Geometry of cold snare polypectomy and risk of incomplete resection

Abstract

Background and Aims Cold snare polypectomy (CSP) is safer and equi-efficacious to hot snare polypectomy (HSP) for the removal of small (<10mm) colorectal polyps. The upper limit of polyp size that can be effectively managed by piecemeal CSP (p-CSP) without an excessive burden of recurrence is unknown. Methods Resection error rate (RER) for CSP and HSP were calculated based on the rate of incomplete resection in the literature. Polyp area, snare size, estimated number of resections and optimal resection defect area were modelled. The rate of incomplete resection (RIR) is defined as RIR=1-(1-p)n, where p is the RER and n the number of resections. Results Polyp area increases quadratically as polyp radius increases. Comparing a 20mm vs 40mm polyp, area is four times greater (314.16mm2 vs 1256.64mm2) and the number of required resections was 3 times greater (11 vs 33, assuming 8 mm piecemeal resection pieces for p-CSP respectively). The RIR of a 40mm polyp by HSP and p-CSP were 15.1%-23% and 40.74%-60.6% respectively. Conclusion RER is more important with p-CSP than with HSP. RER and consequent RIR increases with increasing polyp size. Given the overwhelming safety of CSP, specific techniques to minimise the RER should be studied and developed.