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

superiority to conventional ESD regarding en bloc resection, R0 resection, and dissection speed. Moreover,
even if colonic ESDs using PCM were not performed by highly experienced endoscopists but rather by less
[6]
experienced endoscopists, PCM resulted in better performance than conventional ESD . When performing
colorectal ESD with PCM, the ESD was completed using PCM without switching the strategy from PCM to
other methods, PCM results in less switching compared to conventional method. When performing
colorectal ESDs with PCM, it is not necessary for most endoscopists to consider changing their strategy of
ESD according to each situation during the procedure.

A key feature of PCM is that both traction and countertraction are naturally produced by the tip of the ST
hood in the submucosal pocket. The ST hood can stretch the submucosa at its orifice. This bidirectional
traction by the ST hood is different from the traction by other traction devices which pull up not only the
mucosa and the submucosa but also the muscularis unless countertraction such as insufflation or holding
the muscularis with an endoscope tip is applied. The muscularis can be visually identified through the
transparent wall of the ST hood and can be safely held with an edge of the ST hood. Therefore, endoscopists
can focus on cutting the stretched submucosa without concern for damage to the pulled muscularis.

[4]
The usefulness of PCM was also shown for duodenal ESD . PCM also facilitates extremely challenging ESD
cases such as duodenal ESD. The duodenal submucosa is much thinner and rougher than other organs.
Therefore, even if a viscous solution such as sodium hyaluronate is injected, the mucosal elevation cannot
last as long as in other organs. In particular, solution injected into the submucosa in the flat area between
folds may be dispersed quickly . The minimal mucosal incision performed during PCM prevents leakage
[11]
of the injected solution from the submucosa and the traction of ST hood stretches the thin submucosa in
the pocket. Recently, our retrospective comparison study showed that PCM facilitates ESD of gastric tumors
[12]
involving the pyloric ring . Even the prominent ridge of the pyloric ring can be overcome with PCM
during the submucosal dissection at the ring because undulation of the muscularis can be flattened using an
ST-hood tip put on the tip of an endoscope in the limited-space pocket. This feature is also useful to
overcome ridges of crescent folds in the colorectum .
[5]

PCM is still evolving. Some additional techniques using saline immersion have been reported to facilitate
performing PCM [13-16] . We know that some less experienced endoscopists may struggle to open the
submucosal pocket at the end of PCM because the more opened the pocket is, the more unstable the
[17]
endoscope tip becomes. Recently, we reported that a single reopenable clip facilitates opening the pocket .
Placing a clip to connect the specimen (after making the circumferential mucosal incision following
creation of the pocket) to the opposite wall produces traction to stretch the remaining submucosa around
the pocket. Single-clip traction is simpler and more economical than other dedicated traction devices .
[18]
CONCLUSION
PCM is recommended as a standard strategy not only for colorectal ESD but also for upper gastrointestinal
ESD. Although PCM has been established as an ESD strategy, it is expected that the use of traction
techniques will make PCM easier to perform.

DECLARATIONS
Authors’ contributions
Conception and design, drafting of the article, and final approval of the article: Hayashi Y, Miura Y
Drafting of the article, critical revision of the article for important intellectual content, and final approval of
the article: Lefor AK