The Truth about the FAST Exam
Nick Tadros, MS4
June 2007
Objectives
• Components of the FAST exam
• Pitfalls of the exam
• History of the exam from a radiology and
EM/Trauma perspective and the Time to
Ultrasound Hypothesis
• Recent research
Focused Assessment by Sonography in Trauma (FAST)
Four Primary Views
• The right upper quadrant
(RUQ)
• The subxiphoid
• The left upper quadrant
(LUQ)
• Suprapubic
• Other views are often
used
• 1/2 of the positive tests
will reveal blood in the
RUQ
Perihepatic
Pelvic
Pericardial
Perisplenic
www.Trauma.org
“Positive” FAST Exam
Normal view of Morrison’s
Pouch
www.medical.philips.com
“Positive” FAST of
Morrison’s Pouch
Pericardial Effusion
Normal subcostal view of pericardium
www.medical.philips.com
“Positive” FAST demonstrating
pericardial effusion
Positive FAST in a Patient with Ascites
Perihepatic fluid collection
Liver parenchyma
www.frca.co.uk/ images/A-031.jpg
The FAST Exam in the Literature
Study
n
sensitivity(%)
specificity(%)
npv(%)
Ballard et al, 1999
102
28
99
85
Boulanger et al, 1996
400
81
97
96
Chiu et al, 1997
772
71
100
98
Coley et al, 2000
107
38
97
78
Hoffmann et al, 1992
291
89
97
93
Ingeman et al, 1996
97
75
96
92
518
73
98
98
Liu et al, 1993
55
92
95
84
McElveen et al, 1997
82
88
98
96
McKenney et al, 1996
996
88
99
98
Rozycki et al, 1993
470
79
96
95
Rozycki et al, 1995
365
90
100
98
Rozycki et al, 1998
1227
78
100
99
Shackford et al, 1999
234
69
98
92
Thomas et al, 1997
300
81
99
98
Tso et al, 1992
163
69
99
96
Wherret et al, 1996
69
85
90
93
Yeo et al, 1999
38
67
97
93
6324
75
98
94
Kern et al, 1997
Total
Courtesy of Mark Brown
Pitfalls in the FAST Exam
•
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•
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Failure to scan Morison's pouch in the vertical plane,
ideally from the midclavicular line. A horizontal
scanning plane in the patient's midaxillary line may
miss free fluid.
Excessive focus on the required views.
Failure to scan systematically and slowly through the
four areas in real time.
Failure to identify clotted blood.
Failure to consider ascites as a cause for free fluid.
The only thing worse than a slow FAST is an
inaccurate FAST.
http://www.cpr.org.tw/ettc/fast_exam.htm
Quantification of Fluid on Screening Ultrasonography
for Blunt Abdominal Trauma
• 2693 patients between April 1994 and Dec 1998
• All examinations were performed in the presence of a staff or
resident radiologist and interpreted prospectively by radiologists.
Patients’ bladders were distended with 200 to 300 mL of sterile
saline via Foley catheter if empty at the start of the examination
• The presence or absence of fluid (free or loculated) in each of the 7
regions examined was recorded. On the basis of a previous study,23
isolated anechoic pockets of fluid in the cul-de-sac in women of
reproductive age were considered physiologic and not included.
• A simple scoring system was developed, which quantified the
amount of fluid attributable to trauma by counting the number of
intraperitoneal and extraperitoneal abdominal recesses in which
nonphysiologic fluid was seen on screening ultrasonography
Sirlin et al. Quantification of fluid on screening ultrasonography for blunt abdominal
trauma: a simple scoring system to predict severity of injury. Journal of Ultrasound in
Medicine. 20(4):359-64, 2001 Apr.
Fluid Score Results
History of the Ultrasound and Trauma
An Emergency Medicine Perspective
• Ultrasound was first described in the detection of free
peritoneal fluid by Goldberg et al in 1970
• Sonography in the evaluation of trauma patients was
developed by European surgeons more than 10 years
later
• Reports of the technique started to appear in the North
American literature in 1989
• First prospective study of ultrasound performed by nonradiologists in this country was published in 1992
• Emergency physician use of this modality was reported
by Jehle et al. in 1993
• Exam became known by the FAST acronym in 1996
Fluid and Ultrasound
Goldberg et al. in 1970 described the
evaluation of ascites by ultrasound, not
blood!
