Pay attention to a “window-blind” appearance of the distal rectal muscle layer during endoscopic submucosal dissection

 

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Endoscopic submucosal dissection (ESD) is increasingly used as a minimally invasive technique for treating superficial gastrointestinal tumors. Rectal ESD using the pocket-creation method (PCM) [1] is relatively easy for endoscopists who are used to performing submucosal endoscopy (e. g. peroral endoscopic myotomy [POEM]), even if they have not performed many ESD procedures.

Initially, creating the submucosal pocket is similar to the technique for POEM. However, there is a unique pitfall when performing distal rectal ESD. The inner circular muscle layer in the distal rectum has many transverse loose gaps between the muscle fibers. Submucosally injected fluid easily disperses outward through the gaps and widens them. We refer to this as a “window-blind” appearance ([Fig. 1]).

We must pay attention not to dissect in the clear area that looks like submucosa in those gaps. An outer longitudinal muscle layer may prevent penetration if damage to the circular muscle layer is limited to the region of the anus. However, perforation can occur if the circular muscle layer is damaged in the more proximal part of the distal rectum. To avoid damage to the circular muscle layer, it is important to maintain a tangential approach to the surface of the circular muscle layer and ascertain the depth of the submucosa when performing the PCM. The PCM does not need air insufflation to maintain the endoscopic visual field because the transparent hood with small-caliber tip easily maintains the visual field. Refraining from air inflation can make the submucosa thick and the rectal wall tangential ([Video 1]) [2].

Video 1 The window-blind appearance of the circular muscle layer during endoscopic submucosal dissection using the pocket-creation method for a distal rectal tumor.

The PCM therefore allows us to easily dissect the distal rectal submucosa without a reversal procedure. Although ESD in the distal rectum looks easier than in other areas, one must pay attention to the window-blind appearance to avoid damaging the muscle layer during ESD.

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• References

• 1 Hayashi Y, Miura Y, Yamamoto H. Pocket-creation method for the safe, reliable, and efficient endoscopic submucosal dissection of colorectal lateral spreading tumors. Dig Endosc 2015; 27: 534-535
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• 2 Hayashi Y, Yamamoto H. Pocket-creation method (PCM) for rectal endoscopic submucosal dissection (ESD). Intestine 2017; 21: 211-218
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