BACKGROUND Our goal was to verify surgical factors that affect duodenogastric reflux (DGR) after esophagectomy through the use of a flow visualization model that would mimic an intrathoracic gastric tube. METHODS Transparent gastric tube models for different routes (retrosternal space [RS] and posterior mediastinum [PM]) were fabricated. Various distal pressures were applied to the experimental model filled with water, and the flow was recorded with a high-speed camera. The volume and maximum height of the refluxate through the pylori of two different sizes (7.5 mm, 15 mm) in two different postures (upright, semi-Fowler) was measured by analyzing the video clips. RESULTS For the large pylorus setting, when the pressures of 20, 30, and 40 mmHg were applied in the upright position, the volumes of the refluxate in the RS/PM tubes were 87.7 ± 1.1/96.4 ± 1.7 mL, 150.8 ± 1.1/158.0 ± 3.2 mL, and 156.8 ± 3.3/198.0 ± 4.7 mL (p < 0.05), and the maximum heights were 101.6 ± 4.8/113.4 ± 2.9 mm, 151.4 ± 2.2/165.4 ± 1.5 mm, and 166.1 ± 1.7/193.7 ± 6.6 mm (p < 0.05). The data for the small pylorus setting or in the semi-Fowler position showed similar tendencies. For any given route, posture or pressure setting, DGR in the large pylorus model was definitively higher than that for small one. CONCLUSIONS This fluid mechanics study demonstrates posterior mediastinal gastric interposition or pyloric drainage procedure, or both, is associated with high reflux of duodenal contents.