Gel immersion in endoscopy: Exploring potential applications

Table 1 Reports on gel immersion endoscopy for esophageal lesions

Ref.	Year	Article type	Gel/jelly type	Pathophysiology	Indication for gel immersion	Delivery procedure	Outcome	Obstacles for gel immersion
Nakano et al[27]	2021	Case report	OPF-203	Esophageal cancer	ESD; discomfort and irritability due to CO2 insufflation	Disposable forceps cap (manual irrigator)	No CO2 insufflation was needed, and ESD was successfully completed/the bleeding speed slowed down	-
Nakano et all[28]	2022	Case series	OPF-203	Esophageal cancer	ESD; 14 patients who underwent ESD for middle and lower thoracic superficial esophageal cancer	Disposable forceps cap (manual irrigator)	Completed ESD with en bloc and R0 resections achieved in 100%; No delayed adverse events
Ishikawa et al[29]	2024	Case report	OPF-203	Esophageal cancer	ESD; significant fibrosis	-	Successfully completed ESD combined with underwater method and applying gel immersion	-
Iwatsubo et al[31]	2023	Case report	OPF-203	Esophageal cancer	ESD; difficult to secure visibility	ERCP catheter (as an additional irrigation tube)	Achieved curative resection	-
Kato et al[32]	2021	Retrospective analysis	Lubricating jelly	Esophageal varices	Esophageal varices imaging quality/esophageal varices detection	14-Fr catheter	Imaging quality was superior than water-filled method. Using jelly resulted in clearer depiction of perforated varices
Sekiguchi et al[33]	2022	Case report	OPF-203	Esophageal varices	Rupture of esophageal varices	Forceps channel	Easily identified bleeding point	Decrease in suction pressure due to the gel viscosity
Hasebe et al[34]	2022	Case report	OPF-203	Esophageal varices	Rupture of esophageal varices	Forceps channel	Easily identified bleeding point	Subsequent EVL failed- EIS was succeeded
Sugawara et al[35]	2023	Case report	OPF-203	Esophageal varices	EIS; non-rupture esophageal varices	Forceps channel		Accurately evaluate varices needs to EIS

EIS: Endoscopic injection sclerotherapy; EMR: Endoscopic mucosal resection; EUS: Endoscopic ultrasound; EVL: Endoscopic variceal ligation; ESD: Endoscopic submucosal dissection.

Table 2 Reports on gel immersion endoscopy for gastric lesions

Ref.	Year	Article type	Gel/jelly type	Pathophysiology	Indication for gel immersion	Delivery procedure	Outcome	Obstacles for gel immersion
Miura et al[16]	2018	Case report	OS-1 jelly	Gastric tumor (lesser curvature of the antrum)	ESD; difficult to identify bleeding point	-	Successfully achieved hemostasis with electrocautery forceps	Need to replace the gel with gas before applying electrocoagulation
Miura et al[36]	2022	Case report	OPF-203	Protruded tumor at the anterior wall of the pylorus	EMR; immediate flow of water made underwater EMR difficult	-	Successfully achieved en-bloc resection	-
Kimura et al[37]	2022	Case report	OPF-203	Gastric neoplasm (greater curvature of the upper gastric body)	ESD	-	Successfully achieved en-bloc resection	-
Michigami et al[38]	2023	Case report	OPF-203	Metastatic gastric tumor (clear cell renal cell carcinoma; greater curvature of the gastric body)	EMR	-	Successfully achieved en-bloc resection	-
Khurelbaatar et al[39]	2022	Case series	OPF-203	Two cases with gastric tumor	ESD; difficult to identify bleeding point	Forceps channel irrigator (manual injection)	Easy to detect the bleeding point and ensuring clear field of view in both cases	-
Muramatsu et al[40]	2023	Case report	OPF-203	Gastric cancer at the pylorus ring	ESD; Difficult to identify bleeding point and tunneling	-	Easy to detect the bleeding point and successfully widen the tunnel and achieved en-bloc resection	-
Suto et al[41]	2022	Case report	OPF-203	Gastric cancer at anterior wall of the pyloric ring	ESD; the tumor was prolapsed into the duodenal side and difficult to identify bleeding point	-	Prevent further prolapse. Detection of the bleeding point resulted in successfully achieved en-bloc resection	-
Orita et al[42]	2023	Case report	OPF-203	Gastric varices at fundus of the stomach	Cyanoacrylate injection; difficult to secure the endoscopic visual field due to the massive bleeding	Forceps channel irrigator (manual injection)	Continuous gel injection gradually improved the visual field. A total of 4 mL of cyanoacrylate was injected into the varices over five tries	A total of 500 mL of this gel was used

ESD: Endoscopic submucosal dissection; EMR: Endoscopic mucosal resection.

