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Point-of-care ultrasound in the emergency department and eFAST
Bedside ultrasound answers yes-or-no questions in real time — is there blood in the abdomen, fluid around the heart, a pneumothorax, poor cardiac function or an abdominal aneurysm — and supports a rapid decision in an unstable patient; a negative scan does not exclude injury in a stable patient.
Why it matters in the exam
FAST questions test the four windows — the right upper quadrant (Morison's pouch, the most sensitive window), the left upper quadrant, the pelvis and the subxiphoid window for the pericardium — and the eFAST addition: two anterior chest windows for pneumothorax. The decision is asked: an unstable patient with a positive abdominal FAST — theatre; an unstable patient with a negative FAST — look for another bleeding source (chest, pelvis, long bones, retroperitoneum).
Limitations are also tested: FAST detects free fluid only from a volume of about 200 mL, is insensitive to retroperitoneal and bowel injuries, and a negative scan in a stable patient does not replace CT. In the lung, absent pleural "sliding" suggests pneumothorax, and the "lung point" is a highly specific sign; diffuse B-lines indicate pulmonary oedema.
Beyond trauma, POCUS is used in unexplained shock (the RUSH protocol: heart, inferior vena cava, abdomen, aorta and lungs), in cardiac arrest to detect cardiac activity, tamponade or a dilated right ventricle — without extending compression pauses beyond 10 seconds — and in suspected abdominal aortic aneurysm, where a diameter of 3 cm or more is diagnostic. Two-point compression diagnoses deep vein thrombosis, and ultrasound guidance improves success in venous cannulation.
Key points
- FAST: right upper quadrant, left upper quadrant, pelvis and heart; eFAST adds the chest.
- Unstable with a positive FAST — theatre.
- FAST detects fluid from about 200 mL; insensitive to the retroperitoneum and bowel.
- Absent sliding — pneumothorax; lung point — highly specific.
- RUSH in shock; in cardiac arrest — pauses of up to 10 seconds only.
Summary table
| Question | Window | Positive finding | Decision |
|---|---|---|---|
| Blood in the abdomen | Right upper quadrant, left upper quadrant, pelvis | Black (anechoic) fluid between organs | Unstable — theatre |
| Tamponade | Subxiphoid | Pericardial fluid and diastolic right ventricular collapse | Pericardiocentesis or surgery |
| Pneumothorax | Anterior chest windows | Absent sliding, lung point | Needle decompression or a drain |
| Abdominal aortic aneurysm | Abdomen, midline | Diameter 3 cm or more | Unstable — urgent vascular surgery |
| Unexplained shock | RUSH | Small hyperdynamic heart, dilated right ventricle, B-lines | Points to the type of shock |
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Sources
- ACEP Ultrasound Guidelines: Emergency, Point-of-Care and Clinical Ultrasound Guidelines in Medicine, 2023 — Core applications
- ATLS Advanced Trauma Life Support, Student Course Manual (American College of Surgeons), 10th edition (2018) — FAST as an adjunct to the primary survey
- International evidence-based recommendations for point-of-care lung ultrasound (Intensive Care Medicine), 2012 — Pneumothorax and interstitial syndrome
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.