Ultrasound examination of the abdomen usually requires an empty stomach. Usually, ultrasound of the liver, gallbladder, pancreas, spleen and other organs is done at the same time, collectively called abdominal ultrasound, which is also the main parenchymal organ of the digestive system. The gallbladder is an important organ for storing bile. After eating, bile is discharged from the gallbladder, which affects the observation of the gallbladder, and if there is a lesion, it cannot be seen clearly. After fasting, the normal gallbladder will store more and more bile, and the cavity can be clearly shown under ultrasound to be filled with echoless bile, and if there is a lesion in it, it will be clearly visible. Therefore, it is usually necessary for the patient being examined to fast for more than 6 hours before performing an abdominal ultrasound, including of course an ultrasound of the liver.