Mobile turbid percussion, which is an indirect percussion method, is a method to determine the amount of fluid in the abdominal cavity. When the amount of peritoneal fluid in the abdominal cavity is greater than 1000 ml, mobile turbid sound is usually positive. When the percussion sound changes from a drum sound to a turbid sound, the patient is asked to turn to his side and percuss the same position, and the percussion sound changes from a turbid sound to a drum sound again, indicating that the mobile turbid sound is positive. The same method is used to verify the other side, and the percussion is performed from the center to both sides along the umbilical level. When the percussion changes from a drum sound to a turbid sound, the patient is asked to turn over and the trigger finger is not moved, and the percussion sound changes from a turbid sound to a drum sound again, indicating that the mobile turbid sound is positive and vice versa.