Fig. 1(A-C) The worst postulated sequence of possible events of endoscopic submucosal dissection. The bleeding occured just after the beginning of incision and dissection. The procedure was finally finished with frequent hemostasis with difficulty. The edge of incision was burned to be tough, and the entry of the devices into the submucosal layer was impossible beneath the incised mucosa, like a shell closing its husk. The entry into the submucosal layer was carried out from other mucosa, however the massive bleeding occurred during the dissection.
Fig. 2The structure of vessels in the gastrointestinal luminal wall. (A) The vessel network in the submucosal layer. The shallow mucosal incision just below the muscularis mucosae. Smooth incision with less hemorrhage is enabled, and the horizontal vessel network is seen through at the middle level of the submucosal layer. (B) The large vessels in the gastrointestinal luminal wall penetrate the muscle layer vertically and then inflow horizontally at the level of middle submucosal layer forming the ramified vascular network. In the area with high density of vessels, the faciae-like layer is formed with the ramified vascular network and the perivascular fibrotic tissue, and the layer containing fewer vessels and fibrotic tissue exists below the faciae and just above the muscular propria. Smooth dissection with less hemorrhage is enabled by maintaining the appropriate depth of dissection at the layer with fewer vessels and fibrotic tissue and by coagulating the penetrating vessels before dissection.
Fig. 3(A) An early stage gastric cancer in the posterior wall of body. (Ba) The horizontal vessel network in the submucosal layer is partially transected to reach the appropriate depth of dissection. The large vessels vertically penetrate the muscle layer and ramify horizontally at the middle level of the submucosal layer. (Bb) The ramified vessel network in the submucosal layer also connects the edges of incision. The certain dissection of this network allows the entry into the appropriate depth of submucosal dissection by broadening the groove made by the mucosal incision. (C) Once the appropriate depth of submucosal dissection has been obtained, the smooth dissection is enabled with first recognizing and properly dissecting the occasional penetrating vessels.
Fig. 4The difference of the density of vessels. (A) The extremely characteristic muscle layers named the oblique muscle layers are symmetrically seen in the anterior/posterior regions of the gastric body. The muscle layer is circularly absent at the inlet of the large vessel. (B) The density and thickness of the vessels in the gastric antrum overwhelmingly differs from those in the gastric body. (Ba) In the antrum, the density of vessel in the submucosal layer is low, and the fibrosis is also minimal, and these allow easy mucosal incision and submucosal dissection. (Bb) In the lesser curvature of the gastric body where the oblique muscle layers exist, as the blood vessels do not diverge frequently and the density of blood vessels are low as in the gastric antrum, the procedure is rather easy if the large penetrating vessels are not hurt by mistake. (Bc) On the other hand, in the anterior/posterior walls of the gastric body, where the oblique muscle layers exist, the greater curvature of the gastric body and lower rectum, the density of blood vessels is high and the diverged vessel network is inevitably hurt, if careful attention is not paid to the depth of mucosal incision and submucosal dissection.
Fig. 5Laterally spreading tumor: granular type in rectum. (A) Subtotal circumferential lesion. The anal side of lesion reached to the anal canal. The rectum, especially lower rectum and anal canal have largest blood vessels and also highest vessel density in the rectum. The shallow mucosal incision from the anal side was performed not to damage the vessels, and then the vessel network beneath the edges of incision was transected to reach the appropriate depth of dissection. (B) Bleeding does not occur if the dissection was performed beneath the horizontal vessel network while averting the penetrating vessels. The structure of blood vessels in the rectum was clearly recognized. The muscle layer is absent at the inlet of the large vessel in the shape of a wedge.
Fig. 6Quality controlled endoscopic submucosal dissection (ESD). (A) The technical tip to maintain the appropriate depth of submucosal dissection (upper). A shallow mucosal incision is performed not to cause bleeding. The horizontal vessel network is disclosed by dissecting the space between the vessels that can be seen through in the submucosal layer. After precoagulation and dissection of the vessel network to scoop up from the bottom of the vessel into the lumen, the edge of mucosal incision easily expands and the transparent hood itself can get into the submucosal layer and then a mucosal flap is formed. The technical tip to maintain the appropriate depth of dissection (lower). Once the blood vessels are damaged by mistake, the field of vision is lost and subsequent procedure becomes difficult, even after the appropriate depth of dissection has been obtained. The measure is to dissect with occasional local injection beneath the vessel network while maintaining the field of vision by the transparent hood. Especially, it is always necessary to distinguish the recognized vessels whether these are horizontal small branches of the vessel network or vertical large trunks of the penetrating vessels. (B) The resected specimen obtained by quality controlled ESD. The resected specimen contains thick submucosal layer including the whole vessel network in the submucosal layer. The appropriate depth of submucosal layer has most sparse and little electric resistance and the resected specimens are minimally injured by the coagulation.
Fig. 7Endoscopic submucosal dissection (ESD) of the lesions with severe fibrosis. (A) Laterally spreading tumor: non granular type in the colon. A mucosal flap was formed by dissection of the area with little fibrosis as much as possible after reaching the appropriate depth of submucosal dissection. The transparent hood could get into the submucosal layer despite the fibrosis because the appropriate depth of dissection has already been obtained. The fibrotic area can be safely and certainly dissected by dividing the muscle layer and lesions using the sheath of Flush knife and also connecting the lines of muscle layer at both sides. (B) The view after dissection of the fibrotic area and the resected specimen. The lesion was accompanied with severe fibrosis; however, the high-quality resected specimen was obtained with the entire vessel network. In ESD of lesion with severe fibrosis, it is important first to reach the appropriate depth of submucosal dissection (H&E stain, ×12.5).
Fig. 8The resected specimen of a case which was revealed to be outside the criteria. 0-IIc lesion in the posterior wall of the gastric body. It was diagnosed as a mucosal cancer and endoscopic submucosal dissection was performed. The resected specimen was obtained with thick submucosal layer containing all of vessel network. The submucosal invasion to the depth of 260 µm and lymphovascular invasion was recognized (H&E stain, ×40). If the dissection in the shallow submucosal layer was performed, these important findings might not be contained in the resected specimen and remain in the artificial ulcer of the resection site. If the vessel network was damaged and repetitive hemostasis was performed, these findings could not be recognized. These low-quality resection and specimen might lead to misjudge the case as curatively resected. M, mucosal; SM, submucosal; tub., tubular adenocarcinoma; ly, lymphatic invasion; LM, lateral margin; VM, vertical margin; EC, curativity C.
Fig. 9The resected specimen of a case which was confirmed to be within the criteria. The tumor invaded into the deep layer of the submucosa, but the muscularis mucosae covered this area without break (H&E stain, ×40). This was diagnosed as mucosal cancer. If the dissection was performed in the shallow layer of the submucosa and the muscularis mucosae was damaged, the specimen could be judged as massively invasive submucosal cancer with positive vertical margin of tumor. M, mucosal; tub., tubular adenocarcinoma; ly, lymphatic invasion; LM, lateral margin; VM, vertical margin; EA, curativity A.
Table 1Criteria of Endoscopic Submucosal Dissection in Esophagus, Stomach, and Colorectum
Table 2Treatment Results from June 2002 to May 2012