endoscopic subcausal dissection of giant circumferential laterally splitting tumor and closure. Large lateral splitting tumors are seen in all segments of colon, particularly in the rectum. Surgical approach might lead to adverse events such as leakage or permanent stoma. In EMR recurrence is high, especially in large lesions. EST for large lesions has procedural challenges and risks such as post-procedural bleeding and stricture formation. Treating large lesions has several challenges. Preoperatively defining margins and staging can be difficult. This can be overcome by chromatoscopy and radiological methods. Interoperatively challenges arise due to anatomical factors like narrow lumen and peristalsis and technical issues such as fibrosis, limited subcausal space, bleeding, disorientation and prolonged procedure time. Deep anesthesia and multi-tunneling techniques can help overcome these. Postoperatively risks like lesion retrieval, bleeding, perforation or structure may remain. This can be managed with suturing techniques. 51-year-old female patient presented with iron deficiency anemia and diarrhea. A large LSDG of 15 cm in size was noted in rectosigmoid angle. Previous mucosal biopsies revealed adenoma. EUS and MRI staging concluded local disease and EST was decided. The objective is to provide emboloc removal without any organ or function loss with endoscopic closure that will enable fast and secure recovery. During the colonoscopy, a circumferential flat and granular lesion was observed in rectum 4 cm from anal verge extending approximately for approximately 15 cm to rectosigmoid junction. Under the TXI, MBI and optical magnification, the vascular and surface pattern appeared regular. Under general anesthesia, the following strategy was planned. Using a standard gastroscope, two white tunnels would be created, starting from the anal side and advancing proximally. The tunnels would then be merged, taking gravity into account for proper orientation. The resection area was to be closed using the following technique. A prolonged suture would be passed through the proximal halter area, middle of the resection site and distal halter area as full thickness, muscular and full thickness insertions respectively. Suturing would continue until the proximal and distal resection areas were fully closed. Closure was planned with the three sutures to prevent dead space. The procedure began with submucosal injection, followed by mucosal incision and submucosal dissection using a dual knife allowing entry into the submucosal space. A tunnel was created in proximal direction. When a bluish mucosal color change was observed, a proximal mucosal incision was made completing the first tunnel. Tunneling technique allowed the submucosal space to expand more easily with minimal submucosal injection, providing effective elevation. During this process, a TT knife known for its superior injection capabilities was utilized to facilitate continued tunneling. The tunneling technique was used to facilitate continued tunneling. This tunnel was both long and wide and no adverse events occurred. The technique minimized the risk of the accidental muscle damage by keeping the knife parallel to muscle layer. Additionally, the impact of the respiration and peristalsis on dissection was reduced. Using the same strategy, a second tunnel was created. The tunneling technique helped maintain orientation, prevented dissected areas from collapsing into the lumen, and improved visibility of the dissection field. The two tunnels were then merged with gravity orientation guiding the process. Positioning adjustments were made as necessary during the merging process. The merge was successfully completed using the same approach. Other advantages of this technique included the isolation of major vascular structures, allowing effective coagulation of larger vessels rather than smaller ones, reducing the risk of bleeding and enabling cleaner dissection. At the final stage, the patient was repositioned and the remaining area was dissected using the same strategy. Upon completion, the circumferential resection area was clearly visible with no sign of the perforation or muscle damage. To prevent structure and delay adverse events, the resection area was closed using the over-stitch system with a dual-channel scope. Proline sutures were pastoral to proximal healthy side, muscularis propria in the middle, and distal healthy side. Closure was then achieved with the three sutures and three cinches, fully sealing the resection area. The resulting endoscopic anastomosis allowed easy passage to proximal area using a standard dual-channel scope. The lesion was removed circumferentially in an en bloc patient using sponge forceps. The lesion long axis measured approximately 33 centimeter. The procedure lasted 257 minutes. Remarkably no cancer was found. Pathology confirmed a high-grade tuberculosis adenoma with clear margins. 84 months endoscopic follow-up. Healing was progressing well and no stricture was observed. Follow-up. No periprocedural adverse events was faced. She discharged on post-operative day 3 and two-year colonoscopic follow-up revealed neither stricture nor recurrence. Using multi-tunneling technique the lesion is pushed toward the lumen. Submucosa is easily exposed. Effective submucosal elevation is achieved without frequent injections. The knife stays parallel to muscle layer minimizing the risk of the muscle injury. Large vascular structure are isolated so bleeding risk is reduced. And the defined strategy prevents disorientation and time loose ensuring efficient dissection. The result in unblocked resection and faster dissection. Large circumferential defect if left unclosed can lead to delayed bleeding, perforation, prolonged healing and strictures. Closing the defect may reduce fibrosis and stricture risk by lowering myofibroblast activity. It can also decrease the risk of the delayed adverse events and promote faster healing. EST is an effective treatment method for large lesions. The tunneling technique is one of the effective method that facilitates removal of large lesions. Closing the resection site may reduce risk early and long-term adverse events and decrease recovery time.

endoscopic subcausal dissection

colorectal tumor

multi-tunneling techniques

minimally invasive surgery

postoperative recovery