CT abdominal examinations require fasting because food and its residues can affect some organs in the abdomen, including the stomach, gallbladder, duodenum, colon and so on. Therefore, you should fast for at least eight hours before having a CT abdominal examination, because if you do not fast, these food residues and feces will appear as artifacts in the images, which will lead to wrong diagnosis and clinical treatment errors, and will bring unnecessary pain and economic loss to the patient, which not only affects clinical treatment, but also may lead to doctor-patient disputes.