because of this is kind of demonstration, but for the actual clinical procedure, we can see the whitish muscle layer below this bluish submucosal tissue, I dissected the middle of the submucosal layer this time, but usually for the human clinical procedure, we actually see the whitish muscle layer below the bluish submucosal layer, so today a little bit shallower than the initial, yes, because initial step was a little bit difficult, because of the poor maneuverability this time, but even with the poor maneuverability, once we get into the submucosal layer, it becomes really easy and safe situation, and as far as we can see the blue submucosal layer, it is quite safe situation, because this knife has only 2.0 millimeter length, now it's completed, thank you very much. Okay, another question, what are the end cut settings when you use it for dissection? Usually for the human procedure, I usually use effect 2, duration 2, and interval 2, 2, 2, 2, that is my usual setting. Okay, but effect 2, the end cut effect is the coagulation in between, that's right, that's right, why do you use interval? Because when I make a mucosal incision, I would like to prevent the bleeding, that's why I usually use effect 2, but for the submucosal dissection, I prefer to use effect 1, as you mentioned. Okay. Okay, this is the basic technique of the water pressure method, usually the lumen is much cleaner than this, and we can easily recognize the muscle layer together with the remaining submucosal tissue. If you have any question, please feel free to ask us any question. No question so far. No question at all? Okay, thank you very much. Water is pumped through another bottle with a foot pump? It is a very important question. We usually use two pumps, one is for water irrigation through the endoscope, the other one is for injection through the knife. Therefore, I usually set two independent pumps, and one bottle has pure, normal saline without having blue color, and the other bottle has pure saline, and the other bottle has pure saline without having blue color, and the other pump for knife injection has blue colored normal saline, so we really need two different pumps. So we have two foot pedals. Yes. One is for the water jet through the scope, and one is the water jet through the knife. Yes, that's right, and we have another question. No, this is a correction, a foot pedal, not a foot pump. Okay, thank you very much for your important question. Okay, it seems all fine. See you. See you.

water pressure method

endoscopic submucosal dissection

ESD

porcine stomach model

normal saline

sub-mucosal space

washing the lumen