The size of the gallbladder usually shrinks to 1/2 or less of its original size after a meal in normal people. The volume of the gallbladder in normal people changes with eating. When eating, the gallbladder contracts to expel bile and the volume shrinks. During fasting, the gallbladder volume increases, which is mainly the result of the coordination between bile discharge, storage and eating. Clinical ultrasound of the gallbladder is generally used to observe the changes in gallbladder size during fasting and after a fatty meal, and is used to determine whether the gallbladder contraction function is normal. Compare the results measured before and after the fat meal, if the gallbladder function is normal, half an hour after the fat meal, the gallbladder volume should be reduced to 1/2 or smaller, in order to check whether the gallbladder contraction and emptying function is normal or not. In patients with cholecystitis and gallbladder stones, especially those with frequent attacks, the gallbladder shrinks due to repeated inflammation, becomes smaller and smaller in volume, and loses its ability to contract, and may eventually lose its function completely.