Mechanism behind reduced resection ability of bent snares during cold snare polypectomy

Accidental bending of the snare sheath occasionally occurs during cold snare polypectomy (CSP). We aimed to demonstrate whether snare bending reduces resection ability and, if it does, what causes this reduction. Using currently available CSP snares and prototype snares, we investigated changes in the resection ability of bent snares as well as the stiffness of their sheaths and wire spindles. Furthermore, to evaluate the performance of the bent snares, we measured the completion rate of CSP for 5-mm-diameter pseudo-lesions on the porcine rectal mucosa. Snare bending significantly decreased resection ability and wire spindle stiffness. Compared with bending the snares once, bending the snares five times further decreased the resection ability and wire spindle stiffness. A strong correlation was observed between wire spindle stiffness and resection ability after snare bending (correlation coefficient = 0.82; P < 0.001). Additionally, snare bending reduced the completion rate of CSP. Bending a CSP snare causes decreased wire spindle stiffness, thereby reducing its resection ability and potentially lowering the resection completion rate. The resection ability cannot be restored; therefore, snare replacement is recommended.