Intraprocedural bleeding (IPB) represents a major challenge in third-space endoscopy (TSE), as it prolongs procedure time, impairs visibility, and may negatively affect clinical outcomes. Amber-Red Color Imaging (ACI) is a novel imaging modality designed to enhance visualization of vascular structures and bleeding sources, potentially improving the safety and efficiency of TSE procedures. This study aimed to systematically evaluate the incidence of major IPB and the frequency of prophylactic vessel coagulation during TSE using the ACI mode.

In this single-center, video-based analysis, consecutive TSE procedures (ESD, POEM, G-POEM) between February and October 2025 in which submucosal dissection was performed  with the ACI mode were reviewed. The primary endpoint was the frequency and duration of major IPB. Major IPB was defined as a bleeding episode requiring either multimodal endoscopic hemostasis, lasting >1 minute or leading to complete loss of visibility (“red-out”). Secondary endpoints included the rate of prophylactic vessel coagulation—defined as the preemptive coagulation of visible vessels using knife or coagulation forceps before dissection (“vessel sealing”)—and the occurrence of postinterventional complications.

A total of ten full-length videos of TSE procedures (4 ESDs, 3 POEMs, 3 G-POEMs) were analyzed. The median procedure time was 79.5 (43–171) minutes. For ESD cases, the median lesion size was 50 mm (41–97). Five major IPB events were observed, all during ESD (1 gastric, 1 esophageal, 3 rectal). The mean duration of IPB until successful hemostasis was 47.8 ± 53.6 seconds. A total of 41 prophylactic vessel coagulations (vessel sealing) were performed, corresponding to a mean of 5.3 per procedure. The mean duration of each vessel sealing was 39.3 ± 39.5 seconds. The success rate of prophylactic coagulation—defined as absence of subsequent bleeding—was 90.2%. No postinterventional complications occurred.

In this single-center cohort, the incidence of major intraprocedural bleeding under ACI guidance was very low. This may be related to the high success rate of prophylactic vessel coagulation. Further prospective, multicenter studies are warranted to determine the clinical benefit of imaging modalities, such as ACI, compared to standard white-light endoscopy.