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Suwa et al. Mini-invasive Surg 2022;6:20 https://dx.doi.org/10.20517/2574-1225.2021.123 Page 7 of 11

colorectal polyps. However, no studies have directly compared the two treatments, and RCTs comparing the
two are needed to determine the indications.

UEMR for SNADETs in our institution
In our center, UEMR for SNADETs is indicated for adenomas larger than 10 mm and for intramucosal
carcinomas no larger than 30 mm in size that are diagnosed endoscopically. The typical case treated with
UEMR is an adenocarcinoma that is 0-IIa in the Paris classification, with a size of 12 mm and located in the
3rd portion. An example of this type of case is presented in Figure 2.

Between January 2015 and July 2021 at the Shizuoka Cancer Center, 76 lesions in 71 patients [male/female:
41/30; median age: 70.5 years (range, 28-89 years)] were resected by UEMR. Overall, 12 lesions were in the
bulbs, 61 were in the 2nd portion, and 3 were in the 3rd portion. The median size of the lesions was 10 mm
(range, 2-40 mm). Moreover, 10 lesions were the macroscopic type 0-I in the Paris classification system, 37
were 0-IIa, 21 were 0-IIa+IIc, and 8 were 0-IIc. A preoperative biopsy was performed before UEMR in 37
lesions (48.7%).

All lesions that underwent UEMR were resected without conversion to any other techniques, such as ESD
(the UEMR completion rate was 100%). The median procedure time (from the completion of water
immersion to the end of resection) was 5 min (range, 1-104 min), and the en bloc resection rate was 82.9%
(63/76). Compared with CSP, the en bloc resection rate of UEMR was lower, but this may be due to the
invisibility of the anal side of the lesion during snaring, which could cause snare slipping. En bloc resection
is ideal for an accurate pathological diagnosis; therefore, some innovations in the procedure or device are
expected to solve this problem.

The percentage of spurting bleeding immediately after UEMR was 0%. Moreover, prophylactic clipping
after UEMR was performed in 72 lesions (94.7%), and no intraoperative adverse events were observed.
Delayed bleeding occurred in two lesions (2.6%), and no delayed perforation occurred. In both cases of
delayed bleeding, the UEMR procedure was completed without prophylactic clipping, and emergency
endoscopy was performed within 24 h following hematemesis. Fortunately, endoscopic hemostasis was
achieved, and surgical intervention was not required. In general, resection with electrocautery is expected to
suppress tumor remnants due to the “burn effect”; however, the risk of delayed bleeding increases due to
microvascular damage. We believe that prophylactic clipping is an essential procedure after UEMR because
of the burn effect and the larger mucosal defect in UEMR as compared with the defect in CSP, which
increases the risk of postoperative complications. In addition, a previous report on colorectal polyps
suggests that bipolar devices have the potential to reduce perioperative complications compared with
monopolar devices, but this has not been reported in the duodenum .
[25]

The median size of the resected specimens was 9 mm (range, 3-40 mm). Histopathological evaluations
revealed 55 adenomas, 17 adenocarcinomas (intramucosal), and 4 nonneoplastic lesions. Of the 72
neoplastic lesions (adenomas and adenocarcinomas), the HM was negative in 36, positive in 1, and
indeterminate in 35; for the VM, 70 were negative, 1 was positive, and 2 were indeterminate. The R0
resection rate (en bloc resection with negative margins) was 52.0%. Similar to CSP, the R0 resection rate was
relatively low. This might be due to an inadequate histopathological assessment of the specimen’s edges
because the lesion is relatively small. For procedures such as UEMR and CSP, which included relatively
small lesions, the R0 resection rate is an inappropriate measure for assessing the curability of endoscopic
treatment, and a careful assessment of the residual recurrence rate, including the associated factors, is
important.