In suspected esophageal perforation a water-soluble (Gastrografin) swallow is the preferred contrast study. Barium should not be used because it leaks into the mediastinum and pleura and provokes inflammation and fibrosis. CT chest is an accepted imaging study for perforation. One source also says endoscopy is avoided in perforation, but endoscopy is not an imaging study, so barium swallow is the intended answer.