Ultrasound for gallbladder stones can be done with water. Except in emergency cases, gallbladder stones should be performed with fasting to obtain the best images of the gallbladder. Patients should fast for at least 8 hours to allow optimal filling of the gallbladder and minimal gas in the intestines, but drinking water has no effect on the gallbladder. Gallbladder examination is best performed in the morning, when there is less gas in the gastrointestinal tract, because some patients still have a large amount of intestinal gas in the intestine even after fasting, such patients can take some oral anti-flatulence tablets 1-2 days before the examination again to eliminate the gas in the gastrointestinal tract. Barium may interfere with ultrasound examination, so barium imaging of the gastrointestinal tract and biliary system should generally be avoided within 2 days before ultrasound examination.