Figure 4: (a) A right lateral thoracic radiograph shows a 3-month-old male German Shepherd presenting for regurgitation and retching. There is gas distention of the cranial thoracic esophagus and a large soft tissue dense mass visible in the caudal dorsal thorax. A gas-soft tissue interface is seen at the cranial margin of the mass (black arrows) indicating that the mass resides within the esophagus. The trachea is displaced ventrally (white arrows). The stomach is not visualized in the abdomen. (b) A right lateral thoracic radiograph of the same dog as in (a) following the administration of liquid barium confirms that the mass is in the esophagus. There are rugal folds on the surface of the mass (white arrows) verifying the diagnosis of gastroesophageal intussusception.