Focused assessment with sonography for trauma

Focused abdominal ultrasound for trauma, commonly abbreviated as FAST and also known as focused assessment with sonography for trauma, is a rapid, bedside, ultrasound examination performed by surgeons and emergency physicians to screen for significant hemoperitoneum or pericardial tamponade after trauma.

The four areas that are examined for free fluid are the perihepatic (hepato-renal space), perisplenic space, pericardium, and the pelvis. With this technique it is possible to identify the presence of free intraperitoneal or pericardial fluid, which in the context of traumatic injury, is usually due to bleeding.

Advantages
FAST is less invasive than diagnostic peritoneal lavage and less costly than computed tomography, but achieves a similar accuracy.

Interpretation
In hemodynamically unstable patients, a positive FAST result suggests hemoperitoneum and laparotomy should be performed in most cases. In hemodynamically unstable patients with a negative FAST result, a search for extra-abdominal sources of bleeding should be performed. In hemodynamically stable patients, a positive FAST result should be followed by a CT scan to better define the nature of the injuries.