Gel Immersion vs. Water Immersion Endoscopic Ultrasound for Visualization of the Duodenal Papilla and Periampullary Lesions: A Dual-Center Retrospective Study With Blinded Evaluation of Archived Videos.

BACKGROUND AND STUDY AIMS: Accurate visualization of the duodenal papilla is essential during endoscopic ultrasound (EUS). Water immersion (WI)-EUS improves papillary visibility by expanding the duodenal lumen, but maintaining sufficient water can be difficult. Gel immersion (GI)-EUS offers more stable visualization, though comparative data remain limited.

PATIENTS AND

METHODS

This dual-center retrospective study included 200 patients who underwent GI-EUS (n = 101) or WI-EUS (n = 99) for ampullary evaluation. Archived videos were randomized and independently assessed by two blinded pancreatobiliary EUS experts. Delineation quality was evaluated using predefined parameters: duodenal distension, liquid retention, and artifact reduction. Optimal delineation success was defined as complete scores for all parameters.

RESULTS

GI-EUS achieved a significantly higher optimal delineation success rate than WI-EUS (60.4% vs. 32.3%, p < 0.001) while requiring less liquid volume (100 mL vs. 150 mL, p < 0.001). Multivariable analysis identified GI as an independent factor associated with delineation success (adjusted OR: 2.83, 95% CI: 1.43-5.57). Inter-observer agreement was substantial, and adverse event rates were similarly low between groups.

CONCLUSIONS

Compared with WI, GI-EUS significantly improves ampullary delineation with enhanced liquid stability and clarity, supporting clinical utility in pancreatobiliary EUS evaluations.