Focused Abdominal Sonography for Trauma
(FAST)

Abdominal ultrasound has been used to evaluate trauma patients in Europe since the 1970's. The German surgery board has required certification in US skills since 1988. Over the last 10 years in the United States, the use of US in trauma has gone from non-existent in most centers to now essentially replacing diagnostic peritoneal lavage (DPL) in many centers. Most recently the FAST exam has been included as part of the Advanced Trauma Life Support (ATLS) course. In addition, The American College of Surgeons has included ultrasound as one of several "new technologies" that surgical residents must be exposed to in their curriculum. It is evident that to more rapidly evaluate blunt abdominal trauma, emergency physicians must become proficient in the use trauma ultrasound.

The FAST exam's only objective is the detection of free intraperitoneal fluid in blunt abdominal trauma. A CT scan provides excellent solid organ detail, but it is expensive and often requires transport of the patient outside the department. DPL is more sensitive for detecting intraperitoneal blood than US. It is usually considered positive with 100,000 RBCs/mm3 which is 20 ml of blood per liter of lavage fluid US is reliably sensitive to usually greater than 250ml in Morrison's Pouch.

DPL, however, is invasive and often complicated by pregnancy or previous surgery. US is inexpensive, rapid, and easily repeated. There is an overwhelming amount of current data supporting the use of the FAST exam as the initial screening tool for evaluation of the abdomen in blunt trauma. Since all hemoperitoneum does not need surgical intervention, further more specific studies such as CT scan may be warranted in stable patients. If positive, the unstable patient goes to the operating room, a stable patient is evaluated by CT scan. If the US is negative in the stable patient, no further exams are indicated unless the patient has severe abdominal pain or there is a change in the clinical condition. In these patients, further evaluation is indicated with repeat US, CT scan or laparotomy.

The FAST exam is performed by utilizing 4 views:

  1. Morrison's Pouch -- This image visualizes the right upper quadrant at the interface between the liver and Gerota's fascia of the kidney known as Morrison's Pouch
  2. Perisplenic View -- This view of the left upper quadrant visualizes the kidney and spleen interface
  3. Pelvic View -- The third image identifies the rectovesicular pouch in males and the cul-de-sac in females utilizing both transverse and longitudinal views of the pelvis This is the most sensitive of the abdominal views with less than 200 cc of fluid sometimes seen.
  4. The Pericardium -- The last view takes us outside the peritoneum to evaluate for pericardial effusion by placing the probe just to the right of the patient's xiphoid. The ultrasound beam is then focused through the liver thus visualizing the interface of the right ventricle and the pericardium


Emergency physicians provide the primary stabilization of trauma victims in the vast majority of institutions without the benefit of a radiologist at bedside. This fact coupled with the reality that the morbidity and mortality associated with trauma increases the longer life-threatening injuries are left undiagnosed makes ultrasound a priceless tool for the ED physician treating the traumatized patient. Upon discovery of intraperitoneal fluid, the emergency physician can then mobilize the onsite surgery team or rapidly transfer the patient depending on the hospital's resources. Multiple studies have supported the use of trauma US by both ED physicians and surgeons. Training in the FAST exam ranges from only 2 hours to greater than 8 and 10 hours with sensitivities/specificities of 75% / 96%, 81% / 99%, and 90% / 99% respectively.

One can not forget the limitations of this study and significant injuries can be missed even in the hands of the most experienced ultrasonographer. However, when used appropriately diagnostic US in trauma allows the emergency physician to rapidly assess, reassess and correctly disposition trauma patients.