Procedural outcomes of a novel underwater injection endoscopic mucosal resection technique for colorectal polyps ≥10 mm (with video)

Background and Aims It is uncertain whether underwater EMR (U-EMR) enables resection of the submucosal tissue with sufficient margins for T1 colorectal cancer (T1-CRC) because U-EMR forgoes submucosal injection. Therefore, we developed a novel ‘underwater injection EMR (UI-EMR)’ method that combines submucosal injection with U-EMR to obtain adequate vertical margin (VM). Patients and methods We retrospectively analyzed procedure-related outcomes of 135 consecutive lesions from patients who underwent UI-EMR for ≥10 mm, non-pedunculated colorectal polyps (median lesion size; 15 mm). The outcomes included en bloc, R0, RX, R1 resection rates and adverse events. Additionally, the VM distance of seven T1-CRCs was evaluated. Results En bloc resection was achieved in 127 lesions (94.1%). R0 and RX resection were observed in 92 (68.2%) and 42 lesions (31.1%), respectively, while R1 resection was seen in only one lesion (0.7%). We identified two lesions (1.5%) with adverse events, which were delayed bleeding. In T1-CRCs, all seven cases had free VMs, and the median VM distance was 1140 µm (range, 731-1570 µm). Conclusions UI-EMR safely demonstrated high success rates for en bloc resection, and potentially ensures sufficient VM. This technique might become an option, particularly for relatively small lesions concerning for T1-CRC and deserve further study.