An interventional study of Underwater ESD (UESD) and Conventional Gas-Assisted ESD (GESD) in Colorectal Neoplasia, Colorectal Superficial Neoplasia and Colorectal Precancerous Lesions, sponsored by University of Roma La Sapienza. Completed at 1 site in Italy. Open to participants aged 19 Years and older. Per ClinicalTrials.gov, last updated 2026-03-31.
Sponsored by University of Roma La Sapienza · Not applicable, Interventional, and Treatment
Colorectal endoscopic submucosal dissection (ESD) enables en bloc resection of large superficial colorectal neoplasia but remains technically demanding and may be limited by suboptimal visualization, intraprocedural bleeding, smoke accumulation, and prolonged procedural time. Underwater ESD (UESD), performed under saline immersion rather than gas insufflation, has been proposed as a strategy to improve the operative field and facilitate submucosal dissection.
This prospective, multicenter, open-label, randomized controlled trial was designed to compare UESD with conventional gas-assisted ESD (GESD) for colorectal neoplasia referred for ESD across Italian tertiary centers. The primary objective was to assess non-inferiority of UESD versus GESD in terms of en bloc resection. Secondary objectives included comparison of histological resection quality, procedural efficiency, intraprocedural events, procedural field visualization, and post-procedural adverse events.
Colorectal ESD is an established organ-preserving technique for the en bloc resection of superficial colorectal neoplasia, particularly when conventional endoscopic mucosal resection is unlikely to achieve complete single-piece excision. However, colorectal ESD is technically demanding because of the thin colonic wall, unstable scope position, narrow submucosal space, intraprocedural bleeding, smoke generation, and difficulty in maintaining a stable dissection plane.
Underwater ESD has emerged as a modified operative environment in which luminal insufflation is discontinued and the target segment is immersed in saline. Saline immersion may improve visualization of the submucosal layer and of submucosal vessels, limit smoke persistence in the operative field, and facilitate more stable dissection. Although initial retrospective and comparative experiences have suggested procedural advantages of underwater ESD, high-quality randomized comparative data remain limited, particularly in Western multicenter practice.
This study was therefore designed as a prospective multicenter randomized trial across Italian tertiary referral centers to compare underwater ESD with conventional gas-assisted ESD for colorectal neoplasia referred for ESD. Patients were allocated 1:1 to either UESD or GESD. The primary endpoint was en bloc resection. Secondary endpoints included R0 resection, procedural time, dissection speed, intraprocedural bleeding, need for hemostatic forceps, smoke interference, vessel visualization, cutting-plane visualization, post-procedural pain, post-ESD coagulation syndrome, perforation, and delayed bleeding. The technical conduct of ESD apart from the assigned luminal environment was left to expert operator discretion in order to preserve real-world tertiary-center practice.
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Adults aged 19 years or older
Colorectal neoplastic lesion referred for endoscopic submucosal dissection
Lesion considered amenable to en bloc endoscopic resection by ESD according to expert pre-procedural endoscopic assessment
Written informed consent provided
Exclusion Criteria:
Known or suspected deep invasive neoplasia
Inflammatory bowel disease
Uninterrupted antithrombotic therapy
Known coagulopathy
Any clinical or lesion-related condition considered unsuitable for colorectal ESD by the treating endoscopist
Underwater endoscopic submucosal dissection was performed after placement of the lesion on the anti-gravity side whenever feasible, discontinuation of luminal insufflation, and filling of the target colonic segment with saline solution to obtain stable immersion of the operative field. After immersion, mucosal incision and submucosal dissection were completed according to standard ESD principles, using either a conventional stepwise or tunnel-based strategy according to lesion characteristics and operator preference. Only saline solution was standardized across centers; device selection, generator settings, and ancillary maneuvers were otherwise left to operator discretion. Hemostasis, when required, was achieved using hemostatic forceps.
Procedure: Underwater ESD (UESD)
Conventional colorectal ESD was performed under gas insufflation according to standard practice at each participating center. Mucosal incision and submucosal dissection were carried out according to standard ESD technique. Device selection, generator settings, and technical dissection strategy were left to operator discretion. Hemostasis, when required, was achieved using hemostatic forceps.
Procedure: Conventional Gas-Assisted ESD (GESD)
Underwater ESD (UESD) performed under saline immersion with luminal insufflation turned off.
Conventional colorectal ESD was performed under gas insufflation according to standard practice at each participating center. Mucosal incision and submucosal dissection were carried out according to standard ESD technique. Device selection, generator settings, and technical dissection strategy were left to operator discretion. Hemostasis, when required, was achieved using hemostatic forceps.
En bloc resection rate
Proportion of lesions resected in a single specimen.
Time frame: During the index procedure
R0 resection rate
Proportion of lesions resected en bloc with histologically negative lateral and vertical margins.
Time frame: During index procedure and histopathological assessment within 30 days
Procedural time
Time from submucosal injection to completion of lesion dissection.
Time frame: During the index procedure
Dissection speed
Rate of dissection calculated by dividing specimen area by dissection time.
Time frame: During the index procedure
Intraprocedural bleeding rate
Proportion of procedures with any bleeding occurring during ESD.
Time frame: During the index procedure
Use of hemostatic forceps
Proportion of procedures requiring coagulation forceps for active bleeding or prophylactic vessel coagulation.
Time frame: During the index procedure
Smoke interference
Proportion of procedures in which electrocautery-generated fumes/particulate matter impaired visualization and required repeated lens irrigation or temporary withdrawal.
Time frame: During the index procedure
Vessel visualization score
Operator-reported 5-point Likert score assessing clarity of identification of submucosal vessels during dissection. Lower scores indicate better visualization.
Time frame: Immediately after the index procedure
Cutting-plane visualization score
Operator-reported 5-point Likert score assessing clarity of the dissection interface between submucosa and muscularis propria. Lower scores indicate better visualization.
Time frame: Immediately after the index procedure
Post-procedural abdominal pain
Post-procedural pain assessed on a 0-3 numerical scale by nursing staff.
Time frame: 15, 30, and 60 minutes after the procedure
Post-ESD coagulation syndrome (PECS)
Proportion of patients with abdominal distension or pain at the resection site associated with fever or inflammatory response in the absence of documented perforation.
Time frame: Within 7 days
Perforation rate
Proportion of intraprocedural or delayed perforations.
Time frame: From procedure to 30 days
Delayed bleeding rate
Proportion of patients with clinically overt post-procedural bleeding or hemoglobin decrease \>2 g/dL without another source.
Time frame: From procedure to 30 days
Plan to share: Yes — Anonymsed data upon written and motivated requests
Supporting information: Study protocol, Sap
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University of Roma La Sapienza