Table 3 Reports on gel immersion endoscopy for duodenal and small intestine lesions

Ref.	Year	Article type	Gel/jelly type	Pathophysiology	Indication for gel immersion/study settings	Delivery procedure	Outcome	Obstacles for gel immersion
Miyamoto et al[43]	2021	Case report	OPF-203	Duodenal ulcer	Bleeding ulcer; unable to detect bleeding point	Water jet instrument	Successfully observe the ulcer in detail by filling duodenal lumen with the gel after hemostasis	-
Hayashi et al[44]	2022	Case report	OPF-203	Diverticular bleeding	Bleeding; unable to detect bleeding diverticulum, poor maneuverability	-	Maneuverability and field of view improved. The bleeding point was identified and successfully clipped for hemostasis	-
Jinushi et al[45]	2022	Case series	OPF-203	Duodenal ulcer in anterior surface of the duodenal bulb	Saline solution was quickly mixed with blood, making it difficult to identify the bleeding site	Secondary water delivery tube	Successful identification of the bleeding point was achieved, and hemostasis was accomplished with hemostatic forceps	There was only one forceps channel, making it impossible to insert both the gel and the hemostatic forceps simultaneously. Therefore, secondary water injection tube was used
Miyakawa et al[46]	2021	Case series	OPF-203	Two cases of SNADETs	Technical difficulty of the EMR procedure	Forceps channel	The lesion floated in the gel-filled lumen, while the muscular layer remained flat, allowing the snare to be performed more safely	Compared to a similar technique (underwater EMR); it is less cost-effective
Tashima et al[47]	2021	Case report	OPF-203	SNADET	The endoscope contacted with the lesion and started bleeding, due to the strong intestinal peristalsis	-	By using both saline and gel, the duodenal lumen expanded, allowing for a clear view of the entire SNADET	-
Yachida et al[48]	2022	Case report	OPF-203	SNADET	Water jet alone could not fill the lumen with saline	Forceps channel with auxiliary injection cap	The lesion floated in the gel-filled lumen allowing en-bloc resection safely	-
Kasai et al[49]	2023	Case report	OPF-203	Ampullary tumor	Perform EMR on the ampullary tumor with double-balloon endoscopy	Forceps channel with auxiliary injection cap	Gel was injected gel without bubbles; the lumen sufficiently expanded, allowing the ampullary tumor to be clearly visible	-
Miyakawa et al[50]	2023	Retrospective comparison study	OPF-203	SNADETs	Comparing gel-based EMR (GIER; n = 22) and Underwater EMR (UEMR; n = 18) in procedure time and R0 resection rate	-	GIER had a significantly shorter procedure time and a higher R0 resection rate compared to UEMR	The small sample size may pose a problem for statistical power, and the amount of water used in the UEMR group was not recorded
Amino et al[51]	2021	Case series	OPF-203	SNADETs	Evaluating en-bloc resection rate and procedure time of using under-gel EMR for six consecutive cases of SNADETs	Forceps channel	Under-gel EMR showed 100% in en-bloc resection rate and median procedure time was 6 minutes without any adverse events	-
