Histopathologic studies of colorectal postendoscopic resection sites: "skipping electrothermal injury" associated with endoscopic resection procedures.

To elucidate the pathologic changes due to endoscopic resection (ER), 32 post-ER sites in 24 surgically removed colorectal specimens and the previous ER specimens were examined. The depth of all the previous ER specimens was restricted to the submucosa, and all post-ER sites showed submucosal stromal changes of various degrees. Fourteen sites (43.8%) showed muscular or serosal changes. One of these lesions was considered to be a reaction to a tattoo agent, but all the other lesions were considered to represent skipping electrothermal injury caused by electrical current passing through the colorectal wall. The lesions consisted of muscular depletion in the inner layer of the muscularis propria (12 sites, 37.5%), hemorrhage or fibrosis between the inner and outer layers of the muscularis propria (3 sites, 9.4%), and serosal changes (10 sites, 31.3%). These skip regions would be vulnerable to electrical current. These findings suggest that asymptomatic electrothermal injury associated with ER is frequent. Statistically, the electrothermal injury appeared to be related to the size of the previous ER specimens. However. these results also reveal that the ER of tissues <10 mm can cause electrothermal injury and can result in full-thickness necrosis.