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Outline
• Sonography in trauma - FAST exam
Abdominal and Retroperitoneal
Sonography
– Indications
– Limitations
– Techinique
• Vascular Ultrasound – Aorta
Dana Sajed, MD
Massachusetts General Hospital
What Is It?
A limited ultrasound examination for the
detection of free fluid in the torso in the
setting of trauma or hypotension
Focused
Assessment with
Sonography in
Trauma
E-FAST
Extended FAST
Involves scanning to
detect:
• Pneumothorax
or
• Fluid in the thorax
Focused Questions
The FAST exam answers very specific questions:
1) Is there free fluid in the peritoneum?
2) Is there fluid in the pericardium?
3) Is there fluid in the thorax?
– Epidemiology
– Technique
– Clinical Protocol
Evaluation in Trauma
• CT: Non-invasive, gives detail about organs…
but is also expensive, not always available,
involves transport of potentially unstable pt
away from ER, ionizing radiation
• DPL: Very sensitive… invasive, uncomfortable
for pt, complications can be devastating
• US: Less sensitive… but specific, non-invasive,
can detect 250cc of free fluid, performed at
bedside
Limitations
• The FAST exam does NOT identify specific organ
lesions
• Poor test for detection of retroperitoneal bleeding
• Does not distinguish blood vs other types of fluidascites, bladder perforation, ruptured cyst
• Does not tell you the source of bleeding
• May be technically limited - obesity, post-op patients,
subcutaneous emphysema, etc…
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Advantages
• Performed rapidly at bedside
• Noninvasive
• Inexpensive
• Easily repeated
• Highly specific for therapeutic laparotomy in
blunt trauma
Indications for FAST Exam
• Blunt Abdominal Trauma
• Penetrating Cardiac Trauma – detect effusion,
tamponade
• Thoracic Trauma – PTX, HTX
• Penetrating Abdominal Trauma – less
sensitive for detecting need for laparotomy
• Polytrauma – may help prioritize management
• Mass casualties – Armenia 1988, Turkey 1999
• Undifferentiated Hypotension – E-FAST
Why FAST works
Four Views of the FAST Exam
Pericardium
Fluid pools in predicable locations in the
abdomen:
Subhepatic
Perisplenic
RUQ
Perinephric
Pelvic
LUQ
Pelvis
Subpleural
Anatomy: RUQ
RUQ
Probe placed around 8-11th rib space, mid-axillary line
R Kidney
Liver
(
Morison’s
Pouch
Fan probe to capture
retroperitoneal
structures
View Includes
Liver
Kidney – must
include inferior
pole!
Morison’s pouch
Diaphragm and
Lung (E-FAST)
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Liver
RUQ
RUQ
RUQ
RUQ
Optimizing the RUQ View
Optimizing the RUQ View
Morison’s
Pouch
Kidney
Diaphragm
Place pt in trendelenburg – fluid will flow
towards the potential space
Rib shadow
• May need to slide probe around rib
• Rotate probe obliquely to avoid shadow
• Have pt take deep breath and hold
If unable to obtain
adequate midaxillary view:
• Reposition probe
anteriorly
• Same image
obtained due to
large acoustic
window of liver
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Left Upper Quadrant
• Probe at left posterior
axillary line
• 6-9th rib space
• Examine for:
– Fluid in splenorenal
recess
– Fluid in
subdiaphragmatic
space
– Fluid in left pleural
space
LUQ
Splenocolic
Ligament
LUQ
LUQ
LUQ
LUQ
Spleen
Kidney
Diaphragm
Free Fluid
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LUQ
LUQ
Spleen
Kidney
The “gastric fluid” sign: an unrecognized false-positive finding during
focused assessment for trauma examinations. Nagdev A, Racht J. Am J
Emerg Med. 2008 Jun;26(5):630.e5-7
LUQ
Difficulty obtaining LUQ images
• The spleen is much smaller than the liver and
gives less of an acoustic window
• Bowel gas and stomach bubble may create
interference
LUQ
• Try angling the probe obliquely to sneak in
between the ribs
• Have the patient take a deep breath to lower
the diaphragm and bring spleen and kidney
below ribs
• Most common mistake is usually not starting
superior enough or posterior enough
• Rib shadows, obesity, etc.
