Gastric conduit ischemia or anastomotic breakdown after esophagectomy with cervical esophagogastrostomy often cause severe complications, such as leakage, necrotic organs, and strictures. However the evaluation and prevention before developing gastric conduit ischemia have been established. The investigators have built a hypothesis that the evaluation for gastric mucosal ischemia in early phase after esophagectomy predict the complication of gastric conduit. Thus, the purpose of this study is the safety and efficacy of endoscopic evaluation about reconstructive organs after esophagectomy. The investigators evaluate endoscopic predictions using classifications in acute phase after esophagogastrostomy.