Underwater endoscopic submucosal dissection (UESD) in saline offers several advantages
[1]
[2]. However, air bubbles generated during UESD can impair the visual field, particularly
when they accumulate in the hood. To address this issue, outlets can be introduced
on the side of the hood to facilitate air bubble removal [3]
[4]. Nevertheless, air bubbles accumulate in the hood in cases where the lesion is located
opposite to gravity, the tissue obstructs the air bubble outlet, or large air bubbles
form. This repeatedly necessitates the use of the waterjet function of the endoscope
to flush out the air bubbles. Under saline, air bubbles are generated by the evaporation
of saline caused by the energization of the electrosurgical knife, which creates a
“vapor pocket” that enables the knife to perform dissection [5]. Continuous high water pressure can make dissection difficult by hindering the formation
of a sufficient vapor pocket, whereas continuous low water pressure helps maintain
dissection power while minimizing and removing air bubbles. Therefore, we propose
the continuous low water pressure dissection technique (CDT), which helps maintain
the visual field during UESD ([Fig. 1]).
Fig. 1 Comparison of conventional dissection and continuous low water pressure dissection
techniques using a tapered hood with air bubble outlets in underwater endoscopic submucosal
dissection. a Buoyancy (yellow arrow) automatically removes air bubbles through the air bubble
outlets when the lesion is on the gravity side (blue arrow). b If the lesion is located opposite to gravity, the tissue obstructs the air bubble
outlet, or large air bubbles form, and air bubbles accumulate in the hood. c Backflow of water pressure using the waterjet can remove air bubbles through the
air bubble outlets. d Continuous low water pressure dissection technique. Dissection combined with continuous
low water pressure using the waterjet function of the endoscope minimizes and removes
air bubbles without the need to turn the waterjet on and off.
[Video 1] demonstrates UESD using a hood (ST hood short type; DH-29CR; Fujifilm, Tokyo, Japan)
with self-made air bubble outlets for a colorectal tumor. As half of the lesion was
located against gravity, air bubbles accumulated in the hood. The flushing pump setting
(OFP-2; Olympus, Tokyo, Japan) was adjusted from strong to weak after creation of
the mucosal flap, and CDT was initiated. CDT removed air bubbles that entered the
hood without the need to turn the waterjet on and off, thereby expediting the procedure.
Without changing the output of the Swift Coagulation (Effect 3, 30 W) in the electrosurgical
generator (VIO300D; Erbe, Tübingen Germany), dissection power was maintained ([Fig. 2]).
Underwater endoscopic submucosal dissection using a continuous low water pressure
dissection technique and a hood with four self-made air bubble outlets for resection
of a laterally spreading tumor in the cecum.Video 1
Fig. 2 Underwater endoscopic submucosal dissection using the continuous low water pressure
dissection technique and a tapered hood with air bubble outlets. a The laterally spreading tumor in the cecum was sprayed with indigo carmine. b As half of the lesion was located opposite to gravity, air bubbles accumulated in
the hood. c The continuous low water pressure dissection technique effectively minimized and
removed the air bubbles. d The flushing pump output (OFP-2; Olympus, Tokyo, Japan) was adjusted to the weakest
setting (yellow arrow) to maintain the appropriate water pressure for dissection power.
e The lesion was resected en bloc without perforation. f The resected specimen was sprayed with indigo carmine. Pathological examination revealed
high grade dysplasia (World Health Organization classification), measuring 60 mm in
size, with negative lateral and vertical margins.
In conclusion, CDT helps maintain the visual field during UESD, enhancing the usefulness
of a hood with air bubble outlets.
Endoscopy_UCTN_Code_TTT_1AQ_2AD_3AD
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