Evaluation of the Efficacy and Safety of Magnetically-controlled Capsule Gastroscopy for Postoperative Assessment in Elderly Patients and Patients With Underlying Diseases

Inclusion Criteria: * Planned to undergo magnetic-controlled capsule gastroscopy or conventional endoscopy, and have undergone surgery for gastric malignant tumors (including surgical resection and ESD), elderly patients (older than 65 years) or patients with underlying diseases (cardiovascular, respiratory, hemorrhagic diseases, etc.); * Agree to participate in this clinical trial and sign the informed consent form. Exclusion Criteria: * No surgical conditions or refuses abdominal surgery (Once the capsule is stuck it cannot be removed surgically); * Cardiac pacemakers (except MRI-compatible ones); * Electronic implants or metal foreign bodies; * Pregnant women; * Known or suspected GI obstruction, stenosis, fistula; * Dysphagia.