Fasting is required for abdominal CT scan, and patients are generally advised to fast for 4 hours, which can be started after dinner the night before to facilitate the accuracy of the test results the next day. If you eat before the examination, it will promote the emptying of the gallbladder, making it relatively more difficult to observe the gallbladder tissue. In addition, the stomach and intestine are tolerant tissues and organs, and the expansion of the stomach and intestine after eating will also affect the observation to a certain extent. CT scan of abdomen can be divided into upper abdomen, middle abdomen and lower abdomen. Upper abdomen examination mainly includes liver, spleen, pancreas, gallbladder and stomach, middle abdomen mainly includes small intestine, both kidneys and adrenal glands, and lower abdomen mainly includes large intestine and other pelvic organs. It is recommended to fast for 8 hours for the middle abdominal examination, and to take 200-300mL of contrast medium at 8pm and 10pm the night before, and at 6pm and 8pm on the day of the examination, and wait for the bladder to fill up before performing the examination. When performing abdominal CT scan examination, it is necessary to remove clothing from the examination area, including underwear and various items with metallic substances; follow the instructions of the technician during the examination, keep the body position still, and cooperate with the examination by breathing calmly, holding the breath, not swallowing saliva and not blinking, etc.