Large non-pedunculated colorectal polyps (LNPCP) and laterally spreading tumours (LST) >10mm involving the appendix orifice (AO) are notoriously challenging to treat with endoscopic resection (ER). Few studies report outcomes of conventional ER to treat these lesions. The optimal therapy and expected outcomes remain unclear. We report the outcome after EMR and ESD of lesions involving the AO from a large series of ER performed at a tertiary referral centre. 

Patients undergoing ER at a tertiary referral centre between January 2011 and September 2023 were included. Techniques and outcomes of ER of lesions involving the AO were compared with other colorectal locations.  Involvement of the AO was defined as any LNPCP or LST encroaching within 5mm of the orifice. These were classified as encroaching the AO, involving part of the circumference of the AO and involving the full circumference of the AO. 

ER was performed for 1596 LNPCP and LSTs during the study period. 40 lesions involved the AO: 10 encroached within 5mm of the AO, 14 involved part of the circumference and 16 involved the full circumference. 25 (63%) were resected by EMR, 8 by ESD (20%) and 7 by Hybrid ESD (18%). Initial successful ER was similar for lesions involving the AO and other colonic LNPCP (95.0% versus 97.6%, p=0.27). Clinically significant perforation occurred in 3 patients with lesions involving the AO (2 with partial circumference involvement and 1 with complete circumference involvement) and was more frequent after ER of these lesions than others (7.5% versus 1.2%, p<0.001). 2 of these patients required surgery. The incidence of post procedure bleeding was similar (p=0.44). One patient developed appendicitis, more than 12 months after resection. Recurrent/residual adenoma at first surveillance was significantly more likely after ER of AO lesions than others (22.2% versus 4.8%, p<0.001). Significantly more patients with lesions involving the AO ultimately required surgery for any reason than patient with other colorectal lesions (12.5% versus 3.9%, p=0.02). This was significantly more likely for AO lesions involving the complete or partial circumference (18.8% versus 14.3% partial circumference involvement versus 0% encroaching AO versus 3.9% other locations, p=0.004). 

These results demonstrate the challenging nature of ER for lesions involving the AO. Safe and effective ER without recurrence is achieved for many patients, including those with lesions involving the complete circumference, but significant complications, recurrence and surgery are more common with these lesions. Given there are relatively low risk minimal access surgical options to treat these lesions, these data will help inform detailed discussions with patients regarding the risks and benefits of ER (which differ from LNPCP elsewhere in the colon).