This study demonstrated that the use of DESP and the flexible grasper (Ig/IgE) allow for the removal of large polyps in the right colon with a significantly shorter dissection time, total procedure time, and fewer injuries than standard ESD technique in an ex vivo porcine model. Moreover, IgE provided a broader reach of the grasper and decreased ESD procedural times and submucosal injection volumes. Finally, this surgical platform and these tools may help bridge the gap of skills in ESD procedures between the expert and the novice.
In order to access the more proximal colon, endoscopes and devices pass along the outer side of the intestinal curves and loops, leading to limited access to inner lesions, especially lesions located just beyond the splenic flexure and the hepatic flexure.[17] In this study, the Ig instrument could not reach behind each flexure. Moreover, the same difficulty also occurred in the ascending colon, the transverse colon, and the descending colon since the overtube device itself made the wide intestinal arch. The elbow bending function can resolve this issue, allowing the IgE to reach everywhere in the large intestine.
In this study, each procedure was able to successfully reach the cecum. Navigation of the colonoscope equipped with DESP may be more difficult as it required assistance with abdominal pressure, unlike standard colonoscopy. However, the simplified colon model does not allow demonstration of the advantages of the balloon technique that assists navigation under more challenging situations.[18] Similarly, the advantages of the double-balloon platform to improve the endoscope operability in the right colon were not demonstrated in this simplified model.[15] [19]
Traction devices have been introduced to provide tension and counter-tension to facilitate resection of larger lesions, more complex lesions, and lesions located in difficult locations. However, few traction devices can be used anywhere in the large intestine, provide real-time dynamic traction in all directions, and move independently from the endoscope, allowing for continuous direct visualization of the target plane of submucosa. The S-O clip (Zeon Medical, Tokyo, Japan), traction wire (ProdiGITM Traction Wire, Medtronic, Ireland) and elastic band (Elastic Traction Device; Micro-Tech Endoscopy USA Inc, Ann Arbor, Mich, USA) can be used in the right colon and provide traction in all directions, but it cannot be repositioned during the procedure.[20] [21] The clip-nylon method and the suture/clip method utilizing the FB of the double-balloon interventional platform (DEIP) can provide real-time traction, but only in a single dimension, proximal and distal/back and forth.[19] [22] [23] Robotic platforms have not been applied to the right colon yet, though new technology might solve this limitation.[24]
The dexterity of IgE led to significantly shorter dissection time and shorter total procedure time compared to using Ig. First, IgE was able to reach the targeted site, even the inner side at the ascending colon which was out of the Ig’s reach (Figure. 3c). Second, despite the slightly longer grasping time of IgE (Ig vs. IgE = 1.5 vs. 1.9 min), IgE could provide more traction per grasp using both elbow bending and tip articulation, leading to better visualization and reducing the number of regrasping. This novel traction method may also be particularly helpful for lesions suspected to have submucosal invasions, mucosal lesions with fibrosis, residual/recurrence lesions after incomplete endoscopic resection, and non-polypoid colorectal dysplasia with inflammatory bowel disease; these lesions are difficult to lift due to their submucosal fibrosis.[14] [25]
This flexible grasper was not used during mucosal incision; in fact, there was no significant difference in mucosal incision time between the three techniques. This grasper has the potential to make mucosal incision easier by providing stability and tension, as observed with endoscopic models of robotic surgery.[24] Using the grasper during mucosal incision may further emphasize the benefits of this instrument. Moreover, the use of an additional knife/scissors in combination with IgE might also be helpful. These multi-instrument techniques should be investigated further. After tumor resection, closure of large mucosal defects (>20 mm) in the right colon is recommended.[3] We believe the ease of mucosal closure would also greatly facilitated using the grasper to approximate the two edges of the defect.[26]
In the United States, ESD has been less widespread, compared to East Asian countries, since the relative lack of gastric tumor cases forces endoscopists to start with the more challenging colorectal tumors, leading to the increased risk and a longer time to acquire skills in ESD. In our study, there was no difference in ESD procedural outcomes using DESP + IgE between the experienced and the novice groups. The novice could perform ESD efficiently and safely as well as the expert. This surgical platform has the potential to bridge the gap between the expert-novice differences, and shorten the learning curve of ESD.
There are several limitations in this study.
(1) A synthetic colon, which keeps the shape compared to human colons, was used to investigate the reach of Ig/IgE. The function of Ig/IgE might be underestimated since we could collapse the colon clinically in grasping the tissue. Nevertheless, we experienced Ig wasn’t able to reach the lesion in certain locations.
(2) The ex-vivo model in this study has no peristalsis or bleeding, so performing ESD may be more difficult clinically. On the other hand, the simplicity of the model may underestimate the benefits of DESP and IgE grasper. A similar double-balloon platform, DEIP, is clinically used in the right colon and has demonstrated the benefits of the double-balloon platform in navigation. Traction devices have also been used for ESD and demonstrated clinical advantages.
(3) All lesions were 4 cm in diameter and placed at the posterior wall of the ascending colon to limit variability. The use of this traction device will need to be evaluated for resection of other challenging lesions and lesions at other challenging locations, such as circumferential lesions or lesions at the hepatic flexure or under a fold.
(4) No other traction comparator was done. In addition, normal saline was used as a submucosal injection fluid, not a long-lasting gel. The need for repeated injections with longer procedures is exaggerated with the use of short-acting injection fluid. Additionally, the need for repeated injections further increases the total procedure time.[27]
(5) All participants are advanced endoscopists and participants familiar with the ex-vivo research model and using this endolumenal platform. Therefore, this study didn’t investigate the learning curve of this platform.[9] Our previous study showed the experience in five ESD procedures might be enough in an ex-vivo model.[16]
(6) This was a preclinical study. Larger human feasibility studies are warranted to validate these results.
In conclusion, we demonstrated a novel flexible grasper with DESP likely represents an important traction tool for removal of large pseudo-polyps in the right colon. This new technology has the potential to expand the capacity for endolumenal resection, leading to lower colectomy rates for complex polyps.