Focused Assessment with Sonography in Trauma (FAST)
1. Purpose & Scope
The FAST exam is a rapid, bedside ultrasound protocol used in the initial evaluation of blunt or penetrating trauma patients to identify free intraperitoneal fluid (primarily blood).
2. The Four Standard Views
- RUQ (Perihepatic/Morison’s Pouch): The most sensitive view for detecting free fluid. Look between the liver and the right kidney.
- LUQ (Perisplenic): Look between the spleen and the left kidney/diaphragm.
- Suprapubic (Pelvic): Look in the rectovesical or rectouterine (Pouch of Douglas) space.
- Subxiphoid (Pericardial): Look for pericardial effusion (specifically for cardiac tamponade).
3. eFAST (Extended FAST)
The eFAST adds bilateral lung views to screen for pneumothorax. The absence of “lung sliding” and “comet-tail” artifacts suggests a pneumothorax.
4. High-Yield Clinical Pearls
| Scenario | Action |
|---|---|
| Positive FAST + Unstable | Proceed directly to laparotomy. |
| Positive FAST + Stable | Proceed to CT imaging to grade the solid organ injury. |
| Negative FAST | Does not rule out injury (e.g., retroperitoneal or bowel injury). If clinical suspicion remains high, obtain a CT or repeat FAST. |
5. Important Limitations
- FAST is poor at evaluating retroperitoneal injuries (e.g., pancreas, duodenum).
- It cannot reliably distinguish blood from ascites or urine in the acute setting.