P525 Utilisation of endoscopic ultrasonography for submucosal cushion measurement to determine eligibility for endoscopic submucosal dissection in ulcerative colitis-associated dysplasia: A case series

Background Endoscopic submucosal dissection (ESD) has gained traction as an effective therapy for ulcerative colitis (UC)-associated dysplasia, yet identifying fitting ESD candidates is challenging by substantial submucosal (SM) fibrosis from chronic inflammation. We report our experience utilising endoscopic ultrasonography (EUS) to assess ESD eligibility by measuring SM cushion thickness. Methods Retrospective case-series includes nine patients who were diagnosed or referred to as UC-associated dysplasia in surveillance colonoscopies between August 2017 and October 2023. After scanning dysplastic lesions (Fig A-B), hyaluronic acid solution was injected into the SM layer (Fig C). EUS with a mini-probe quantified SM cushion beneath the dysplastic lesion (Fig D), and ESD was performed in cases with at least 2.0 mm of SM cushion thickness (Fig E-F). Results Among ten cases from nine patients, eight cases met the criteria and underwent ESD, while two cases (Patient 3, Patient 7) were regarded as unsuitable for ESD with SM cushion thickness less than 2.0 mm. Median disease duration was 19 years, and median age at diagnosis of UC-associated dysplasia was 50 years. Median SM cushion thickness ranged from 4.2 to 6.9 mm. Median procedure time was 50 minutes, and median size of resected specimens and lesions were 31.5 x 24.5 mm and 16.0 x 12.5 mm, respectively. en bloc resection was achieved in all cases, with an 87.5% R0 resection rate. No perforation occurred; only one required post-discharge endoscopic bleeding control after four days post-discharge. Conclusion EUS-measured SM cushion thickness may be a valid approach that provides an objective criterion for determining ESD eligibility in UC-associated dysplasia. This would help guide individualised treatment in UC-associated dysplasia, reducing unnecessary procedures or surgery.