Goldberg BB. Goodman GA. Clearfield HR. Evaluation of ascites by ultrasound. Radiology.
96(1):15-22, 1970 Jul.
The Radiologists Prospective
• Blood is a dynamic substance and is NOT
anechoic initially!
• When a clot begins to retract after a
certain time it leaves behind anechoic
plasma
• Very similar to free fluid
• Hematomas contain a variable amount of
internal echoes during the first month, and
then gradually become anechoic1
1Wicks
JD. Silver TM. Bree RL. Gray scale features of hematomas: an ultrasonic spectrum. American
Journal of Roentgenology. 131(6):977-80, 1978 Dec
1989 Article from Germany
“Sonographically, recent injuries of the
liver show echo-rich, non-homogeneous
lesions which may contain smaller echofree portions. Older lesions become
increasingly devoid of echoes and become
increasingly demarcated from normal liver
parenchyma”
Grabenwoger F. Dock W. Pichler W. Farres MT. Metz V. Diagnosis of liver trauma:
ultrasound versus computed tomography [German] Rofo: Fortschritte auf dem Gebiete
der Rontgenstrahlen und der Nuklearmedizin. 150(2):163-6, 1989 Feb
First American Journal Article
• Sonography versus peritoneal lavage in blunt abdominal
trauma
• Sen 84%
• Accuracy 86%
• Predictive Value 89%
• “The results demonstrate that sonography cannot replace
peritoneal lavage in the diagnosis of blunt abdominal
trauma….sonography and peritoneal lavage are not competing,
but rather, are complementary examinations”
• NO mention of technique or definition of a “positive” ultrasonic
exam
Gruessner R. Mentges B. Duber C. Ruckert K. Rothmund M. Sonography versus peritoneal
lavage in blunt abdominal trauma. Journal of Trauma-Injury Infection & Critical Care. 29(2):242-4,
1989 Feb.
First ER Literature Reference
The presence of an anechoic (black) stripe
between the liver and the right kidney
(Morrison's pouch) was interpreted as a
positive study, and the absence of this
finding was interpreted as a negative
study.
Jehle D. et al. Emergency department ultrasound in the evaluation of blunt abdominal
trauma. American Journal of Emergency Medicine. 11(4):342-6, 1993 Jul.
What did the Radiologists have to say?
B-Mode Sonography of 1980
Phantom Test Box
Think of it like your parent’s 8-track player…
Results of B-Mode Scans
• All fluids imaged sonographically were
clearly detectable as echo-free regions
• The results indicate that internal echoes
within the fluid are not dependent on the
nature or concentration of a solute, nor is
their presence a result of high viscosity
• “Pathologic fluid collections…may
show little acoustic enhancement”
Filly RA. Sommer FG. Minton MJ. Characterization of biological fluids by
ultrasound and computed tomography. Radiology. 134(1):167-71, 1980 Jan.
But…
“Blood clots in water showed a decline in
echogenicity throughout the experiment.
The A-mode imaging was effectively able
to follow blood clot echogenicity changes
under these controlled conditions”
Peter DJ. Flanagan LD. Cranley JJ. Analysis of blood clot echogenicity. Journal of
Clinical Ultrasound. 14(2):111-6, 1986 Feb
Radiology Journals
• Abdomens were scanned for free fluid and for
parenchymal heterogeneity in visceral organs;
scans that depicted these were considered
positive
• In the presence of medical ascites (e.g. cirrhosis
or other cause of nontraumatic intraperitoneal
fluid), free fluid was considered positive because
hemoperitoneum could not be excluded
Farahmand, N, Sirlin, CB, Brown, MA, et al. Hypotensive patients with blunt abdominal
trauma: performance of screening US. Radiology 2005; 235:436
Does Time Matter?
• 72 Patients
• US performed by PGY-2 – PGY-8 (ER Docs?)
