We're looking at an endoscopic mucosal resection defect immediately after on block resection using traditional EMR, that is inject and snare resect. Also an on block resection of a serrated lesion about 18mm in size that had some worrisome features in the center of it and so an on block resection was performed. We're looking at the EMR defect. The question is what does this white area in the center represent? The correct answer is type 1 muscle injury. So the white area is muscle that we have exposed and that's the definition of type 1 muscle injury. It's a bit of a misnomer to call it an injury because all you have to do is expose it and it's a type 1 muscle injury. Although the muscle may not actually be injured, it may just be exposed so that you can see it. So the rest of the semicosal defect is stained blue that is the we can see the typical staining of the semicosal but we've cut deep enough close enough to the circular muscle layer in the white area that we've exposed the muscle. Type 1 muscle injury does not necessarily need closure. If you think the muscle is injured it is best to close it close it with hemostatic clips or other devices but it's important to recognize that this is the circular muscle that you've exposed at the so called type 1 muscle injury.

endoscopic mucosal resection

traditional EMR

on block resection

serrated lesion

type 1 muscle injury