Pelvis
In male, free
fluid seen
posterior to
the wall of
the bladder
Rectovesical space
Pelvis
Rectouterine
Pouch
(of Douglas)
Vesicouterine
Pouch
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Pelvis
• Ideally done before foley is placed or bladder
is emptied
• Two views to obtain
Transverse
Longitudinal (Sagittal)
• Probe is placed on symphisis pubis, aimed
caudad
Transverse Pelvis
Probe in the midline just cephalad to
the pubic bone
Probe indicator
pointed to pt’s
right
Pelvis
Bladder
Ovary
Pelvis
Free Fluid
Ovary
Uterus
Pelvis
Pelvis
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Pelvis
Pelvis
Longitudinal (Sagittal)
Suprapubic View
Longitudinal View
Probe in the midline
just cephalad to the
pubic bone
Aim towards feet
Sagittal Pelvis
Sagittal Pelvis
Sagittal Pelvis
Pelvis
Difficulty identifying the bladder:
Free Fluid
• Most often, the probe is too cephalad – bring the
probe almost on top of the symphysis pubis and
angle toward the feet
• If the bladder is empty- saline in through foley
catheter
• If no foley, give IV fluids
• Bladder may not be in midline – slide to obtain
images on the sides
Place pt in reverse trendelenburg
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Controversies and Future Directions
• Randomized trauma
patients to FAST
protocol vs. trauma
evaluations without
FAST
• FAST patients had
- More rapid time to OR
- Fewer CT scans
- Complications
- Decreased length of stay
- Fewer hospital charges
FAST in penetrating trauma
• Studies indicate about equal sensitivity for
detecting hemoperitoneum as in BAT
• High specificity
• Assessment for violation of abdominal wall
• Within minutes it allows clinicians to
concentrate efforts on a cardiac, chest and or
intraperitoneal injury
Controversies and Future Directions
FAST in penetrating trauma
• Despite high specificity, poor predictor of need
for laparotomy
• Unnecessary in the unstable patient with
penetrating trauma
• Can not evaluate bowel injuries, which are
common in pen. trauma
ABDOMINAL AORTA
Epidemiology - AAA
• 13th leading cause of death in USA
– 15,000 deaths per year
• 1-3% of deaths among males 65-85
Risk Factors
• Male
• Atherosclerosis
– One million in USA > 65 yo have a AAA
• 7:1 M:F
• 65-85% mortality overall
– Half of these never make it to the OR
• Mortality significantly reduced with screening
and elective repair
• Smoking
• Hypertension
• Age
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Signs and Symptoms
“There is no disease more
conducive to clinical humility
than aneurysm of the aorta.”
• Usually asymptomatic until they expand
or rupture
• Pain - low back, flank, abdominal, or
groin
– Classically sudden, severe
– Often associated with nausea, vomiting
William Osler, circa 1900
• Rupture - Shock, hypotension,
tachycardia, syncope, AMS,
cardiovascular collapse
Indications
• Suspected AAA
Bedside Ultrasound
• Fast and it saves lives
• Pulsatile abdominal mass
• Unexplained hypotension/ CV collapse
– Average time to diagnosis by bedside US =
5.4 min
– Average time to diagnosis by CT = 83 min
• Elderly Patient?
– Average time to OR for diagnosis by US = 12
min
– Unexplained back/flank pain
– Unexplained hematuria
– Average time to OR for diagnosis by CT= 90
*Plummer
min* et al Abstract presented at 1988 ACEP Scientific Assembly
Anatomy
Aneurysm
• 85% are inferior to the renal
arteries
• Can occur at the bifurcation, or
beyond bifurcation into common
iliacs
• Two main forms:
Fusiform
Saccular
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Views of the Aorta
• Transverse:
– Proximal
– Mid
– Distal
– Bifurcation
• Longitudinal
– Look infra-renal
Goals of Bedside Ultrasound
• Yes or No answer to two questions
– Is abdominal aorta > 3
cm
– Are iliac arteries > 1.5 cm
THIS IS WHAT YOU MUST KNOW
Technique
• Ideally,
want to use
curvilinear
(low
frequency)
probe
• Can use
phased
array probe
as well
Technique
• Obtain transverse and longitudinal
images along the entire course of
abdominal aorta
• Measure outer wall to outer wall in two
planes
• Use vertebral shadow as reference point
• Apply gentle, constant pressure to
remove bowel gas
Proximal Aorta
• Start
immediately
below the
xiphoid
process
• Identify the
vertebral
body
• Identify the
SMA
Splenic Vein
SMA
Ao
Vertebral Body
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Mid Aorta
• Slide probe to the
umbilicus
• Slide the probe
caudally in the
midline
• The aorta
follows the
curvature of
the spine, more
anterior
• Again identify
the aorta
anterior to the
Distal Ao and Bifurcation
• Then aim caudally
Ao
• Measure both the distal
aorta and the common
iliacs
Spine
Longitudinal
Aorta
Longitudinal Aorta
• Visualize
the aorta
in the long
axis
• Look
infrarenall
y
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• Aorta lies
more anterior
caudally; to
get true crosssection must
angle probe
• Calipers
should be at
90 degrees to
the vessel for
most accurate
measurement
Measuring the Longitudinal Aorta
• Cylinder tangent
effect can lead to
off-axis
measurement
• In sagittal plane pan through aorta
and measure
maximal diameter
• Remember to measure OUTER
WALL to OUTER WALL of the aorta
• This is done to not miss a false
lumen
Bifurcation – Iliac Aneurysm
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Questions Answered By Bedside
Ultrasound
• Is there an abdominal aortic aneurysm?
– Aorta >3cm
– Iliac >1.5cm
• Remember that 85% of aneurysms are
inferior to the renal artery
• Remember the longitudinal axis
Pitfalls
• No real contraindication - delaying
immediate surgical care
• Imaging errors – Scan through the
entire plane, so as not to miss saccular
aneurysm
• Patient factors – body habitus, bowel
gas – apply gentle compression
• Failure to image iliacs
AAA Clinical Protocol
Clinical Suspicion of AAA?
Aorta > 3 cm
No
AAA ruled out
OR Iliacs > 1.5 cm?
Yes
Hemodynamically unstable?
No
CT
Yes
To OR!
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