The abdominal ultrasound requires an empty stomach and is best performed after a bowel movement. It is also best to eat less oil and a lighter diet the day before. If variation is needed, then upper abdominal tissues and organs such as liver, gallbladder, pancreas and spleen need to be examined on an empty stomach, while lower abdominal and pelvic tissues and organs such as kidney, ureter, bladder and uterus can be examined without an empty stomach, but some of the examinations need to hold urine. Fasting is a part of the patient’s preparation before the ultrasound examination. If the preparation is not sufficient, it will directly affect the effect of the examination and the accuracy of the diagnosis of the disease. In particular, fasting is required for examinations of the upper abdominal organs such as the biliary system and the liver. Fasting is generally required for at least eight hours, usually after eight o’clock the night before and no food and water after ten o’clock. At the same time, it is best not to consume too greasy food the night before, and try to vegetate and eat as little as possible, so that the gallbladder can be in a state of filling and can fully reveal the lesions in the gallbladder, especially some tiny lesions in the wall and folds of the gallbladder. Otherwise, if there is no fasting, it will be difficult to show clearly the organs such as liver and pancreas located behind the gastrointestinal tract as well as the large blood vessels in the abdomen due to the enlargement of the stomach body and the obscuration of food and air in the gastrointestinal tract. Therefore, the examination of the liver, gallbladder, pancreas and spleen and the examination of the large blood vessels in the abdomen should be performed on an empty stomach. However, emergency patients are not subject to these conditions and can be examined in a timely manner under close observation.