High complete resection rates of underwater endoscopic mucosal resection for intermediate-sized sessile serrated lesions.

Objective: Sessile serrated lesions (SSLs) pose a risk of carcinoma, necessitating endoscopic resection. Conventional endoscopic mucosal resection (EMR) often fails to achieve complete resection for intermediate-sized SSLs. Although underwater EMR (UEMR) is being increasingly used for colon polyps, its efficacy for SSLs remains unclear. This study evaluated the complete resection rate of UEMR for intermediate-sized SSLs.

Methods: This prospective, single-arm, observational study was conducted at two institutions. Patients with endoscopically diagnosed intermediate-sized SSLs (10-20 mm) were enrolled. UEMR was performed, and specimens were histologically assessed. Post-UEMR lesions were closely examined, and biopsies were taken to check for residuals. Follow-up colonoscopy was performed 1 year later to evaluate recurrence. The primary end-point was the complete resection rate, defined as no residual in biopsy specimens. The secondary end-points were the rates of R0 resection, en bloc resection, recurrence, adverse events, and factors regarding procedural difficulty.

Results: In total, 103 patients with 133 lesions were consecutively identified. Twenty-seven cases with 30 lesions were excluded by criteria; 103 endoscopically diagnosed SSLs were enrolled. The median postresection lesion size was 12 mm (range 8-23). The R0 and en bloc resection rates were 61% and 91%, respectively. The overall complete resection rate was 97% (95% confidence interval 91.8-99.0%). Follow-up colonoscopy in 87 lesions showed no recurrence. Only one patient (1%) experienced delayed bleeding. Snaring difficulty was significantly associated with piecemeal resection.

Conclusions: The complete resection rate of UEMR for intermediate-sized SSLs was acceptable. UEMR may become a standard treatment for intermediate-sized SSLs.