CT examination of chest for rectal cancer can determine whether there are contraindications to surgery and whether there is lung metastasis of rectal cancer. 1. Contraindications to surgery: CT examination of chest can be performed before surgery to determine whether there are a series of lesions such as lung lesions, pneumonia, pulmonary atelectasis and so on, which may affect the surgery. 2. Lung metastasis: lung is one of the most common metastatic sites of rectal cancer, and the metastatic foci often involve bronchial tubes and may be accompanied by mediastinal metastasis, patients may have symptoms such as chest pain, coughing up sputum, hemoptysis, shortness of breath, superior vena cava syndrome and so on, which can be examined by CT of chest to assist in judging whether there are metastases in the lung or not. If suffering from rectal cancer, one should seek for medical treatment in time, and the relevant examination should be performed under the doctor’s advice.