Elevated CEA in clinical examination is most commonly seen in diseases such as rectal cancer, pancreatic cancer and breast cancer. Therefore, for patients with high CEA, the following examination protocols are mainly recommended: 1. Improve blood routine, liver and kidney function examination to clarify whether there are any causes of tumor that cause anemia and liver and kidney insufficiency. 2. Improve colonoscopy to exclude malignant tumor of colon and rectum. If intestinal occupying lesions are found under colonoscopy, biopsy should be performed to further clarify the nature of the lesion, and once the lesion is clearly malignant, surgery should be performed as soon as possible. 3. If no abnormality is found in the relevant examination, it is recommended to recheck CEA in 2-3 months, because enteritis and gastritis may also cause mildly high index.