Suitability of Endoscopic Full Thickness Resection for Appendiceal Orifice Polyps

A 67-year-old woman underwent colonoscopic endoscopic full-thickness resection (EFTR) for a 10 mm sessile serrated lesion at the appendiceal orifice (AO) (Figure 1). The lesion had been identified during surveillance colonoscopy for prior serrated polyps. An over-the-scope clip (OTSC) was used for resection. The procedure was reportedly uneventful and the patient was discharged the same day. Three days later, she developed severe right lower quadrant pain with raised inflammatory markers (CRP > 350 mg/L). CT demonstrated a distended appendix with surrounding inflammation and reactive ileus, consistent with post-EFTR appendicitis (Figure 2). No free gas was evident, but a microperforation could not be excluded. The patient was treated with intravenous antibiotics and recovered following a short inpatient stay. Two years later, she re-presented with recurrent right lower quadrant pain and a rim-enhancing mass adjacent to the caecum (Figure 3). CT imaging showed the OTSC no longer in situ and a lobulated peri-caecal collection abutting the sigmoid colon. At elective laparotomy, a dilated appendix adherent to the sigmoid colon was found with mucinous contents and a walled-off collection. Retrograde appendicectomy and partial sigmoid resection were performed. Histology demonstrated a low-grade appendiceal mucinous neoplasm (LAMN) with acellular mucin at the serosal surface and within the intra-abdominal collection, suggestive of mucin spillage into the peritoneal cavity. This sequence of events is consistent with appendiceal obstruction following OTSC placement at the AO. Occlusion of the appendiceal lumen likely prevented drainage, resulting in progressive distension, raised intraluminal pressure and secondary inflammation, culminating in mucocoele formation and microperforation- a mechanism analogous to appendicitis secondary to an obstructing appendicolith. A direct causal relationship between EFTR and the subsequent diagnosis of LAMN is unlikely. However, it is plausible that the LAMN was present prior to the initial procedure. In this context, appendiceal obstruction and inflammation may have contributed to perforation or mucin spillage, thereby amplifying the clinical consequences of an otherwise occult neoplasm. Recent series have reported appendicitis rates of 14%–17% following EFTR at the AO, with over half requiring surgery despite peri-procedural antibiotics [1-5]. Although EFTR offers a minimally invasive option for complete histological resection of colonic lesions, its use for AO polyps is controversial. Other endoscopic techniques such as endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD), or hybrid approaches such as combined endoscopic–laparoscopic surgery (CELS), can be challenging and risky in this area [1, 5, 6]. Partial caecectomy may be more appropriate than endoscopic options in certain cases. A patient centred multidisciplinary approach involving the patient, gastroenterologists and surgeons should be utilised in decision-making. Patients selected for an endoscopic approach should be counselled and closely monitored for early and late complications. Open access publishing facilitated by The University of Auckland, as part of the Wiley - The University of Auckland agreement via the Council of Australasian University Librarians. The authors have nothing to report. The authors have no disclosures to make. Patient consent for clinical information and imaging has been obtained for the publication of this article. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.