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Hayashi et al. Mini-invasive Surg 2022;6:7 https://dx.doi.org/10.20517/2574-1225.2021.125 Page 3 of 8

Figure 1. Sequence for the pocket-creation method (PCM) of endoscopic submucosal dissection (ESD). (A) An initial mucosal incision
is made away from the edge of the tumor after submucosal injection. (B, C) Creation of a submucosal pocket dissecting the submucosal
tissue under the tumor. (D) Opening the pocket from the gravity side, up to beyond the tumor. (E) Dissection of the side opposite
gravity in the same manner. (F) Completion of the ESD.

Advantages of PCM
Advantages of PCM include: (1) maintaining a thick submucosal layer because the minimal mucosal
incision prevents leakage of injected solution; (2) the endoscopic view facilitates recognition of the surface
of the muscularis because ST-hood traction in the narrow submucosal pocket stretches the submucosal
tissue to identify the correct dissection line just above the muscularis; (3) obtaining a high-quality
pathological specimen with a thick, less-damaged submucosal layer under the tumor; (4) adjusting the
orientation in the pocket to make the tip of the endoscope horizontal to the muscularis; and (5)
synchronization of the endoscope tip with fluctuations of the heartbeat and breathing in the pocket results
in visual stability.

Tips for performing PCM
Some tips facilitate PCM in practice. Some of them are surely useful for not only PCM but also most ESDs.

Aspirate the gas
Luminal insufflation is required to obtain a good endoscopic view in the gastrointestinal tract. However,
excessive insufflation interferes with endoscopic maneuverability. With PCM, however, luminal gas is not
necessary because the working space is the submucosal layer, and the endoscopic view is maintained by the
ST hood. Therefore, in PCM, good endoscopic control can be obtained by aspirating the luminal gas.
Collapsing the intestine by aspirating the gas in it makes the intestinal wall tangential [Figure 2]. Even a
vertical orientation can be changed to horizontal after aspirating the gas. Aspirating the gas keeps the
submucosa thicker and the endoscope tip more stable in the narrowed lumen [Figure 3].

The entrance should be distant from the tumor edge
The initial mucosal incision should be made distant from the tumor edge to achieve greater traction and
prevent mucosal-edge rolling. The specimen edge receives strong upward traction from the tip of the ST
hood upon entering the submucosal space. A shorter tumor-side edge undergoes little upward traction from
the tip of the ST hood. If the shorter edge is accidentally torn by traction, the tear will easily reach and