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Shichijo et al. Mini-invasive Surg 2022;6:19 https://dx.doi.org/10.20517/2574-1225.2021.121 Page 3 of 13

Figure 1. (A) Disposable distal attachment (Olympus, Tokyo, Japan); (B) Black hood (Olympus, Tokyo, Japan); (C) ST hood (Small-
caliber transparent hood) (Fujifilm, Tokyo, Japan); (D) ST hood (Fujifilm, Tokyo, Japan); (E) Wavy Cap (Olympus, Tokyo, Japan).

Furthermore, various techniques have been developed.

Pocket creation method
Pocket creation method (PCM) was first reported by Hayashi et al. in 2014. The key to successful PCM is
[14]
the creation of a large submucosal pocket under the lesion using a transparent hood with a small-caliber tip.
Two advantages of PCM are (1) maintaining the thick submucosal layer with a minimal mucosal incision,
which prevents the leakage of injection solution; and (2) providing good traction, which facilitates efficient
submucosal dissection . A recent randomized controlled trial revealed that the ESD completion rate using
[14]
PCM was higher than that using conventional ESD . A detailed explanation of PCM is available in another
[15]
section by an experienced author.

Water pressure method
[16]
This technique was originally reported as an underwater ESD , or saline-pocket ESD . After creating the
[17]
mucosal incision, the patient’s posture was changed, whereby the lesion was positioned closest to the
ground to allow for water’s assistance. Next, the saline solution was infused into the dissecting submucosal
layer, with active pressure applied to the submucosal layer using the water-jet function of the
[18]
colonoscope . Not only using the floating force provided by saline solution immersion like underwater
ESD or saline-pocket ESD, active pressure to the submucosa facilitates good visibility of the submucosa, and
enables efficient submucosal dissection.

A retrospective study comparing water pressure ESD and conventional ESD for tumors with submucosal
fibrosis reported favorable outcomes of water pressure ESD . The median procedure time was significantly
[18]
shorter in the water pressure ESD group than in the conventional ESD (43.5 min vs. 72 min, P = 0.0041)
with similar proportions of adverse events. Its usefulness in duodenal ESD has also been reported [19,20] .