Yamashina et al[52]	2022	Retrospective comparison study	OPF-203	SNADETs	Comparing gel-based EMR (GIER; n = 10) and Underwater EMR (UEMR; n = 14) in R0 resection rate, en-bloc resection rate, median procedure time, median amount of filling water/gel and adverse events	Forceps channel with auxiliary injection cap	Median procedure was shorter in GIEMR group. Median amount of filling water/gel was lesser in GIEMR group. There are no difference in adverse events rates	The small number of data points may lead to statistical instability; some patient data (such as chief complaints) might be missing
Tashima et al[53]	2022	Case report	OPF-203	ESD; a tumor adjacent to the papilla	Unexpected massive bleeding occurred during submucosal dissection, obscuring the lesion and bleeding point	Forceps channel	Organ collapse was maintained with lower intraluminal pressure, ensuring stable endoscope maneuverability and a good approach to the lesion, allowing safe submucosal dissection	-
Goto et al[54]	2023	Case report	OPF-203	Brunner’s gland hyperplasia in the duodenal bulb	Due to the tumor's large size of 30 mm, which was expected to hinder snaring, gel-immersion EMR was performed	Forceps channel	Expansion of the lumen facilitated snaring and allowed for clear visualization of the snare's engagement	-
Okamoto et al[55]	2024	Case report	OPF-203	Supra-ampullary adenoma	Cold polypectomy for 10 mm diameter lesion in supra ampullary tumor	Forceps channel	The gel-immersed lesion was captured with an endoscopic snare; the gel remained in place throughout the procedure and only 200 g was required	-
Tashima et al[56]	2022	Case report	OPF-203	ESD; duodenal epithelial tumor	Due to the thin duodenal wall, there is a risk of perforation during ESD	Forceps channel with auxiliary injection cap	As ESD progressed, the buoyancy effect became more pronounced, ensuring working space to make dissection easier. Additionally, it was easy to identify bleeding points was also simplified	-
Kawaguchi et al[57]	2023	Case report	OPF-203	EMR; intestinal polyp for patient with Peutz-Jaghers syndrome	The polyp stalk could not be observed well with CO2 inflation	-	By injecting gel, the polyp stalk became visible, allowing for successful snaring; Further gel injection helped manage post-EMR bleeding	-
Matsubara et al[58]	2024	Case report	OPF-203	EMR; intestinal (ileum) polyp	The small intestine did not expand with water (attempting underwater EMR) alone, making it difficult to secure a working space	-	Inflating the double-balloon endoscopy's balloon prevented backflow of a gel, allowing the lumen to expand adequately and leading to successful EMR	-
Horitani et al[59]	2024	Case report	OPF-203	Small intestine bleeding	Flushing the lumen with water resulted in the immediate mixing of water and blood, making it impossible to identify the bleeding point	Forceps channel with auxiliary injection cap	Inflating the tip balloon of the double-balloon endoscope helped retain the gel in place, allowing for the identification and successful hemostasis of the intestinal hemangioma	-
Tomita et al[60]	2022	Case report	OPF-203	EUS for jejunal tumor observation	Injecting water into the duodenum and small intestine resulted in quickly flowing out, leaving little water	Forceps channel	The gel remained near the jejunum tumor, clearly separating the jejunal wall from the tumor and enabling its identification	-

