Gastroenterol Res

Gastroenterology Research, ISSN 1918-2805 print, 1918-2813 online, Open Access

Article copyright, the authors; Journal compilation copyright, Gastroenterol Res and Elmer Press Inc

Journal website http://www.gastrores.org

Original Article

Volume 11, Number 4, August 2018, pages 274-279

Feasibility of Underwater Endoscopic Mucosal Resection for Colorectal Lesions: A Single Center Study in Japan

Figure 1. Procedure for underwater endoscopic mucosal resection (U-EMR). (A, B) A sessile lesion about 30 mm located in the ascending colon. (C) The lumen at the site of the lesion was filled with water, using the water-jet system, and the lesion was floated in the lumen. (D) The lesion was snared, using a 33-mm snare, and the lesion was tightened-up. (E) The mucosal defect after U-EMR was usually smaller than after conventional EMR. (F) Resected specimen after successful en bloc resection.

Figure 2. A case of perforation. (A) A laterally spreading, granular type lesion about 30 mm located in the ascending colon. (B) Adequate floating of the lesion could not be achieved and, therefore, submucosal injection, using normal saline, was performed before snaring. (C) The lesion was snared, using a 33-mm snare, and the lesion was tightened-up. (D) En bloc resection was achieved but the muscularis propria was slightly injured at the center of the mucosal defect. (E) An obvious perforation was identified after gas insufflation in the lumen. (F) Endoscopic clipping was performed, and surgical intervention was not required.

**Table 1.** Patient and Lesion Characteristics
Number of cases	64 lesions in 38 cases
Mean age, years (range)	68.6 (25 - 90)
Male sex, N (%)	26 (68)
Mean size of lesions, mm (range)	16.2 (6 - 40)
< 10 mm, N (%)	8 (13)
10 - 19 mm, N (%)	34 (53)
20 - 29 mm, N (%)	15 (23)
≥ 30 mm, N (%)	7 (11)
Location
Cecum, N (%)	9 (14)
Ascending colon, N (%)	12 (19)
Transverse colon, N (%)	12 (19)
Descending colon, N (%)	7 (11)
Sigmoid colon, N (%)	17 (27)
Rectum, N (%)	7 (11)
Morphology
0-Is, N (%)	33 (52)
0-Ip, N (%)	10 (16)
0-IIa, N (%)	18 (28)
0-IIa+Is, N (%)	3 (5)
Histology
Low-grade adenoma, N (%)	31 (48)
High-grade adenoma, N (%)	8 (13)
Mucosal cancer, N (%)	11 (17)
Submucosal cancer, N (%)	4 (6)
Sessile serrated adenoma/polyp, N (%)	4 (6)
Traditional serrated adenoma, N (%)	1 (2)
Hyperplastic polyp, N (%)	3 (5)
Inflammatory polyp, N (%)	2 (3)

Table 1. Patient and Lesion Characteristics

Number of cases

64 lesions in 38 cases

Mean age, years (range)

68.6 (25 - 90)

Male sex, N (%)

26 (68)

Mean size of lesions, mm (range)

16.2 (6 - 40)

< 10 mm, N (%)

8 (13)

10 - 19 mm, N (%)

34 (53)

20 - 29 mm, N (%)

15 (23)

≥ 30 mm, N (%)

7 (11)

Location

Cecum, N (%)

9 (14)

Ascending colon, N (%)

12 (19)

Transverse colon, N (%)

12 (19)

Descending colon, N (%)

7 (11)

Sigmoid colon, N (%)

17 (27)

Rectum, N (%)

7 (11)

Morphology

0-Is, N (%)

33 (52)

0-Ip, N (%)

10 (16)

0-IIa, N (%)

18 (28)

0-IIa+Is, N (%)

3 (5)

Histology

Low-grade adenoma, N (%)

31 (48)

High-grade adenoma, N (%)

8 (13)

Mucosal cancer, N (%)

11 (17)

Submucosal cancer, N (%)

4 (6)

Sessile serrated adenoma/polyp, N (%)

4 (6)

Traditional serrated adenoma, N (%)

1 (2)

Hyperplastic polyp, N (%)

3 (5)

Inflammatory polyp, N (%)

2 (3)

**Table 2.** Study Outcomes
‡Complete resection rate was defined by a negative pathological margin of resected specimen that was obtained by successful en bloc resection.
En bloc resection rate
Overall, %	81 (52/64 lesions)
< 10 mm, %	100 (8/8)
10 - 19 mm, %	94 (32/34)
20 - 29 mm, %	53 (8/15)
≥ 30 mm, %	57 (4/7)
Complete resection rate‡
Overall, %	54 (32 of 59 neoplastic epithelial lesions)
< 10 mm, %	88 (7/8)
10 - 19 mm, %	63 (20/32)
20 - 29 mm, %	25 (3/12)
≥ 30 mm, %	29 (2/7)
Post procedural bleeding, N (%)	3 (5)
Perforation, N (%)	1 (2)

Table 2. Study Outcomes

‡Complete resection rate was defined by a negative pathological margin of resected specimen that was obtained by successful en bloc resection.

En bloc resection rate

Overall, %

81 (52/64 lesions)

< 10 mm, %

100 (8/8)

10 - 19 mm, %

94 (32/34)

20 - 29 mm, %

53 (8/15)

≥ 30 mm, %

57 (4/7)

Complete resection rate‡

Overall, %

54 (32 of 59 neoplastic epithelial lesions)

< 10 mm, %

88 (7/8)

10 - 19 mm, %

63 (20/32)

20 - 29 mm, %

25 (3/12)

≥ 30 mm, %

29 (2/7)

Post procedural bleeding, N (%)

3 (5)

Perforation, N (%)

1 (2)

**Table 3.** Cases of Submucosal Cancer in This Study
LST-NG: laterally spreading tumor, non-granular type; LST-G: laterally spreading tumor, granular type; N/A: not applicable.
Age (years)	67	71	90	85
Sex	F	M	M	M
Location	Ascending colon	Ascending colon	Sigmoid colon	Cecum
Size (mm)	40	30	12	15
Morphology	0-IIa+Is (LST-G)	0-Is	0-IIa (LST-NG)	0-Is
En bloc resection	No	No	Yes	Yes
Submucosal invasion depth (µm)	2,500	2,800	2,000	150
Lateral margin	N/A	N/A	+	-
Base margin	-	-	-	-

Table 3. Cases of Submucosal Cancer in This Study

LST-NG: laterally spreading tumor, non-granular type; LST-G: laterally spreading tumor, granular type; N/A: not applicable.

Age (years)

Sex

Location

Ascending colon

Sigmoid colon

Cecum

Size (mm)

Morphology

0-IIa+Is (LST-G)

0-Is

0-IIa (LST-NG)

0-Is

En bloc resection

Yes

Submucosal invasion depth (µm)

2,500

2,800

2,000

150

Lateral margin

N/A

Base margin