We represent the US findings of isolated gallbladder rupture caused by blunt abdominal trauma in a 13-year-old boy. At the initial US examination, although a pericholecystic fluid collection was observed, the mildly collapsed gallbladder was regarded as a contracted gallbladder. Even though the patient was haemodynamically stable, repeat US examination after 24 h revealed gallbladder perforation. In haemodynamically stable trauma patients repeated US examinations can be useful and are strongly recommended.