The comet tail sign belongs to the common terminology of ultrasound description and is an artifact in ultrasound imaging, usually encountered during gallbladder, bile duct and gynecological examinations, and is a special image formed by the ultrasound after multiple reverberations. Since this echo resembles the tail of a comet, it is called the comet tail sign. This condition is often seen in ultrasound diagnosis of strong echoes formed by intrauterine devices, intermural stones of the gallbladder, and strong echoes produced by intrahepatic bile duct pneumatization, and can be used as a diagnostic aid for this feature.