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Clinical Procedures > Radiology
Bedside Ultrasonography, Trauma Evaluation
Article Last Updated: Jun 5, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 13  
Author: Timothy Jang, MD, Director of Emergency Ultrasound, Olive View-UCLA Medical Center, Clinical Faculty, Division of Emergency Medicine, Washington University School of Medicine
Editors: James Quan-Yu Hwang, MD, Attending Physician, Department of Emergency Medicine, Brigham & Women's Hospital; Clinical Instructor, Harvard Medical School; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine; Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Author and Editor Disclosure
Synonyms and related keywords:
ultrasound, trauma ultrasound, diagnostic ultrasound, sonography, blunt abdominal trauma, BAT, bedside ultrasound, FAST, FAST exam, focused abdominal sonography for trauma, focused abdominal sonography trauma, bedside ultrasonography, diagnostic peritoneal lavage, DPL, abdominal CT, intra-abdominal injury, E-FAST, extended FAST, acute abdominal injury, blunt abdominal injury, hemoperitoneum, hemothorax, pneumothorax, penetrating trauma, abdominal trauma, intraperitoneal free fluid, Morison pouch, Douglas pouch, perisplenic view, parasternal long-axis, subxiphoid long-axis
Blunt abdominal trauma (BAT) is a common reason that patients present to the emergency department. Unfortunately, patient history and physical examination often lack the necessary sensitivity and specificity to accurately diagnose acute traumatic pathology. Diagnostic peritoneal lavage (DPL) was historically used to determine which patients needed exploratory laparotomy, but DPL is difficult to perform in pregnant patients, cannot be used for serial assessment, and is overly sensitive, which leads to a high negative laparotomy rate.1 Abdominal CT has better specificity than DPL for intra-abdominal injury in BAT but can be difficult to perform in hemodynamically unstable patients, is expensive, requires removing patients from the clinical arena, and may be relatively contraindicated in pregnant patients.2
The focused assessment with sonography for trauma (FAST) examination, on the other hand, is an important and valuable diagnostic alternative to DPL and CT that can often facilitate a timely diagnosis for patients with BAT.3, 4, 5
The benefits of the FAST examination include the following:
- Decreases the time to diagnosis for acute abdominal injury in BAT
- Helps accurately diagnose hemoperitoneum
- Helps assess the degree of hemoperitoneum in BAT
- Is noninvasive
- Can be integrated into the primary or secondary survey and can be performed quickly, without removing patients from the clinical arena
- Can be repeated for serial examinations
- Is safe in pregnant patients and children, as it requires less radiation than CT
- Leads to fewer DPLs; in the proper clinical setting, can lead to fewer CT scans (patients admitted to the trauma service and to receive serial abdominal examinations)6
An extended version of the standard FAST examination (E-FAST) has been established and offers additional information. In addition to imaging of the abdomen, the E-FAST examination includes views of bilateral hemithoraces to assess for hemothorax and of bilateral upper anterior chest wall to assess for pneumothorax.7 For the remainder of this article, the FAST examination is referred to as the E-FAST examination, as appropriate. For additional resources and education on trauma, visit Medscape’s Trauma Resource Center.
Indications for focused assessment with sonography for trauma (FAST) include the following: - Blunt abdominal trauma
- Stable penetrating trauma
- Assessment of the degree of intraperitoneal free fluid
- When emergent treatments such as intravenous fluids or transfusion of blood are indicated, performance of a focused assessment with sonography for trauma (FAST) examination should not delay the initiation of these treatments.
- Although ongoing resuscitation and extremis are not contraindications, the FAST examination can be difficult to perform in such situations.
- Anesthesia is generally not necessary for sonographic evaluation.
- Analgesics may be required for pain control secondary to the particular trauma.
- Ultrasound machine
- Ultrasound-conducting gel
- Patients should be evaluated in the supine position but can be moved to the Trendelenburg or lateral decubitus position for improved visualization of particular views.
- Male patients should have the entire abdomen exposed for the examination. Take care with female patients to minimize the exposure of sensitive areas.
Relevant anatomy
Blood tends to pool in dependent areas. The hepatorenal recess (Morison pouch) is the most dependent space in the supramesocolic region. The suprapubic view allows for the assessment of fluid in the most dependent area in the inframesocolic region. In women, this space (the rectouterine space) is known as the pouch of Douglas.
Components of examination
The focused assessment with sonography for trauma (FAST) examination should include views of (1) the hepatorenal recess (Morison pouch), (2) the perisplenic view, (3) the subxiphoid pericardial window, and (4) the suprapubic window (Douglas pouch). If an E-FAST examination is performed, views of (1) the bilateral hemithoraces and (2) the upper anterior chest wall should also be performed.
