Focussed Assessment with Sonography for Trauma (FAST) scan is a point-of-care ultrasound examination performed at the time of presentation of a trauma patient.
It is invariably performed by a clinician, who should be formally trained, and is considered as an 'extension' of the trauma clinical assessment process, to aid rapid decision making. Some studies have shown no significant difference in diagnostic accuracy between radiologists and non-radiologists 6.
The chief aim, and many would say the sole aim, is to identify intra-abdominal free fluid (assumed to be haemoperitoneum in the context of trauma) allowing for an immediate transfer to theatre, CT or other.
Many papers have been published detailing the pros and cons of this investigation 1,2. It has a reported sensitivity of ~90% (range 75-100%) and a specificity of ~95% (range 88-100%) for detecting intraperitoneal fluid 4. Sensitivity for detecting solid organ injuries is much lower.
It has replaced diagnostic peritoneal lavage as the preferred initial method for assessment of haemoperitoneum.
The sensitivity of FAST to assess for pneumothorax is low at ~40% but may still be better than a supine chest x-ray 7.
- patient in supine position
- 3.5-5.0 MHz convex transducer
- five regions may be scanned 3:
- subxiphoid transverse view: assess for pericardial effusion and left lobe liver injuries
- longitudinal view of the right upper quadrant: assess for right liver injuries, right kidney injury, and Morison pouch
- longitudinal view of the left upper quadrant: assess for splenic injury and left kidney injury
- transverse and longitudinal views of the suprapubic region: assess the bladder and pouch of Douglas
An "extended FAST or eFAST" scan may be performed 7:
Causes of false negatives
- obesity: severely limits assessment of the peritoneal cavity
- subcutaneous emphysema
Causes of false positives
- fluid-filled bowel adjacent to the liver, spleen or kidneys
- pre-existing ascites
- epicardial fat pad may mimic haemopericardium
- seminal vesicles mistaking for pevlic free fluid in the young male patient
History and etymology
Ultrasound was first utilised for the examination of trauma patients in the 1970s in Europe 8.
- 1. Dolich MO, McKenney MG, Varela JE et-al. 2,576 ultrasounds for blunt abdominal trauma. J Trauma. 2001;50 (1): 108-12. Pubmed citation
- 2. Natarajan B, Gupta PK, Cemaj S et-al. FAST scan: is it worth doing in hemodynamically stable blunt trauma patients?. Surgery. 2010;148 (4): 695-700. doi:10.1016/j.surg.2010.07.032 - Pubmed citation
- 3. Körner M, Krötz MM, Degenhart C et-al. Current Role of Emergency US in Patients with Major Trauma. Radiographics. 2008;28 (1): 225-42. doi:10.1148/rg.281075047 - Pubmed citation
- 4. Brenchley J, Walker A, Sloan JP et-al. Evaluation of focussed assessment with sonography in trauma (FAST) by UK emergency physicians. Emerg Med J. 2006;23 (6): 446-8. doi:10.1136/emj.2005.026864 - Free text at pubmed - Pubmed citation
- 5. Michalke JA. An overview of emergency ultrasound in the United States. World J Emerg Med. 2014;3 (2): 85-90. Free text at pubmed - Pubmed citation
- 6. Bhoi S, Sinha TP, Ramchandani R et-al. To determine the accuracy of focused assessment with sonography for trauma done by nonradiologists and its comparative analysis with radiologists in emergency department of a level 1 trauma center of India. J Emerg Trauma Shock. 2013;6 (1): 42-6. doi:10.4103/0974-2700.106324 - Free text at pubmed - Pubmed citation
- 7. Abdulrahman Y, Musthafa S, Hakim SY et-al. Utility of extended FAST in blunt chest trauma: is it the time to be used in the ATLS algorithm?. World J Surg. 2015;39 (1): 172-8. doi:10.1007/s00268-014-2781-y - Pubmed citation
- 8. Richards JR, McGahan JP. Focused Assessment with Sonography in Trauma (FAST) in 2017: What Radiologists Can Learn. Radiology. 283 (1): 30-48. doi:10.1148/radiol.2017160107 - Pubmed