Enhanced CT is one of the CT examination methods, which requires the injection of contrast agents, commonly used are iodophoresol, iopromide or iodixanol. The radiation dose of enhanced CT is higher than that of plain CT, but it is within the normal range and does not cause any harm to the human body. The contrast agent injected in enhanced CT is metabolized by the kidney function. If the patient’s kidney function is not adequate, the contrast agent injection may aggravate the damage to the kidney function, so it should be done with caution if the patient has kidney insufficiency. Injection of contrast agent may cause allergic reactions in patients. If patients are allergic to iodine contrast agent or have allergies, the chance of allergic reactions is relatively high, and severe allergic reactions may even result in severe laryngeal edema, bronchospasm, coma and shock. After the enhancement CT, doctors usually advise patients to drink as much water as possible to help the discharge of the contrast agent.