FAST and eFAST Scanning
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Direct answer
FAST — focused assessment with sonography in trauma — is a four-window bedside ultrasound that answers one question in minutes: is there free fluid where bleeding would collect? The views are the right upper quadrant (Morison's hepatorenal space and the right pleural space), the left upper quadrant (splenorenal recess), the pelvis (pouch of Douglas or retrovesical space), and the subxiphoid pericardial window; eFAST adds anterior chest views for pneumothorax, where the absence of lung sliding and B-lines is the finding. In the unstable blunt trauma patient, a positive FAST with a compatible mechanism is enough to move to theatre without a CT journey; in the stable patient it is one more data point in a pathway that belongs to CT. FAST sees fluid, not organs — its blind spots define its correct use.
What you must remember
- Four standard windows: right upper quadrant, left upper quadrant, pelvis, pericardial (subxiphoid).
- Free fluid reads black: anechoic stripes in Morison's space, around the spleen, in the pelvis, or a circumferential pericardial stripe.
- The unstable-patient rule: positive FAST plus hypotension equals theatre or a surgical decision, not a CT scanner — the single highest-yield management sentence in trauma ultrasound.
- eFAST chest views: bilateral anterior chest wall scans; absent lung sliding, absent B-lines and (on M-mode) a barcode or stratosphere sign support pneumothorax — more sensitive than a supine chest film for the anterior chest.
- Known blind spots: retroperitoneal haemorrhage, bowel injury, subcapsular haematomas and solid-organ injury without rupture — a negative FAST never excludes intra-abdominal injury.
- Pericardial window wins: tamponade is confirmed in seconds subxiphoidally, and a pericardial stripe in a hypotensive penetrating chest injury is a theatre activation.
- Repeat scanning matters: serial FAST after an interval catches the slow bleeder that the first scan missed — "repeat, not reassure".
- POCUS context: FAST belongs to a family of focused scans (chest, abdominal aorta, cardiac, DVT, pregnancy location) each answering binary questions; none replaces formal imaging or clinical judgement.
Two patients, one probe, two destinations
A 40-year-old falls from a scaffold and arrives hypotensive at 78, abdomen distended. The eFAST runs during resuscitation: Morison's space shows a black stripe between liver and kidney, the pelvis a dependent collection, the pericardial window dry, both chests sliding. Four windows, ninety seconds, one conclusion — free intraperitoneal fluid in an unstable patient — and he goes to theatre with the surgical team, never through a CT gantry where unstable patients die. The second patient is a 25-year-old stabbed in the left chest, pressure 86, neck veins full: the subxiphoid view shows a fluid stripe compressing the right ventricle — tamponade confirmed at the bedside, theatre activated while pericardiocentesis is prepared as a bridge, and the chest views show sliding lung excluding a simultaneous pneumothorax. Same probe, six minutes, two different operations — in both, the scan confirmed what physiology and mechanism had already suggested: focused questions, binary answers, integrated with everything else the hands and the monitor know.
Where students slip
The overreach trap leads: candidates write that FAST excludes intra-abdominal injury — it does not, because retroperitoneal blood, bowel injury and solid-organ lacerations without free fluid all scan "clean", so a negative FAST with ongoing suspicion earns CT or observation, not discharge. The second is indication confusion: FAST shines in the unstable and is subordinate to CT in the stable — the stem sending an unstable patient to "CT abdomen for confirmation" tests exactly this. Third is interpretation detail: clot appears echogenic and may be missed, and a full bladder is needed for the pelvic window — practical points bedside operators learn quickly. Indian viva examiners add the equipment reality — machines are increasingly available even in district hospitals, and the ECCT trainee often owns the probe: questions cover probe handling, gain settings, stored-image documentation, and the honesty of calling formal imaging when the scan is limited by obesity, gas or surgical emphysema.
Frequently asked questions
What are the four windows of the FAST examination?
Right upper quadrant (Morison's space), left upper quadrant (splenorenal recess), pelvis, and the subxiphoid pericardial view — plus anterior chest views in the extended eFAST.
What does a positive FAST with hypotension mandate?
Immediate surgical involvement and theatre-bound management — CT transport is avoided because free fluid with instability means the diagnosis is already made clinically.
Can a negative FAST exclude abdominal injury?
No — retroperitoneal bleeding, bowel injury and solid-organ damage without free fluid can scan normally; persistent suspicion earns CT, serial examination or observation.
How does eFAST detect pneumothorax?
By the absence of lung sliding and B-lines on the anterior chest wall, with a barcode pattern on M-mode — findings more sensitive than a supine radiograph for anterior air.
Roughly how much intraperitoneal fluid is needed before FAST turns positive?
On the order of a few hundred millilitres — commonly quoted near 200 mL or more in the dependent spaces — which is why early or slow bleeds warrant repeat scanning.