Safety of endoscopic procedures with monopolar versus bipolar instruments in an ex vivo porcine model

Abstract

Background: Monopolar instruments are generally used in colorectal endoscopic mucosal resection (EMR). Bipolar instruments have previously been reported to be as safe as monopolar instruments. We sought to compare the safety of the monopolar and bipolar snare and hemostatic forceps in an animal model.

Methods: We created 5-mm, 10-mm, and 15-mm target lesions on an ex vivo porcine rectum. Two lesions of each size were resected via monopolar polypectomy (M-P), monopolar EMR (M-E), bipolar polypectomy (B-P), and bipolar EMR (B-E). We performed a pathological evaluation of the conditions of perforation and the effects of burning on the tissues. In addition, we burned the muscularis propria covered with submucosal layer using monopolar and bipolar hemostatic forceps and performed pathological evaluations.

Results: Polypectomy and EMR were performed in a total of 24 target lesions. A perforation was found on histology in one case of M-P and one case of M-E after removing target lesions of 15 mm in diameter. There were no perforations during endoscopic resection using the bipolar snare. The thermal denaturation in B-P did not reach the muscularis propria layer regardless of the size of the target lesion. Although thermal damage after using monopolar hemostatic forceps was extensive, thermal denaturation was only seen on the surface of the submucosal layer when bipolar hemostatic forceps were used.

Conclusions: Bipolar instruments cause less damage to the tissue than monopolar instruments. Our results also suggest that bipolar instruments may be safer than monopolar instruments in endoscopic procedures for colorectal lesions.

Keywords: Bipolar instrument; Colorectal endoscopic resection; Monopolar instrument.

Fig. 1

Histopathology (H-E stain) of the target lesion. (a) Distance is from the muscularis propria to the thermal denaturation of the submucosal layer. (b) Area shows tissue damage to the muscularis propria. Dist, distance

Fig. 2

Histopathology (H-E stain) of the target lesion with a diameter of 15 mm removed with a monopolar snare. (a) Histopathology after polypectomy using a monopolar snare. (b) Histopathology after EMR using a monopolar snare. Both A and B show cases with perforation

Fig. 3

Histopathology (H-E stain) of the 15-mm target lesion removed with a bipolar snare. (a) Histopathology after polypectomy using a bipolar snare. (b) Histopathology after EMR using a bipolar snare

Fig. 4

Exposed muscularis propria burned by monopolar hemostatic forceps or bipolar hemostatic forceps. (a) The three burning points of the upper row were made using bipolar forceps, and the thee burning points of the lower row were made using monopolar forceps. (b) Histopathology of the burning point using monopolar hemostatic forceps (15 s). (c) Histopathology of the burning point using bipolar hemostatic forceps (15 s)