LAUSR

This 44-year–old male sustained injury in a motor vehicle accident. Due to suspicion of intra-abdominal trauma, ultrasonography was performed. Figure 1 shows peritoneal stripe enhancement with reverberation artifact deep to the peritoneal line. This is consistent with free air within the abdomen. Adjacent to the air collection is a fluid-filled intestinal structure with a thin peritoneal stripe. As there is no interposed air between the peritoneum and the intestinal structure, there is no free air at this site. Video 1 shows another finding of abdominal free air. At the interface of the air collection and fluid-filled intestine, there is a mobile interface. This results from movement of the fluid-filled gut structure into the adjacent abdominal free air collection due to transmission of diaphragm excursion and/or aortic pulsations. This may also occur at the interface of free air and intrabdominal fluid. The finding is akin to a lung point seen with thoracic ultrasonography that results from the intermittent respirophasic movement of the partially deflated lung into the pneumothorax space. The same dynamic occurs with abdominal free air, where the intestinal structure is seen to move in and out the free air collection. Given the similarity of mechanism, this could be termed an “abdominal point”, the finding of which is consistent with abdominal free air. Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s0013 4-019-05576 -3) contains supplementary material, which is available to authorized users.