Peacemule-Kolzner resection is an increasingly popular endoscopic resection technique for large non-pedunculated colorectal polyps. Especially for serrated lesions, which tends to be more superficial, Peacemule-Kolzner resection can be an effective resection technique. Although higher recurrence rates have been reported compared to conventional EMR for large adenomas, Kolzner resection offers the advantage of mitigating periprocedural adverse events with excellent safety profile. In recent meta-analysis and randomized controlled trials comparing Peacemule-Kolzner resection and conventional EMR, overall adverse event rate was 1% with Kolzner resection. With respect to perforation, this is exceptionally rare and no perforation was reported in the recent randomized controlled trials. Here, we present the video case of intraprocedural identification and management of perforation during Peacemule-Kolzner resection for a large CES-L serrated lesion. A 63-year-old female with quiescent colonic Crohn's disease underwent colonoscopy for dysplasia surveillance, during which multiple pairs 2A polyps with optical features consistent with serrated class lesions were identified. The procedure was carried out under endoscopy-directed conscious sedation using midazolam and fentanyl. At proximal transverse colon, a CES-L pairs 2A polyp was seen. Optical features were consistent with serrated class lesion. Mucus cap was seen on high-definition white light imaging. Blue light imaging showed lighter surface pattern with sparse, lacy vascular pattern. Peacemule-Kolzner resection was performed for the serrated CES-L polyp. We used methylene blue with diluted epinephrine 1 to 100,000 as lifting agent and performed Peacemule-Kolzner resection using 10-millimeter dedicated cold polypectomy snare. There was no evidence of inflammatory bowel disease activity within surrounding mucosa, but some cell mucosal fibrosis was identified during the resection. After completing Peacemule-Kolzner resection of the first lesion, we could then visualize an adjacent large 40-millimeter pairs 2A CES-L polyp with similar serrated optical features. We proceeded to performing Peacemule-Kolzner resection of this lesion as well. During the process of Kolzner resection of the distal lesion nearby the defect of previous lesion, we could visualize a glimpse of fat-laden connective tissue at the previous Kolzner resection defect site as shown here. On close inspection of the evolving resection defect site, we could see fat-laden connective tissue within a defect of muscular ispropria. To better assess for deep mural injury, we used topical submucosal chromoendoscopy using methylene blue solution and confirmed no uptake of methylene blue dye, suggesting muscular ispropria defect. This was consistent with Sydney DMI classification type 4 with visualization of intraprednial fat. We performed selective closure of the defect using five 3D-scope mechanical clips with good apposition of the defect margins. Once closure is achieved, we continued on with completing the endoscopic resection while carefully monitoring the patient for any signs of discomfort. In summary, the patient had multiple Paris 2A polyps which were removed by Kolzner resection, including a large 40mm transverse colonic polyp as shown here, with type 4 DMI injury or perforation which was closed successfully with 3D-scope clips. The patient was observed post-procedure for one hour and received intravenous antibiotics. As the patient was asymptomatic, no radiographic imaging was performed, and the patient was discharged with a five-day course of antibiotics. At one week follow-up, the patient remained well without any delayed adverse events. Histopathology confirmed a CES-acerated lesion without dysplasia. Perforation is the most feared endoscopic adverse event. Recently, Kolzner resection has gained traction for large non-pedunculated colorectal polyps due to its lower adverse event rate compared to conventional EMR. The perforation rarely reported in the literature, reinforcing the belief that Kolzner resection protects the endoscopist from causing DMI. Our case highlights that perforation can still occur with Kolzner resection even without the use of electrocautery. Recognition of DMI is particularly challenging as Sydney DMI classification such as the target sign is facilitated by electrocautery-accentuating muscular dyspropria injury, which is absent during Kolzner resection. Potential optical cues include visualization of uninjured muscular dyspropria and intraperitoneal fat as demonstrated in our case. Perforation management is predicated on a protocolized approach to achieve successful defect closure. Some helpful tips for effective perforation management includes the following. It is imperative for defect closure technologies to be readily available in the endoscopy unit along with having a team competent in their use. Carbon dioxide should be used universally for large polyp resection management as it minimizes the risk of tension pneumoperitoneum, thus enabling the endoscopist to perform defect closure in a controlled environment. If deep neural injury is identified, the patient should be positioned, if not already, to manipulate the fluid pool to the contralateral wall, thus minimizing peritoneal contamination. If uncertain about deep neural injury, topical submucosachroma endoscopy is a proven adjunct to facilitate Sydney DMI classification. Tissue resection-related perforations, specifically when managed through the scope clips, need only address the area of concerns, as closure of the entire defect may risk incomplete deep neural injury management. Piecemeal cold-snare resection is an effective and safe resection technique for large non-pedunculated colorectal polyps. Though rare, serious adverse events including perforation can still occur. Therefore, it is important for the endoscopist to still remain vigilant and assess defect sites closely even after cold-snare resection to ensure no deeper injury has occurred to avoid more serious complication. In increasing utilization of cold-snare resection, universal evaluation of post-resection defect using the Sydney DMI classification should be considered standard of care, with an appreciation for classification modification when using resection modalities other than EMR.

Peacemule-Kolzner resection

colorectal polyps

serrated lesions

perforation management

post-resection evaluations