Utility of Underwater Peroral Endoscopic Myotomy with Near Focus Magnification for Severe Submucosal Fibrosis

Background Severe submucosal fibrosis (SMF) is the strongest predictor of technical failure and prolonged procedure time in conventional peroral endoscopic myotomy (POEM). Underwater POEM (uPOEM) may offer advantages in fibrotic cases, but its effectiveness remains unexplored. Methods This single-centre, retrospective case series of consecutive patients who underwent uPOEM using near focus magnification for achalasia with SMF between July 2024 and December 2025. Results Of 153 POEM procedures, 12 patients had SMF (median age 56 [52–63] years, symptom duration 9 [7.2–10] years). Four were treatment-naive. Eight had type I (66.7%) and four (33.3%) type II achalasia. Sigmoid esophagus (S1) was present in 3 (25%), S2 in 2 (16.7%), and straight type in 7 (58.3%). The median IRP was 30 (27–33) mmHg. uPOEM was successfully completed in all 12 patients (100%) with near focus magnification in whom uPOEM-assisted tunneling was initiated, after exclusion of one aborted pre-tunneling case. The median procedure time was 54 (52–58) minutes. One patient had a mucosal breach (Type I), managed with hemoclips. The median Eckardt score decreased significantly from 7 to 0 at 3 months (p<0.001). Conclusions uPOEM is safe and appeared feasible in severe SMF, yielding favorable short-term outcomes. Near focus magnification allows better identification of the submucosal layer allowing for more precise dissection.