Focused assessment with sonography for trauma

Focused Assessment with Sonography for Trauma (commonly abbreviated as FAST) is a rapid bedside ultrasound examination performed by surgeons and emergency physicians as a screening test for blood around the heart (pericardial tamponade) or abdominal organs (hemoperitoneum) after trauma.

The four areas that are examined for free fluid are the perihepatic space (also called Morrison's pouch or the hepatorenal recess), perisplenic space, pericardium, and the pelvis. With this technique it is possible to identify the presence of intraperitoneal or pericardial free fluid. In the context of traumatic injury, this fluid will usually be due to bleeding.

Advantages
FAST is less invasive than diagnostic peritoneal lavage, involves no exposure to radiation and is cheaper compared to computed tomography, but achieves a similar accuracy.

Numerous studies have shown FAST is useful in evaluating trauma patients. It also appears to make emergency department care faster and better. However, some authorities still have not accepted its use.

Interpretation
FAST is most useful in trauma patients who are hemodynamically unstable. A positive FAST result is defined as the appearance of a dark ("anechoic") strip in the dependent areas of the peritoneum. In the right upper quadrant this typically appears in Morison's Pouch (between the liver and kidney). In the left upper quadrant, blood may collect anywhere around the spleen (perisplenic space). In the pelvis, blood generally pools behind the bladder (in the rectovesicular space or Pouch of Douglas). A positive results suggests hemoperitoneum; often CT scan will be performed if the patient is stable or a laparotomy if unstable. In those with a negative FAST result, a search for extra-abdominal sources of bleeding may still need to be performed.