From the AGA Journals

Underwater endoscopic mucosal resection may be an option for colorectal lesions



For intermediate-size colorectal lesions, underwater endoscopic mucosal resection (UEMR) may offer cleaner margins than conventional EMR without increasing procedure time or risk of adverse events, based on a recent head-to-head trial conducted in Japan.

UEMR was associated with higher R0 and en bloc resection rates than was conventional EMR (CEMR) when used for intermediate-size colorectal lesions, reported lead author Takeshi Yamashina, MD, of Osaka (Japan) International Cancer Institute, and colleagues. The study was the first multicenter, randomized trial to demonstrate the superiority of UEMR over CEMR, they noted.

Although CEMR is a well-established method of removing sessile colorectal lesions, those larger than 10 mm can be difficult to resect en bloc, which contributes to a local recurrence rate exceeding 15% when alternative, piecemeal resection is performed, the investigators explained in Gastroenterology

Recently, UEMR has emerged as “an alternative to CEMR and is reported to be effective for removing flat or large colorectal polyps,” the investigators wrote. “With UEMR, the bowel lumen is filled with water instead of air/CO2, and the lesion is captured and resected with a snare without submucosal injection of normal saline.”

To find out if UEMR offers better results than CEMR, the investigators recruited 211 patients with 214 colorectal lesions at five centers in Japan. Patients were aged at least 20 years and had mucosal lesions of 10-20 mm in diameter. Based on macroscopic appearance, pit pattern classification with magnifying chromoendoscopy, or narrow-band imaging, lesions were classified as adenoma, sessile serrated adenoma/polyp, or intramucosal adenocarcinoma. Patients were randomly assigned in a 1:1 ratio to the UEMR or CEMR group, and just prior to the procedure, operators were informed of the allocated treatment. Ten expert operators were involved, each with at least 10 years of experience, in addition to 18 nonexpert operators with less than 10 years of experience. The primary endpoint was the difference in R0 resection rate between the two groups, with R0 defined as en bloc resection with histologically negative margins. Secondary endpoints were en bloc resection rate, adverse events, and procedure time.

The results showed a clear win for UEMR, with an R0 rate of 69%, compared with 50% for CEMR (P = .011), and an en bloc resection rate that followed the same trend (89% vs. 75%; P = .007). Neither median procedure times nor number of adverse events were significantly different between groups.

Subset analysis showed that UEMR was best suited for lesions at least 15 mm in diameter, although the investigators pointed out the superior R0 resection rate with UEMR held steady regardless of lesion morphology, size, location, or operator experience level.

The investigators suggested that the findings give reason to amend some existing recommendations. “Although the European Society of Gastrointestinal Endoscopy Clinical Guidelines suggest hot-snare polypectomy with submucosal injection for removing sessile polyps 10-19 mm in size, we found that UEMR was more effective than CEMR, in terms of better R0 and en bloc resection rates,” they wrote. “Hence, we think that UEMR will become an alternative to CEMR. It could fill the gap for removing polyps 9 mm [or larger] (indication for removal by cold-snare polypectomy) and [smaller than] 20 mm (indication for ESD removal).”

During the discussion, the investigators explained that UEMR achieves better outcomes primarily by improving access to lesions. Water immersion causes lesions to float upright into the lumen, while keeping the muscularis propria circular behind the submucosa, which allows for easier snaring and decreases risk of perforation. Furthermore, the investigators noted, water immersion limits flexure angulation, luminal distension, and loop formation, all of which improve maneuverability and visibility.

Still, UEMR may take some operator adjustment, the investigators added, going on to provide some pointers. “In practice, we think it is important to fill the entire lumen only with fluid, so we always deflate the lumen completely and then fill it with fluid,” they wrote. “[When the lumen is filled], it is not necessary to change the patient’s position during the UEMR procedure.”

“Also, in cases with unclear endoscopic vision, endoscopists are familiar with air insufflation but, during UEMR, it is better to infuse the fluid to expand the lumen and maintain a good endoscopic view. Therefore, for the beginner, we recommend that the air insufflation button of the endoscopy machine be switched off.”

Additional tips included using saline instead of distilled water, and employing thin, soft snares.

The investigators reported no external funding or conflicts of interest.

SOURCE: Yamashina T et al. Gastro. 2018 Apr 11. doi: 10.1053/j.gastro.2019.04.005.

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