Improvement in the Visibility of Submucosal Layers and Vessels with Amber-Red Color Imaging in Colorectal Endoscopic Submucosal Dissection

Background and Aim: Amber-red colour imaging (ACI) (Fujifilm), a novel observational mode, was developed to visualise submucosal vessels. This study evaluated vessel and submucosal layer visibility using ACI during colorectal endoscopic submucosal dissection (ESD). Methods: This observational study reviewed consecutive patients undergoing colorectal ESD from January 2021 to June 2025. Therapeutic outcomes of 72 ACI cases were compared with 505 white light imaging (WLI) cases. The primary outcome of this study was the mean number of intraoperative bleeding (IB) events during ESD between cases with ACI and those with WLI. The secondary outcomes were various therapeutic outcomes of ESD. Additionally, fifteen endoscopists from four countries (seven experts, eight non-experts) evaluated the visibility in ACI and WLI images during ESD using a four-point scale (Score 1 = poor to Score 4 = excellent). Results: Among 72 cases (mean age: 67.3 ± 11.9 years, male proportion: 48.6%), the en bloc resection rate was 98.6%. The ACI group showed fewer IB events than the WLI group (2.0 ± 2.5 vs 2.7 ± 3.4, p = 0.040), significant only among non-experts (1.5 ± 2.0 vs. 2.6 ± 3.1, p = 0.009). Regarding image evaluations, ACI achieved higher visibility scores (median [interquartile]) for vessels (4 [3–4] vs. 3 [2–3], p < 0.001), submucosa (4 [3–4] vs. 3 [2–4], p < 0.001), and muscle layer (3 [2–4] vs. 2 [2–3], p < 0.001). The rates of Score 3 + 4 for vessels, submucosa, and muscle layer were significantly higher in ACI than those in WLI regardless of endoscopists experiences. Conclusion: ACI may contribute to enhance the safety of colorectal ESD by reducing IB and improving the visibility of vessels and submucosa.