Eight preoperative examinations are a series of routine examinations to evaluate patients' physical condition and surgical risk before operation. These tests include blood routine, urine routine, stool routine, liver and kidney function, blood sugar, coagulation function, infectious disease examination and chest X-ray examination. According to medical practice and experience, the results of these examination items are usually valid within three months. In this time range, the examination results can reflect the patient's physical condition and provide important reference for surgery. However, after more than three months, the examination results may no longer be accurate due to possible changes in physical condition. Therefore, if the results of eight preoperative examinations exceed three months, it is usually necessary to re-examine them to ensure the safety and effectiveness of the operation.