Usually, liver, gallbladder and spleen ultrasound examinations are recommended to be performed after 8 hours of fasting to avoid affecting its results. Ultrasound of liver, gallbladder and spleen mainly uses ultrasound to examine the liver, gallbladder and spleen, and ultrasound has poor penetration ability to gas. If the food is not completely emptied before the examination, it will easily lead to gas production in the gastrointestinal tract, which will affect the examination of the liver, gallbladder and spleen, and even prevent the corresponding organs or tissues from being seen clearly. Therefore, it is important to ensure the fasting state during the examination to reduce the interference of the contents and gas in the gastrointestinal tract, and to enable the gallbladder to be filled with bile and have better tension of the gallbladder wall for easy observation. Gastric emptying time is about 2-3 hours, protein and fat food emptying in about 4-5 hours. So fasting for 8 hours basically ensures gastrointestinal emptying. Some diseases such as intestinal obstruction or gastrointestinal paralysis may be relatively delayed. Sometimes to observe the contractile function of the gallbladder, a postprandial examination (done after eating an omelette) is also done. If the examination is obstructed by gas-containing organs, further CT or MRI may be performed. In addition, you should avoid drinking alcohol and eating greasy gas-producing foods such as soy products and sweet drinks for 3 days before the liver, gallbladder and spleen ultrasound.