Technique
- To visualize the Morison pouch, the transducer-probe should be placed in the right upper quadrant or laterally along the thoracoabdominal junction. This placement uses the liver as an acoustic window and avoids interference from air-filled bowel. The probe should be moved toward the inferior margin of the liver to obtain improved images of the right kidney.
Probe placement for right upper quadrant laterally.
Right upper quadrant view. - In cases of acute hemoperitoneum, blood appears as an anechoic stripe in the recess.
Free fluid in Morison pouch. - To obtain the perisplenic view, the transducer-probe should be placed over the left flank, lateral to the spleen along the posterior axillary line. When placed in this position, the handle of the probe should nearly touch the gurney. This allows the spleen to be used as an acoustic window and avoids interference from air-filled bowel. The probe should then be moved superiorly (toward the thoracoabdominal junction) and inferiorly to assess for the presence of free-fluid above the spleen and along the spleen tip.
Probe placement for left upper quadrant laterally.
Left upper quadrant view. - Be sure to assess the hepatodiaphragmatic and splenodiaphragmatic spaces, as blood often accumulates in these areas. A common pitfall is to only scan through the hepatorenal and splenorenal spaces.
Blood in the splenodiaphragmatic recess. - To obtain the suprapubic view, the probe should be placed just above the pubic symphysis and directed inferiorly into the pelvis. This view is easier to obtain when the bladder is full and prior to the placement of a Foley catheter. Be sure to obtain both sagittal and transverse suprapubic views.
Suprapubic probe placement.
Suprapubic view. - For the subxiphoid view, the transducer-probe should be placed in the subxiphoid area and directed into the chest toward the left shoulder to view the diaphragm and heart. This view can be difficult to obtain if the patient is experiencing significant abdominal pain. It often requires pressing the probe into the abdomen and angling the probe so that it is nearly parallel to the skin. In such cases, it is helpful to place the palm over the top of the probe with the thumb on the indicator.
Subxiphoid probe placement.
Subxiphoid view that demonstrates traumatic tamponade. - If the patient is experiencing significant abdominal pain or is obese, consider switching to a parasternal long-axis view. The subxiphoid long-axis view is another view that can be used to assess for pericardial effusions. This view also allows for the assessment of IVC size and collapsibility.
- If an E-FAST examination is being performed to rule out pneumothorax, place a high-frequency linear probe (8-12 MHz) with the indicator toward the patient's head in a long-axis orientation. Place the probe high on the patient's chest, just below the clavicles in the midclavicular line. Look for the pleural line sitting at the back of the ribs. The presence of sliding between the visceral and parietal pleura indicates the lack of a pneumothorax in the area being scanned. The absence of sliding implies the presence of a pneumothorax.
- If rib shadowing is an obstacle, rotate the transducer-probe 30º to fit between the ribs. If available, consider switching to a probe with a smaller footprint (eg, phased array probe).
- If the desired recesses are difficult to visualize, ask the patient to take a slow, deep breath and, if possible, to hold it. This may move the recess into view.
- Be sure to fully interrogate each region by scanning through it in its entirety. A single negative view in each region does not constitute a negative E-FAST examination.
- Intraperitoneal free fluid may not be hemoperitoneum. Consider ascites, urine, peritoneal dialysate, and other etiologies of intraperitoneal fluid. Be aware of false positives from fatty tissue and attempt to determine precisely where visualized fluid is located.
- Hemoperitoneum may take time to accumulate. Maintain a low threshold for repeating the E-FAST examination, especially if the patient's vital signs or examination change. Serial E-FAST examinations increase the sensitivity for detecting intraperitoneal free fluid secondary to blunt abdominal trauma.
- The E-FAST examination is an excellent initial imaging modality in trauma to evaluate for the presence of hemothorax or pneumothorax. While it is quite specific, it is not sensitive enough to rule out all significant pathology.
- Typically, no complications are associated with this procedure.
The authors and editors of eMedicine gratefully acknowledge the assistance of Lars Grimm with the literature review and referencing for this article.
| Media file 1:
Probe placement for right upper quadrant laterally. |
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Probe placement for left upper quadrant laterally. |
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| Media file 10:
Subxiphoid view that demonstrates traumatic tamponade. |
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Bedside Ultrasonography, Trauma Evaluation excerpt Article Last Updated: Jun 5, 2008
Topic originally published: Jun 5, 2008
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