ESD: Endoscopic submucosal dissection; EMR: Endoscopic mucosal resection; SNADET: Superficial non-ampullary duodenal epithelial tumor; GIEMR: Gel immersion endoscopic mucosal resection.

Table 4 Reports on gel immersion endoscopy for colon and rectum

Ref.	Year	Article type	Gel/jelly type	Pathophysiology	Indication for gel immersion/study settings	Delivery procedure	Outcome	Obstacles for gel immersion
Yano et al[61]	2021	Case report	OS-1 jelly	Duodenal ulcer	Bleeding from ileocecal valve	Forceps channel with auxiliary injection cap	Successfully identified the bleeding point with double-balloon endoscopy	-
Teshima et al[62]	2022	Case report	OPF-203	Diverticular hemorrhage	Colonoscopy using gas insufflation and water immersion was difficult to secure the visual field	Forceps channel with auxiliary injection cap	Using gel ensured a clear visual field and allowed for the estimation of the bleeding point	A total of 600 mL of the gel was used
Suto et al[63]	2022	Case report	OPF-203	Diverticular hemorrhage	Despite flushing with water, the bleeding diverticulum could not be identified	-	The vessel within the smaller diverticulum was identified, and the site was successfully clipped	-
Abiko et al[64]	2023	Case report	OPF-203	Diverticular hemorrhage	Detecting of bleeding diverticulum could not be identified due to the large volume of clotted blood and severe active bleeding	Injected through long-hood	Gel retained within the long hood facilitated the detection of colonic diverticulum and enabled to identify the bleeding point, leading to successful hemostasis	-
Kobayashi et al[65]	2022	Case series	OPF-203	Case 1; diverticular hemorrhage; case 2 hemorrhoid	Bleeding point could not be identified with large amount of blood flow in two cases	-	Injection of the gel helped to identify the bleeding point in the diverticulum and successfully carried out endoscopic band ligation	-
Takada et al[66]	2022	Case report	OPF-203	Sessile serrated lesion	Under water EMR could not be performed due to the rapid mixing of bowel fluid from the terminal ileum compromised visibility	-	A clear view of the lesion margin was maintained and en-bloc resection was achieved	-
Kuwabara et al[67]	2022	Case report	OPF-203	EMR; protruded lesion extending into the diverticulum	Difficult to ensure sufficient buoyancy of the lesion	-	Under securing the sufficient buoyancy, the EMR had been succeeded	-
Jinushi et al[45]	2022	Case report	OPF-203	EMR; sigmoid colon polyp	Difficult to identify a bleeding point after underwater EMR	Secondary water delivery tube	Hemostasis with clips was achieved after securing a good visual field	-
Yoshimoto et al[70]	2022	Case report	OPF-203	EMR; Ileocecal valve polyp	To enhance the visibility of tumor located in the proximal lip of the ileocecal valve	-	Under-gel EMR was performed with a hexagonal snare; en-bloc resection was achieved without residual section	-
Yamamoto et al[71]	2023	Case report	OPF-203	Retrospective case series	Comparison between 6 cases of under-gel EMR with partial submucosal injection (PI) and 8 cases of under-gel precutting EMR among 348 patients with colorectal polyps	Forceps channel with auxiliary injection cap	En-bloc resection rate was 100% with under-gel EMR with PI, and 50% with under-gel precutting EMR	While it is a small, single-center retrospective case series, long-term outcomes were not assessed, and the quality of comparisons is low due to reliance on historical control data
Yamamoto et al[72]	2022	Case report	OPF-203	EMR; lateral spreading tumor-nongranular pseudo depressed type	Rapid mixing of fresh blood with water compromised visibility	-	Successfully achieved complete resection using underwater EMR, partial injection method and OPF-203	-
Tashima et al[73]	2023	Case report	OPF-203	EMR; flat elevated tumor within the diverticulum near the ileocecal valve	Perforation risk due to the tumor location of inside diverticulum	-	Gel immersion endoscopy secured a clear lesion margin view	-
Maruyama et al[74]	2021	Case report	OPF-203	ESD; nongranular-type laterally spreading tumor at the descending colon	The points of bleeding were not visible because of rapid blood collection	-	Successfully achieved multiple hemostasis with forceps	-
Tashima et al[75]	2022	Case report	OPF-203	ESD; anorectal tumor with hemorrhoids close to the dentate line	Hemorrhoids were scattered on the anal side of the tumor	-	The tumor’s buoyancy provided a good dissection field. Additional gel injection enabled immediate hemostasis	-
Nakano et al[76]	2023	Case report	OPF-203	ESD; laterally spreading tumor, granular-nodular mixed-type tumor	To improve endoscopic visual field and submucosal approach due to the buoyancy of the lesion	-	Easily approach to the submucosal layer and smooth creation of the tunnel owing to the buoyancy of the gel. Bleeding in the tunnel was clearly visible in the gel	-
Yamada et al[77]	2022	Case report	OPF-203	Postoperative anastomotic stricture	Due to the multifocal hemorrhage caused by the incision performed prior to balloon dilation	-	The incision was successfully continued, and the bleeding points were clearly identified	-
Yamamoto et al[78]	2022	Case report	OPF-203	Pediatric sigmoid volvulus	The poor endoscopic view caused by contaminated bowel fluid	-	Gel provided a clear endoscopic view and helped assess intestinal ischemia. The weight and pressure of the gel opened the twisted colon and facilitated volvulus passage in the left lateral decubitus position	-
Osera et al[79]	2023	Case report	OPF-203	EUS-guided puncture for rectal anastomotic obstruction	To identify puncture line under the EUS observation	-	Successfully punctured an obstruction site with 19G needle and made a dilation	-
Nomura et al[80]	2023	Case report	OPF-203	Colorectal stent insertion for colonic cancer	Poor endoscopic view due to severity of the stricture	-	Securing the visual field with gel and tapered tip of transparent hood	-

ESD: Endoscopic submucosal dissection; EMR: Endoscopic mucosal resection; EUS: Endoscopic ultrasound.

