Focused Assessment with Sonography in Trauma (FAST)

Last Updated on August 19, 2026

Introduction

Indication: To detect free fluid (e.g. haemoperitoneum, free pericardial fluid, free pleural fluid)

Preparation

Position of patient: supine
Preset: Abdominal
Probe: Curvilinear, B mode

4 quadrants

(i) Subxiphoid / Subcostal – Pericardium

• Over epigastrium, almost in coronal plane
• Find the ‘heart shape’ during scan, look for pericardial collection
• Use liver as acoustic window

(ii) Right upper quadrant – Morrison’s pouch

• Look for hypoechoeic collection at hepato-renal space

(iii) Left upper quadrant – Spleno-renal space

• Look for hypoechoeic collection at spleno-renal space
• Good view includes tip of spleen + inferior pole of kidney

(iv) Pelvis / Suprapubic

• Transverse view: look for fluid in both sides of bladder
• Longitudinal view: look for fluid at rectovesical pouch / rectouterine pouch (i.e. Pouch of Douglas)

Pleural Effusion

• Noted during scan at RUQ / LUQ, esp R4 / L4 area
Features:
• Spine sign during inspiration is suggestive of pleural effusion
• Hypoechoeic collection above diaphragm

Extended FAST (EFAST)

• Involves lung USG to look for pneumothorax

Advantages VS Disadvantages

Advantages

• Can be done in <5 mins
• Can be done bedside & no issue with regards to radiation hazard

Disadvantages

• Unable to visualise parenchymal damage, bowel injury, retroperitoneum, diaphragmatic defect
• Unable to differentiate blood and ascites
• Clotted blood has similar echogenicity as parenchymal tissue, thus could be easily missed

Reference / Further Reading

1. Guide to the Essentials in Emergency Medicine (2nd ed, by Shirley Ooi et al.)
2. FB Amalina Nudin
3. Lung quadrants in lung ultrasound (R1 – R6; L1 – L6)
4. Videos
   (i) https://www.youtube.com/watch?v=l3Xmp4Xq4SQ
   (ii) https://www.youtube.com/watch?v=LrCt0o30ygY
   (iii) https://www.youtube.com/watch?v=JcCZBKSdIRk

Related topics

1. Lung ultrasound