Abstract： Objective To investigate diagnosis and treatment of concealed intrathoracic anastomotic leak of the esophagus. Methods We retrospectively analyzed the clinical data of 32 patients who presented with unexplained sepsis （temperature＞38 ℃ and elevated white blood cell count） after esophagectomy and intrathoracic anastomosis for esophageal carcinoma or gastric cardia carcinoma in Affiliated Hospital, Medical College of Qingdao University from January 2006 to December 2010. All the patients underwent oral water-soluble contrast esophagogram and oral water-soluble contrast computerized tomography of the chest. None of the patients had any sign of contrast leak in these diagnostic examinations, but their chest computerized tomography all showed peri-anastomotic bubble and encapsulated effusion. Fifteen patients were treated as concealed intrathoracic anastomotic leak of the esophagus, including fasting, broad spectrum antibiotic treatment, prolonged gastrointestinal decompression and enteral nutrition via naso-intestinal feeding tube. The other 17 patients were not treated as anastomotic leak of the esophagus and only received broad spectrum antibiotic treatment. Results None of the 15 patients who were treated as concealed intrathoracic anastomotic leak finally developed anastomotic leak proved by oral water-soluble contrast esophagogram and computerized tomography of the chest （0%, 0/15）. Among the 17 patients who were not treated as anastomotic leak, fourteen patients developed anastomotic leak later （82.4%, 14/17）, 2 patients died of aorto-esophageal fistula and 3 patients died of multiple organ dysfunction syndrome. Conclusion Peri-anastomotic bubble and irregular encapsulated effusion in oral water-soluble contrast esophagogram and computerized tomography of the chest should be considered as specific signs of concealed intrathoracic anastomotic leak of esophagus after esophagectomy and intrathoracic anastomosis. Patients with such signs should be treated as anastomotic leak.