Table 5 Reports on Gel immersion endoscopy for hepatobiliary and pancreas

Ref.	Year	Article type	Gel/jelly type	Pathophysiology	Indication for gel immersion/Study settings	Delivery procedure	Outcome	Obstacles for gel immersion
Toyonaga et al[81]	2022	Case report	OPF-203	Ampullary tumor	Evaluation whether the ampullary had duodenal muscularis propria or intraductal involvement. Securing visual field during papillectomy	Forceps channel with auxiliary injection cap	Successfully delineate the ampullary tumor without invasion of the duodenal muscularis propria or intraductal involvement. En-bloc endoscopic papillectomy was achieved	-
Toyonaga et al[83]	2023	Case series	OPF-203	Ampullary tumor	Evaluating the delineation and diagnosis of 12 consecutive patients study who were used gel immersion under the EUS observation	-	Delineation of the ampullary tumors were achieved in all patients. The diagnostic accuracies of biliary spread, pancreatic intraductal spread, invasion into duodenal muscularis propria, and pancreatic invasion were 83%, 100%, 83%, and 92%	-
Toyonaga et al[84]	2023	Retrospective study	OPF-203	Hepatobiliary observational EUS (evaluation of ampulla)	Fifty-nine consecutive patients who received EUS with gel	-	Duodenal distention was excellent, good, and poor in 58%, 34% and 7% of cases. The delineation rates of the papilla in the axial and longitudinal views were 98% and 66%	Retrospective, single-institution study; Radial and convex linear-arrayed echoendoscopes were used; Diagnostic ability of EUS with for periampullary lesions remains unknown
Sato et al[85]	2024	Case series	OPF-203	Hepatobiliary observational EUS (evaluation of ampulla)	Retrospective case series study: EUS images of the Vater were taken for 10 patients, with 10 images captured after injecting water into the duodenal lumen, followed by another 10 images after applying gel in the same manner.	-	The number of excellent observations (as defined by Toyonaga et al[81]) was 0.4 ± 0.80 with water immersion, while it was 3.8 ± 1.99 with gel immersion, showing a significant advantage of gel immersion in the visualization of the papilla	Confirmation bias exists; Case series retrospective study
Yokoyama et al[88]	2023	Case report	OPF-203	Balloon enteroscopy-assisted endoscopic retrograde cholangiography for biliary atresia with biliary stones	Debris and blood obscured the visual field	Forceps channel irrigator	Visualizing bleeding site. Hemostasis was achieved	-
Okuno et al[89]	2023	Case report	OPF-203	Pancreaticojejunostomy anastomotic stricture and pancreatic stones	-	-	Gel immersion endoscopy successfully securing the visual field during radial incision and cutting	-
Fukushi et al[90]	2023	Case report	OPF-203	Obstructive jaundice in post Roux-en-Y reconstruction patient	Difficult to identify afferent limb in Rounx-en-Y anastomosis	-	Mixture of the gel and contrast media successfully identified the afferent limb of the patient and reached the duodenal papilla	-
Ogura et al[91]	2023	Case report	OPF-203	WON	To avoid mis-deployment of a lumen apposing metal stent caused by large amount of debris or necrotic tissue	-	Injected the gel into the lumen of the WON; Obtained good visibility of the lumen of the WON	-
Ogura et al[92]	2023	Case report	OPF-203	EUS-guided transduodenal drainage	To avoid double mucosal puncture	-	Succeeded EUS-guided transduodenal drainage without double mucosal puncture	-

EUS: Endoscopic ultrasound; WON: Walled-off necrosis.