Abstract
Background and study aims Curability of colorectal tumors is associated with resection depth and layer in endoscopic
resection. Underwater endoscopic mucosal resection (UEMR) has not undergone sufficient
histopathological evaluation. We conducted a pilot study to compare the effectiveness,
including resection depth and layer, of UEMR and conventional endoscopic mucosal resection
(CEMR).
Patients and methods This study was a single-center, retrospective study. Patients with colorectal lesions
were treated by UEMR or CEMR between January 2018 and March 2020. Eligible patients
were selected from included patients in a 1:1 ratio using propensity score matching.
We compared the resection depth and layer and treatment results between the UEMR and
CEMR groups.
Results We evaluated 55 patients undergoing UEMR and 291 patients undergoing CEMR. Using
propensity score matching, we analyzed 54 lesions in each group. The proportion of
specimens containing submucosal tissue was 100 % in both groups. The median thickness
of the submucosal tissue was significantly greater in the CEMR group than in the UEMR
group [1235 µm (95 % confidence interval [CI], 1020–1530 µm) vs. 950 µm (95 % CI,
830–1090 µm), respectively]. However, vertical margins were negative in all lesions
in both groups.
Conclusions Our findings suggest that the median thickness of submucosal tissue in the UEMR group
was about 1,000 μm. Even though the resection depth achieved with UEMR was more superficial
than that achieved with CEMR, UEMR may be a treatment option, especially for colorectal
lesions ≤ 20 mm in diameter without suspicious findings of submucosal deeply invasive
cancer.
