Today, clip artifact on the ASGE SUTAB tip of the week. Last week we talked about finding EMR scars and this week the topic is recognizing non-neoplastic change on EMR scars that results from prior clip placement. So my own classification of this is type 1 inflammatory nodules at the base of retained clips, type 2 inflammatory nodules after the clip has fallen off, and then type 3 non-inflamed polyploid tissue that results from prior clip placement. There are three types of clip artifact that we'll encounter during examination of EMR scars at follow-up. The first is where the clip is still attached and around the base of it there's a mound of inflammatory tissue. It's often red. There may be some white granulation tissue right at the base of the clip. The pits on this tissue are typically fairly uniform in size but larger than normal colonic pits. The second type is the same tissue but now the clip has fallen off and there usually is inflammation and white light. It'll look red in narrowband imaging. It looks brown. The pits are uniform in size but larger than normal colonic pits. There may be some white ulceration on the tip of this mound. The third type are mounds of tissue that have normal mucosal color and the pit structure is typically the same as normal colonic mucosa and I think this can result from a couple of causes. One is the resolution of this inflamed tissue that was around the base of the clip especially the larger mounds of tissue may result from that and the other mounds are often just a result of distortion from the effect of the clip drawing mucosa together and then healing in a deformed shape. Here is what I hypothesize as phase one in the development of clip artifact. We have a retained clip and it's got a mound of inflammatory and granulation tissue around it. That white tissue is granulation tissue. If you biopsy that you're going to get ulcer but off to the left of that you see that red area there the mucosa is intact but the pits are enlarged and they are relatively uniform in size. That is not recurrent polyp. This is all inflammation and granulation tissue at the base of a clip. I usually include this material in the biopsied tissue when I'm biopsying a scar but I don't separate it into a different bottle. I feel very confident that it's not residual polyp and we just lump it in with biopsies of the flat scar. Overall here there is no evidence of residual or recurrent polyp on this EMR scar. I'm not suggesting that every clip develops a big mound of granulation tissue and inflammatory tissue around its base. Here's a scar near the ICV with three clips on it and none of them has this big mound of tissue around it. So there's a lot of individual variation in how much of that tissue develops may be part of the reason why we see variation in how much clip artifact is present at follow up of EMR scars. Here is phase two of this process of clip artifact formation. This is exactly the same as phase one except the clips are gone and we can still see these mounds of inflammatory and granulation tissue and eventually in the absence of the clips these areas of inflammation will turn into benign appearing mucosa but still nodular. That will be phase three. Before we discuss the next phase of clip artifact I want to make a point about the pit structure in the actual scar itself because we're going to come back to it from time to time in subsequent videos. But it can be very confusing. If you look at the area between these arrows there are pits that have pretty good sized blood vessels around them and you might think that there is residual adenoma. There isn't a discrete margin to it. In general the pits are uniform in size. That's one of the features that you will see but those pits tend to be bigger than the surrounding normal mucosa depending on the phase of healing that the scar is in. So that's important to understand in the interpretation of scars. There can be color changes in the actual scar itself and the pits may be larger but they tend to be fairly uniform in size and shape. Here is phase three the final phase in the development of clip artifact. The inflammatory changes are gone and we're just left with a mound of benign normal mucosa. We should confirm that it's normal by looking at it in magnification and with narrow band imaging or whatever tool we have for electronic chromo endoscopy and confirm that the pit pattern is normal. Looking at these mounds of clip artifact designated by the arrows you can see that the pit pattern is basically normal. You have the tiny white pits of normal colonic mucosa and between the yellow lines the general area of the scar. Notice that the pits are somewhat larger even though this scar is completely healed up but still they are uniform in size and this is something that we need to get used to looking at is this slight change in the pit pattern of the scar itself depending on its phase of healing and its age. Here's another example of mature clip artifact phase three in this process of clip artifact development but the nodules of clip artifact are not as prominent as they were in the last case and we're going to see all variations of size and shape of clip artifact. When we look with narrow band and close focus which we should do in every case you will see that the pits are normal. Notice right along the scar the pits are slightly larger in this mature scar than they are on the nodules of clip artifact or in the surrounding normal mucosa but still they're very uniform in size nothing that suggests here recurrent polyps. So one of the key skills to develop in looking at these scars is the ability to distinguish clip artifact from recurrent polyp. Even when the scar looks perfectly normal I still typically biopsy at some controversy as to whether this is necessary with the optics that are present on modern scopes but I will just say for the purposes of this that you can sort of by biopsy the nodules of clip artifact and including them with your scar flat your flat area scar biopsies again I don't put them in a separate bottle but when you come back for the next follow up the clip artifact will be less prominent so you can sort of pull it off and the scar will heal in a flatter confirmation. The key feature of the last phase of clip artifact formation is that the little mounds of tissue are not inflamed at this stage I think it's impossible to know whether these mounds of tissue especially when they're flat are the residual of what was previously an inflamed mound at the base of a clip or if they're just mucosal distortions adjacent to clip sites. Here's an EMR scar opposite a tattoo and we can see all three types or phases of clip artifact on the right a still adherent clip with a mound of inflammatory tissue at its base on the left two red inflamed nodules where one or perhaps two clips have recently detached and the tissue is still inflamed and then below that we see little mounds of basically normal mucosa where the mucosa shape has been distorted by the pressure of the clips so depending on when we look at the scar and at what time clips have fallen off we can see three different types of clip artifact we want to be able to distinguish all of them from recurrent or residual polyp. Again using the same lesion highlighting the three types of clip artifact that we encounter the yellow arrow is pointing to a mound of inflammatory tissue with larger inflamed pits at the base of a still retained clip the red arrows are pointing to two inflamed mounds with dark tissue and NBI and still quite large pits this is where a clip or a couple of clips have recently disengaged and the inflammation is still present and then the blue arrows pointing to these mucosal distortions where the pit pattern is actually completely normal this is the most mature kind of clip artifact that we encounter in this particular case we can see all three types and I also want to call your attention to the purple arrow pointing right to the middle of the upper part of the scar and notice there that the pits are uniform in size but they are larger and in general there is a darker color compared to this distorted mucosa where the blue arrows are where the pit pattern is really normal notice how similar the pits in the base of that scar are to the inflammatory pits pointed out by the yellow arrow at the base of the clip again we want to be able to distinguish that all of this tissue is non-neoplastic as a prelude then to identifying recurrent polyp on EMR scars we've talked about recognizing non-neoplastic tissue on EMR scars first of all clip artifact changes nodular changes that result from prior placement of clips and three types of that and then alterations in the pit pattern in the flat scar the fact that those pits can be larger those still typically uniform in size relative to other pits in the scar generally larger than the pits that are in the normal colonic mucosa next week identifying recurrences on EMR scars on the ASGE SUTAB tip of the week

clip artifact

EMR scars

inflammatory nodules

pit pattern

recurrent polyp