• Initial FAST exam 63.5 min after trauma
• 61.2% performed within 60 min
• “If an anechoic or echo-free space was recognized in
Morison’s (hepatorenal) pouch or Douglas’ cul-de-sac,
we took it as hemoperitoneum”
• Sen 86.7%
• Spec 100%
• Accuracy 97.2%
Kimura A, Otsuka T: Emergency center ultrasonography in the evaluation of hemoperitoneum: A
prospective study. J Trauma 31:20, 1991
Kimura A, Otsuka T: Emergency center ultrasonography in the evaluation of hemoperitoneum: A
prospective study. J Trauma 31:20, 1991
Kimura A, Otsuka T: Emergency center ultrasonography in the evaluation of hemoperitoneum: A
prospective study. J Trauma 31:20, 1991
Not so FAST…
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The FAST examination was considered positive if it demonstrated evidence
of free intra-abdominal fluid
FAST examination results were compared with CT scan findings, noting the
discordance
FAST examination had a sensitivity of 42%, a specificity of 98%, a positive
predictive value of 67%, a negative predictive value of 93%, and an
accuracy of 92%
Six patients with false-negative FAST examinations required laparotomy for
intra-abdominal injuries
Of the 313 true-negative FAST examinations, 19 patients were noted to
have intra-abdominal injuries without hemoperitoneum and 11 patients were
noted to have retroperitoneal injuries
Use of FAST examination as a screening tool for blunt abdominal trauma in
the hemodynamically stable trauma patient results in underdiagnosis of
intra-abdominal injury. Hemodynamically stable patients with suspected BAI
should undergo routine CT scanning
Miller, MT, et al. Not so FAST. J Trauma 2003; 54:52
The 2006 SOAP Trial
Sonography Outcomes Assessment Program
PLUS = point-of-care, limited ultrasonography
SOAP Trial Results
• Time to operative care was 64% less for
PLUS compared to control patients.
• PLUS patients
– underwent fewer CTs (odds ratio 0.16)
– spent 27% fewer days in hospital
– had fewer complications (odds ratio 0.16)
– charges were 35% less compared to control
Melniker et al. Randomized controlled clinical trial of point-of-care, limited ultrasonography for trauma in
the emergency department: the first sonography outcomes assessment program trial.. Annals of
Emergency Medicine. 48(3):227-35, 2006 Sep
The Fallacy of the Secondary Examination
• Hypothesis: A repeat abdominal ultrasound may
allow for the duration necessary to accumulate
the prerequisite amount of blood for detection by
the majority of surgical ultrasound operators
• Criteria: Secondary ultrasounds (SUS)
performed between 30 until 24 hours after
admission
• Technique: All US and SUS exams were
considered positive if any intraperitoneal fluid
was identified
Blackbourne et al. Secondary ultrasound examination increases the sensitivity of the FAST exam in
blunt trauma. Journal of Trauma-Injury Infection & Critical Care. 57(5):934-8, 2004 Nov
Blackbourne et al. Secondary ultrasound examination increases the sensitivity of the FAST exam in
blunt trauma. Journal of Trauma-Injury Infection & Critical Care. 57(5):934-8, 2004 Nov
Blackbourne et al. Secondary ultrasound examination increases the sensitivity of the FAST exam in
blunt trauma. Journal of Trauma-Injury Infection & Critical Care. 57(5):934-8, 2004 Nov
Common Myth
Chief of Surgery at Vermont (where Dr. Gosslin trained!)
Rozycki GS, Ochsner MG, Jaffin JH, Champion HR. Prospective evaluation of surgeons’ use
of ultrasound in the evaluation of trauma patients. J Trauma. 1993; 34: 516–527
Conclusions
• Most Trauma and ER literature incorrectly
identifies intraperitoneal blood as anechoic
– One hypothesis for this is that the time between
trauma and ultrasound is sufficient enough for the clot
to begin to separate
• Secondary exam is more sensitive because the
separation of plasma and clot not more bleeding
• Because most exams do correctly identify old
clot, the FAST exam is still a useful tool for
diagnosing bleeding if a sufficient time has
passed since injury