Lesion isolation by circumferential submucosal incision prior to endoscopic mucosal resection (CSI-EMR) substantially improves en bloc resection rates for 40-mm colonic lesions

Background and aims: En bloc resection is preferred for colonic laterally spreading tumors, but is limited to 20 mm with endoscopic mucosal resection (EMR) using normal saline submucosal injection. Our aims were to compare the efficacy and safety of circumferential submucosal incision prior to EMR (CSI-EMR) versus conventional EMR for en bloc resection of artificial lesions 40 x 40 mm in size using submucosal injection of succinylated gelatin in a porcine colon model. Subjects and methods: Two areas of normal rectosigmoid mucosa measuring 40 x 40 mm were marked with soft coagulation for en bloc resection in each of 10 pigs. By alternate allocation, one was removed with conventional snare-based EMR following submucosal injection of succinylated gelatin. The other was circumferentially incised using an insulated-tip knife, followed by submucosal succinylated gelatin injection followed by EMR of the isolated area. All procedures were performed by a single endoscopist with significant experience of EMR but none of endoscopic submucosal dissection (ESD). Euthanasia and colectomy were performed on day 10. Specimens and ex vivo colon resection sites were examined by a specialist gastrointestinal histopathologist blinded to the technique used. Results: En bloc excision rates were 70% for CSI-EMR vs. 0% for conventional EMR (p = 0.016). The median number of resections was 1 (interquartile range, IQR: 1-2) for CSI-EMR vs. 4 (3-6) for EMR (p < 0.001). Mean specimen dimensions were 50 x 43 mm for CSI-EMR vs. 37 x 32 mm for EMR (p = 0.001). Overall procedure duration (mean +/- SD) was 30.3 +/- 19.8 minutes for CSI-EMR vs. 12.4 +/- 6.8 minutes (p = 0.003) for EMR. The mean duration of the final 5 CSI-EMRs was 17 minutes, with a statistically significant learning effect r = -0.7, p = 0.025. No perforations or bleeding occurred. All animals were euthanased on day 10. Histologically, CSI-EMR resulted in larger specimens and deeper submucosal resections. Conclusions: CSI-EMR with submucosal injection of succinylated gelatin is safe and superior to conventional EMR, consistently resulting in en bloc resections larger than 50 x 40 mm. With experience, total procedure duration is