Shifting Gas Artefact Sign: Early sonographic detection of pneumoperitoneum.

This case report describes the use of ultrasound to diagnose pneumoperitoneum in an unstable patient with abdominal pain. Gas in peritoneum produces a specific sonographic appearance. The use of dynamic manoeuvres improves confidence in the ultrasound diagnosis of free gas. The Shifting Gas Artefact Sign is explained. The literature on sonographic detection of pneumoperitoneum is reviewed. The detection of pneumoperitoneum is a significant finding in non-traumatic abdominal pain and also in blunt abdominal trauma. In both settings more research is required to validate the utility of the test in the acute setting.