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Ultrasound - FAST

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Trauma with risk of thoracic or abdominal injury

Suspected free abdominal fluid (ascites or ruptured ectopic pregnancy)

Contraindications (absolute in bold)

Airway management or resuscitation required

Indication for emergent laparotomy (e.g. shock with stab wound to abdomen)


CT scanning

Operative intervention (laparotomy or thoracotomy)

Informed consent

Medical emergency

Consent is not required if the patient lacks capacity or is unable to consent

Brief verbal discussion is recommended if the situation allows


Verbal consent

Less complex non-emergency procedure with low risk of complications

Potential complications

Failure to visualise structures (bowel gas, excess tissue, pain)

Failure of image interpretation (false negative or positive)

Procedural hygiene

Standard precautions

PPE: non-sterile gloves


Any bed


Procedural clinician



Ultrasound machine and gel

Linear ultrasound probe (lung)

Curvilinear ultrasound probe (abdomen)



Ultrasound depth 5cm for anterior lung, 20cm for pericardium and abdomen

Lung: probe longitudinally at the midclavicular line, and using RUQ and LUQ views slid 1-2 rib spaces towards the head

RUQ: Probe vertical between ribs 8-11 at mid-axillary line (marker to patient’s head) with anticlockwise rotation

LUQ: Probe vertical between ribs 6-9 at left posterior axillary line (marker to patient’s head) with clockwise rotation

Suprapubic: probe 2cm superior to symphysis pubis in two planes (marker to patient’s right and head)

Subxiphoid: probe inferior to xiphoid directed towards patient’s left shoulder (marker to patient’s right)


Lung view: identify lung slide in more than three sites and look for haemothorax in axilla

RUQ view: identify anechoic fluid in Morrison’s pouch and around tip of liver

LUQ view: identify anechoic fluid in splenorenal recess and around tip of spleen

Suprapubic view (two planes): identify anechoic fluid in recto-vesicular space (males) or pouch of Douglas (females)

Subxiphoid view: identify anechoic strip of fluid in pericardial space

Post-procedure care

Clean ultrasound gel from patient

Initiate further management if required

Document results


Start scanning in the area most likely to yield results (RUQ in blunt trauma, lung and heart in chest trauma)

The liver is a useful acoustic window for both the subxiphoid and RUQ views

A 1cm stripe of anechoic stripe in Morrison’s pouch correlates to approximately 1 litre of fluid


FAST can be performed in less than three minutes and can reliably detect 200ml in the peritoneum. The utility of a FAST depends on the patient population. It almost 100% sensitive in hypotensive blunt trauma patients, meaning that a well-performed scan demonstrating no free fluid rules out the need for immediate emergency laparotomy.

Sensitivity falls in normotensive patients as some clinically significant injuries are not demonstrated by ultrasound (e.g. diaphragm tears, pancreatic lesions, bowel perforations), and other injuries may not have bled enough to be detectable (e.g. early mesenteric injury) on an initial scan. Serial ultrasound improves sensitivity and can detect haemorrhage accumulating over time.

If significant injury is suspected and the FAST examination is negative, the haemodynamically stable patient requires further imaging (usually CT).

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

Please direct feedback for this procedure to


Roberts JR, Custalow CB, Thomsen TW. Roberts and Hedges’ clinical procedures in emergency medicine and acute care. 7th ed. Philadelphia, PA: Elsevier; 2019.

Dunn RJ, Borland M, O’Brien D (eds.). The emergency medicine manual. Online ed. Tennyson, SA: Venom Publishing; 2019.

Manoj P, et al (2019): In: UpToDate. Waltham (MA): UpToDate.: Emergency ultrasound in adults with abdominal and thoracic trauma

Emergency ultrasound imaging criteria compendium. Ann Emerg Med. 2016;68(1):e11-e48. doi:10.1016/j.annemergmed.2016.04.028

Dawson M, Mallin M. Introduction to bedside ultrasound: volume 1. New York NY: Apple Books; 2013.

Dawson M, Mallin M. Introduction to bedside ultrasound: volume 2. New York NY: Apple Books; 2013.

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