Whether or not CT can reveal fluid depends on the location of the fluid and the amount of fluid in the patient. In some patients, the amount of effusion is particularly small, and due to the patient’s body position, CT may not be able to detect it, but for abdominal effusion, pleural effusion, or joint effusion, CT can show it clearly in most cases. Therefore, to see the specific fluid, it is necessary to decide according to the specific location of the patient and the specific situation, and it is possible to choose ultrasound or CT, or to combine the two methods at the same time.