Heat sink effect of underwater polypectomy in a porcine colon model

Chih-Wei Tseng,Chung-Chih Lin,Felix W Leung,Yu-Hsi Hsieh,Malcolm Koo

doi:10.1186/s12876-021-01985-1

Abstract

BackgroundUnderwater polypectomy without the need for submucosal injection has been reported. A heat-sink effect by immersing the polyp in water was proposed but no such experiment has been performed to support the claim. We compared the temperature rise on the serosal side during polypectomy between air- and water-filled colon.MethodFreshly harvested porcine colons were placed in a metal tray with cautery electrode pad attached to its bottom. An upper endoscope was used with a cap and a rubber band mounted to the distal end. A mucosal site was randomly selected and identified on its serosal surface with a marker while suction was applied. Suction was applied again and a ligation band was applied to create a polyp. A cautery snare grasped the artificial polyp just below the band. An assistant placed the tip of a thermometer at the marked site on the serosal surface to record the baseline temperature before cautery and the highest temperature during polypectomy. Seven polypectomies in air and underwater were performed.ResultsMean (standard deviation) baseline temperature were 23.3 (0.6) °C and 23.4 (0.6) °C in the air and water groups, respectively. The maximum rise in temperature during polypectomy was 6.1 (4.5) °C and 1.4 (1.0) °C in the air and water groups, respectively (P = 0.004).ConclusionsThe maximum temperature rise during polypectomy was significantly less when polypectomy was performed underwater, supporting the hypothesis that a heat-sink effect does exist during underwater polypectomy.

Highlights

Endoscopic resection of colon polyps is estimated to prevent around 80% of colorectal cancers [1, 2]
The maximum temperature rise during polypectomy was significantly less when polypectomy was performed underwater, supporting the hypothesis that a heat-sink effect does exist during underwater polypectomy
As observed with endoscopic sonography, the colonic folds consisted of involutions of the mucosa and submucosa “float up” in water, while the muscularis propria remains circular and does not follow the involutions, so the muscularis propria would unlikely be captured by the snare underwater [8]

Summary

Introduction

Endoscopic resection of colon polyps is estimated to prevent around 80% of colorectal cancers [1, 2]. As observed with endoscopic sonography, the colonic folds consisted of involutions of the mucosa and submucosa “float up” in water, while the muscularis propria remains circular and does not follow the involutions, so the muscularis propria would unlikely be captured by the snare underwater [8]. Another possible mechanism is the heat-sink effect of water that offers protection against deeper thermal injury during UWP. Our hypothesis is that the temperature rise would be significantly less during UWP compared with polypectomy in an air-filled colon because of a heat-sink effect. We compared the temperature rise on the serosal side during polypectomy between air- and water-filled colon

Methods

Results

Discussion

Conclusion