Underwater ESD vs CO2 ESD: A Northern Italian experience for a cutting edge technique

Aims Underwater technique in endoscopic submucosal dissection (U-ESD), has been recently introduced in order to facilitate submucosal layer exposition, compared to carbon dioxide ESD (CO2-ESD), in the most challenging settings, mainly by water pressure method and saline immersion (SITE). Methods We retrospectively enrolled 99 patients undergoing colorectal ESD in our center from September 2023 to October 2024, and divided them into two groups (U-ESD vs CO2-ESD). We therefore compared the two groups, assessing the following clinical outcomes: en bloc resection, completion, and curative resection (for pT1) rate, procedural time, perforation and bleeding rate and hospitalization time. Non parametric tests were performed with Mann-Whitney test and Fisher tests. Results We included and sorted 99 patients in two group: U-ESD group (n=49) and CO2-ESD group (n=50). The two groups were homogeneous in terms of median age [68 (IQR 16.5) vs 66.5 (IQR 16.25), p=0.6143], median lesion diameter [30 (IQR 20) vs 35 (IQR 31.25), p=0.069], median procedural time [75 min (IQR 54) vs 75 min (IQR 54.75), p=0.82] and lesion site (rectal n=15, distal colon n=14, proximal colon n=20 vs rectal n=25, distal colon n=16, proximal colon n=9). ESD completion rate was higher, but yet not significant, in the U-ESD group (OR 2,611, CI 0.5099-13.53, p=0.43), while no difference was reported in terms of en bloc resection (OR 0.97, CI 0,2731-3,498, p=0.99). We showed higher curative resection rate for pT1 lesions in the U-ESD group (OR 3.3, CI 0,6038 to 15,94, p=0.22). Both perforation (OR 2.143 CI 0,6676 to 6,733, p=0.35), the former not significantly, and bleeding rate (OR 4,325 CI 1,155 to 15,12, p=0.04) were higher in the CO2-ESD group. Median WBC count (11.30 x 10 9 /L vs 9.650 x 10 9 /L, p=0.21 and CRP levels (53 mg/L vs 30 mg/L, p=0.23) at 24 hours from the procedure were higher in the CO2-ESD group, but not significantly, reflecting the poor predictive value of these lab tests. Eventually, median hospitalization time resulted markedly lower in the U-ESD group (1 day vs 3 days p=0.0078). Conclusions Our study confirmed that underwater approach in colorectal ESD leads to safer procedures and shorter hospitalization. As a consequence, we propose SITE as both clinically beneficial and cost-effective. Further multicenter and randomized studies are required in order to better assess clinical outcomes of this cutting-edge revolution in third space endoscopy. Publication History Article published online: 27 March 2025 © 2025. European Society of Gastrointestinal Endoscopy. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany