Trauma Fast Exam

Focused Abdominal Sonography for Trauma (FAST)

Introduction (Trauma.org)

The use of focused ultrasonography has now become an extension of the physical examination of the trauma patient. Performed in the trauma room by properly trained and credentialed staff, it allows the timely diagnosis of potentially life-threatening hemorrhage and is a decision-making tool to help determine the need for transfer to the operating room, CT scanner or angiography suite.

“The most important preoperative objective in the management of the patient with abdominal trauma is to ascertain whether or not a laparotomy is needed, and
not the diagnosis of specific injury” – Polk 1983

Blunt Abdominal Trauma

Blunt abdominal trauma is a leading cause of morbidity and mortality among all age groups. Identification of serious intra-abdominal pathology is often challenging; many injuries may not manifest during the initial assessment and treatment period.

Ultrasound in Trauma (Focused assessment with sonography for trauma (FAST))

The aim is to identify life-threatening intra-abdominal bleeding or cardiac tamponade with a view to expediting definitive surgical management. It does not aim to exclude abdominal or thoracic injury.

  1. It helps to detect haemoperitoneum and haemopericardium.
  2. The primary benefit is to rapidly direct appropriate operative interventions in unstable
    patients.
  3. It is useful in both blunt and penetrating abdominal trauma.
  4. A high specificity means a positive FAST indicates an intra-abdominal injury.
  5. Moderate sensitivity means a negative FAST (apparent absence of free fluid) does not exclude significant injury.
  6. FAST alters the management of trauma patients, such that
    1. there is more rapid disposition to the operating theatre,
    2. it indicates a more rapid search for other causes of hypotension when negative,
    3. it reduces the number of computed tomography (CT) scans and diagnostic peritoneal lavage examinations (DPLs) performed and
    4. it is associated with shorter hospitalizations, less complications and lower charges.
  7. At this stage, however, there is little conclusive evidence that its use improves patient
    survival.
  8. Extended FAST (EFAST) includes assessment of the thorax for haemothorax and pneumothorax.

Anatomical References

  1. The first is the intrathoracic abdomen, which is the portion of the upper abdomen that lies beneath the rib cage. Its contents include the diaphragm, liver, spleen, and stomach. The rib cage makes this area inaccessible for palpation and complete examination.
  2. The second is the pelvic abdomen, which is defined by the bony pelvis. Its contents include the urinary bladder, urethra, rectum, small intestine, and in females, the ovaries, fallopian tubes, and uterus.
  3. The third is the retroperitoneal abdomen, which contains the kidneys, ureters, pancreas, abdominal aorta, and inferior vena cava.
  4. The fourth is the true abdomen, which contains the small and large intestines, the uterus (if gravid), and the bladder (when distended).

FAST Anatomy

Peritoneal and Retroperitoneal Anatomy

Anatomical Description of main pelvic arteries and veinsmalebladder

Fast Exam Anatomical Reference

Ultrasound in Trauma (Focused assessment with sonography for trauma (FAST) – Indications and role of FAST in penetrating trauma)

The aim of FAST in penetrating trauma is to determine whether one or more of the abdominal, pericardial or pleural cavities has blood in it. This indicates breach in the integrity of the cavity and potentially significant injury. Lack of free fluid in the abdomen does not exclude significant injury, as penetrating bowel injury is frequently not associated with free abdominal fluid.

  1. Unstable patient with multiple wounds
    1. It helps to locate and quantify bleeding and direct initial therapeutic measures.
  2. Unstable patients with a single penetrating thoraco-abdominal wound of uncertain trajectory
    1. To locate and quantify bleeding and direct initial therapeutic measures.
  3. Stable patient with one or more penetrating wounds
    1. When it is not certain whether immediate surgery is required
    2. To locate and quantify bleeding and direct therapeutic measures.

Other imaging and/or surgical exploration is generally required to exclude significant injury.

Mount Sinai Emergency Medicine Ultrasound

Focused Questions:

  1. Is there fluid in the peritoneal cavity?
  2. Is there a pericardial effusion?
  3. Is there fluid in the thorax (ie. hemoperitoneum)?
  4. Is there a pneumothorax? (see separate pneumothorax tutorial)

UCSF-East Bay Trauma Service – FAST Exam

Rational

Focused Abdominal Sonography for Trauma (FAST) allows rapid and noninvasive determination of the presence of free intra-abdominal fluid.  In patients sustaining blunt truncal trauma who are in shock, this information will allow the clinician to forego other diagnostic tests and quickly transfer the patient to the operating room for emergency celiotomy and control of intra-abdominal hemorrhage.  The use of FAST has all but supplanted the diagnostic peritoneal lavage (DPL) in the evaluation of unstable patients after blunt truncal trauma.

Technique The FAST exam is performed as part of the initial evaluation of the trauma patient in the emergency center.  It consists of four separate views of four anatomic areas (see diagrams below):

  1. The right upper abdomen (Morison’s space between liver and right kidney)
  2. The left upper abdomen (perisplenic and left perirenal areas)
  3. Suprapubic region (perivesical area)
  4. Subxyphoid region (pericardium)

above: diagram of the RUQ and Morison’s space

Excerpts From Dr. Geoffrey Hayden Notes (Trauma Ultrasound and the FAST exam):

Pericardial view:

Description:

  1. Look at the interface between the right ventricle and the liver to identify pericardial fluid
  2. Cardiac tamponade identification is the immediate aim of this study
  3. A little fluid (non-circumferential) may be completely normal
  4. Circumferential pericardial fluid +/- RV or RA collapse is concerning

Sono technique:

  1. Probe in the subxiphoid area and angled toward the patient’s left shoulder, with the pointer at 9 o’clock
  2. Transducer is almost parallel to the skin of the torso
  3. Press firmly just inferior to the xiphoid
  4. May need to move the transducer further to the patient’s right in order to use the liver as an acoustic window
  5. Normal pericardium is seen as a hyperechoic (white) line surrounding the heart

Pitfalls:

  1. A pericardial fat pad can be hypoechoic or contain gray-level echoes; almost always located anterior to the right ventricle and is not present posterior to the left ventricle
  2. Small pericardial fluid (non-circumferential) may be normal; do not immediately ascribe hypotension to a small amount of pericardial fluid
  3. Scan may be limited by obesity, protuberant abdomen, abdominal tenderness, gas, as well as pneumoperitoneum/pneumothoraces
  4. Sometimes hard to differentiate pleural fluid versus pericardial fluid

Pearls:

  1. Transducer should be flat to the skin (overhand technique with probe)
  2. Have the patient take a breath in and “hold it”
  3. If the subxiphoid window is not available, may substitute with the parasternal long or short axis; know your alternatives

Perihepatic view (RUQ):

Description:

  1. Evaluating Morison’s pouch=potential space between the liver and the right kidney
  2. 4 areas to evaluate for “free fluid”:
    1. Pleural space
    2. Sub-diaphragmatic space
    3. Morison’s pouch
    4. Inferior pole of the kidney/paracolic gutter

Sono technique:

  1. Probe indicator in the subcostal window points cranially (stay midclavicular, fluid is dependent)
  2. Probe indicator in the intercostal window should point toward the right posterior axilla along the angle of the ribs (oblique angle)
  3. Right intercostal oblique and right coronal views: evaluate for right pleural effusion, free fluid in Morison’s pouch, and free fluid in the right paracolic gutter
  4. The paracolic gutter may be visualized by obtained by placing the transducer in either the upper quadrant in a coronal plane and then sliding it caudally from the inferior pole of the kidney
  5. The liver appears homogenous, with medium-level echogenicity; Glissen’s capsule is echogenic
  6. The kidneys have a brightly echogenic surface (Gerota’s fascia)

Pitfalls:

  1. Perinephric fat is a mimic for hematoma
  2. Duodenal fluid, the gallbladder, and the IVC are all mimics for free fluid (follow these carefully)

Pearls:

  1. Perinephric fat has even thickness (not pointy), and is symmetric with the opposite kidney
  2. Pleural fluid will present as an anechoic strip superior to the diaphragm, instead of the usual “mirror artifact”

Perisplenic view (LUQ):

Description:

  1. 4 areas to evaluate for “free fluid”:
    1. Pleural space
    2. Sub-diaphragmatic space
    3. Splenorenal recess
    4. Inferior pole of the kidney/paracolic gutter

Sono technique:

  1. Reach across the patient
  2. Probe indicator should point toward the left posterior axilla along the angle of the ribs (oblique angle, pointer toward 2 o’clock)
  3. Think more posterior and more cephalad than would be expected
  4. The left intercostal oblique and left coronal views may be used to examine for left pleural effusion, free fluid in the subphrenic space and splenorenal recess, and free fluid in the left paracolic gutter
  5. The spleen has a homogenous cortex and echogenic capsule and hilum

Pitfalls:

  1. Fluid-filled stomach can mimic fluid, as can loops of bowel and perinephric fat (see above)

Pearls:

  1. Posterior posterior posterior
  2. Angle probe with ribs

Pelvic view:

Description:

  1. Evaluating for free fluid around the bladder
  2. Most dependent part of the abdomen (though RUQ is still the most sensitive for FF)

Sono technique:

  1. Probe should be placed 2cm superior to the symphysis pubis along the midline of the abdomen
  2. Both transverse and longitudinal images should be obtained
  3. Angle probe down until the prostate or vaginal stripe is identified (any lower and you will be inferior to the peritoneal reflection)
  4. Sweep all planes of the bladder
  5. In the longitudinal plane, scan side to side to identify pockets of free fluid between bowel loops

Pitfalls:

  1. Fluid within a collapsed bladder or an ovarian cyst may appear as free intraperitoneal fluid
  2. Seminal vesicles may also be incorrectly identified as free fluid
  3. Premenopausal females may normally have a small amount of free fluid in the pouch of Douglas
  4. Watch out for gain artifact; turn your gain down for this exam
  5. The iliopsoas muscles can mimic free fluid (they look like kidneys)

Pearls:

  1. A full bladder is essential for an adequate scan (can’t do much about this with sick trauma patients)

Pneumothorax study:

Description:

  1. Evaluating for a pneumothorax
  2. Absence of a “sliding sign” and comet tail artifact supports the diagnosis

Sono technique:

  1. The pleural space is just deep to the posterior aspect of the ribs
  2. There is a notable echogenic line with a “sliding appearance” composed of the visceral and parietal pleura
  3. This is considered the normal “sliding sign” and is considered negative for pneumothorax
  4. May use a high-frequency, linear transducer or your abdominal probe
  5. The transducer is placed longitudinally (pointed cranially) in the midclavicular line over the third or fourth intercostal space
  6. The transducer is then moved inferiorly in a systematic fashion, ensuring an appropriate “sliding sign”

Pitfalls:

  1. Bilateral pneumothoraces may limit your comparison of sides
  2. Any movement of the probe may give you a false negative study (see pleural sliding when there isn’t…..)

Pearls:

  1. The abdominal probe is a reasonable alternative to the linear probe for the pneumothorax study; it may make the “sliding sign” easier to visualize
  2. Systematic scanning from cranial to caudal

Keys to the FAST exam:

  1. Complete exam in every view
  2. Identify pathology, not VIEWS
  3. All abnormalities should be imaged in 2 orthogonal planes
  4. Note incidental findings

Limitations to the FAST exam:

  1. Though the quantity of free intraperitoneal fluid that can be accurately detected on ultrasound has been reported as little as 100mL, the typical cut-off is around 500-600mL; smaller amounts of free fluid may be missed (one reason why a repeated exam can be helpful)
  2. Can’t detect a viscus perforation
  3. Can’t detect a bowel wall contusion
  4. Can’t detect pancreatic trauma
  5. Can’t detect renal pedicle injuries

Points to Consider

  1. Pelvis – most dependent
  2. Hepatorenal fossa – most dependent area in the supramesocolic region
  3. Pelvis and Supramesocolic Areas communicate – Phrenicolic ligament prevents flow
  4. Liver/Spleen Injuries – represents about 2/3 of cases of blunt abdominal trauma
  5. Intraperitoneal Fluid may consist of
    1. Blood
      1. Fresh Blood
        1. Anechoic (black)
      2. Coagulated Blood
        1. Hypoechoic
    2. Preexisting ascites
    3. Urine
    4. Intestinal contents
  6. Mimics of fluid in RUQ
    1. Perinephric fat
      1. May be hypoechoic like blood
      2. Usually evenly layered along kidney
      3. If in doubt, compare it to the left kidney
    2. Abdominal Inflamation
      1. Widened extra-renal space
      2. Echogenicity of kidney becomes more like the liver parenchyma
  7. LUQ (near ribs 9 and 10)
    1. Acoustic window (spleen) is smaller than the liver
    2. Mild inspiration will optimize image
    3. Bowel interference is common
  8. Pelvis (suprapubic)
    1. Helpful to image before placement of a Foley catheter
    2. If bladder is empty or Foley already placed
      1. Place an IV bag on the abdomen and scan through the bag
    3. A very large bladder can displace fluid from the pouch of Douglas
      (cul-de-sac) in females and cause a false-negative study
  9. Increased sensitivity with
    1. increased number of views
    2. Trendelenberg
    3. Serial Examinations
  10. Normal echo does not definitively rule out major pericardial injury
  11. Epicardial fat pad may easily be misinterpreted as a clot

SonoSite (Videos)

FAST RUQ Exam: Normal Exam (Hepatorenal)

FAST RUQ Exam: Hemorrhage (Hepatorenal)

FAST LUQ Exam: Normal and Abnormal (Splenorenal or Perisplenic)

FAST Suprapubic Exam: Normal (Bladder or Pelvic)

HQMedEd

Mike Stone

  1. FAST Bonus – RUQ Exam Technique
  2. FAST Bonus – LUQ Exam Technique
  3. FAST Bonus – Subcostal Exam Technique
  4. FAST Bonus – Pelvis Technique

Series

  1. FAST Part 2 – Getting the Right Upper Quadrant Right…
  2. FAST Part 3 – Heidi Kimberly Does the Left Upper Quadrant
  3. FAST Part 4 – The Pelvic View
  4. FAST Part 5 – Pneumothorax (E-FAST)
  5. FAST Part 6 – Josh Rempell covers hemothorax and reviews pneumothorax

Flow Diagrams

Schwartz’s Principles of Surgery

Fast Exam Chart

Wikipedia – Interpretation

File:FAST Algorithm.svg

Other

Penetrating Thoracoabdominal Trauma

Blunt Abdominal Trauma

Summary of FAST vs. CT vs. DPL (Diagnostic Peritoneal Lavage)

  1. Speed – FAST>DPL>CT
  2. Sensitivity – DPL>CT and FAST
  3. Specificity – CT>FAST>DPL
  4. Localization – CT>FAST>DPL
  5. Ease/portability – FAST>DPL>CT
  6. Safety – FAST>CT>DPL
  7. Cost – DPL<FAST<CT

References

  1. Anechoic Stripe Size Influences Accuracy of FAST Examination Interpretation
  2. Deep Impact of Ultrasound in the Intensive Care Unit – The “ICU-sound” Protocol
  3. Diagnostic accuracy of surgeon-performed focused abdominal sonography (FAST) in blunt paediatric trauma
  4. Emergency ultrasound-based algorithms for diagnosing blunt abdominal trauma
  5. EAST – Evaluation of Blunt Abdominal Trauma
  6. eMedicine
    1. Bedside Ultrasonography for Pneumothorax
    2. Focused Assessment With Sonography for Trauma (FAST): Slideshow
    3. Focused Assessment with Sonography in Trauma (FAST)
    4. Imaging in Kidney Trauma
    5. Pneumothorax
    6. Intra-abdominal injuries in polytrauma
  7. FAST scan – Is it worth doing in hemodynamically stable blunt trauma patients
  8. Focused abdominal sonogram for trauma – the learning curve of nonradiologist clinicians in detecting hemoperitoneum
  9. Focused Assessment with Sonography for Trauma (FAST): results from an international consensus conference
  10. Pediatric Abdominal Trauma Imaging
  11. Penetrating stab wounds to the abdomen: use of serial US and contrast-enhanced CT in stable patients
  12. Prospective analysis of the effect of physician experience with the FAST examination in reducing the use of CT scans
  13. Role of ultrasonography in penetrating abdominal trauma: a prospective clinical study
  14. The technical errors of physicians learning to perform focused assessment with sonography in trauma
  15. Test Characteristics of Focused Assessment of Sonography for Trauma for Clinically Significant Abdominal Free Fluid in Pediatric Blunt Abdominal Trauma
  16. The ultrasound screen for penetrating truncal trauma
  17. Ultrasound detection of blunt urological trauma: a 6-year study
  18. Ultrasound in Abdominal Trauma
  19. Ultrasound in Trauma
  20. Use of focused abdominal sonography for trauma at pediatric and adult trauma centers – a survey
  21. Validation of nurse-performed FAST ultrasound
  22. What is the utility of the Focused Assessment with Sonography in Trauma (FAST) exam in penetrating torso trauma

3 thoughts on “Trauma Fast Exam

  1. Pingback: SonoStudy: False negative FAST scans: association with patient characteristics/injuries/outcomes? | SonoSpot: Topics in Bedside Ultrasound

  2. Pingback: SonoTips & Tricks: The upper quadrants of the FAST scan #FOAMed | SonoSpot: Topics in Bedside Ultrasound

  3. Pingback: Fluid Management | Welcome to Jeremy Jaramillo's Blog

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