Fig. 5

Proposed approach using bedside ultrasound for patients with abdominal pain and hemodynamic instability. If air is present anterior to the liver or spleen (in the absence of a recent abdominal surgery) during both inspiration and expiration, a pneumoperitoneum should be suspected. A pneumoretroperitoneum will be associated with air behind the liver hiding the inferior vena cava (IVC). Venous gas embolism will be associated with air in the liver typically in the portal vein mostly in the peripheral regions of the liver. Air embolism can also be seen in the hepatic vein and the IVC. Finally pneumatosis intestinalis is characterized by air in the bowel lumen