Ultrasound has emerged as a sensitive and reliable tool to evaluate patients presenting to the emergency department with acute and sub-acute thoracoabdominal trauma and hypotension.^1-3

Focused bedside ultrasound can accurately detect fluid in the peritoneal and pleural cavities and air in the pleural cavity, and it is more reliable than physical examination.⁴

Furthermore, use of bedside ultrasound in thoracoabdominal trauma expedites time to definitive care, because it can help determine whether an emergent intervention such as chest tube thoracostomy or trauma consultation and surgery are required.⁵

How to Perform the EFAST

• Positioning. Most patients presenting with thoracoabdominal trauma will be positioned supine with the c-spine immobilized. Placing patients in the Trendelenburg position increases the sensitivity of the abdominal FAST examination.⁶
• Probe. A low-frequency probe is utilized for better penetration of tissues in the abdominal cavity. A high-frequency probe is preferred by some operators to evaluate the thoracic cavity because it provides better resolution and detail of the pleura. However, the low-frequency probe can be used to expedite completion of the examination.

Scanning the Anterior Lung

Place the probe in the second or third intercostal space in the mid-clavicular line in a sagittal orientation, and slide the probe caudally for evaluation of a pneumothorax (see image 1).

The upper rib/pleural line/lower rib profile has the appearance of a bat flying out of the screen and is referred to as the bat sign.

At the inferior edge of the thoracic cage, slide the probe laterally at the level of the 6th intercostal space in the anterior axillary line. Normal lung findings include visible sliding at the level of the pleura in B-mode and comet tails (see image 2).

Comet tails are vertical reverberation artifacts arising from the pleural line. Lung sliding and the presence of comet tails are evidence of movement of the visceral on the parietal pleura. In M-mode, this normal lung sliding pattern is casually called the seashore sign⁷ (see image 3). Lung findings suggestive of a pneumothorax include the loss of pleural sliding, as there is loss of contact between the visceral and the parietal pleura.

A distinct pattern on M-mode commonly called the stratosphere sign will be present⁷ (see image 4). Some call this the bar code sign. Lung sliding may be absent in patients who are not spontaneously breathing, even in the absence of pneumothorax. If no lung sliding is present, the heartbeat may be visualized as pulsations of the expanded lung corresponding to the heart rate. This finding, referred to as the lung pulse, is equivalent to lung sliding.⁸ The lung point is the transition between collapsed and normally expanded lung. Although difficult to locate, the lung point is reportedly 100% specific for pneumothorax when present.⁹

Scanning the Pericardial Space

Place the probe in the subxiphoid space with the probe marker to the right and right of midline. Utilize the liver as an acoustic window. The angle of the probe with the skin may be as shallow as 5-10 degrees. The patient’s inherent respiratory pattern will bring the heart closer to and farther from the probe.

Adjust the depth to allow visualization of the posterior bright white pericardium. A black stripe of fluid separating the hyperechoic pericardium from the gray myocardium is concerning for a traumatic pericardial effusion (see image 5).

Scanning the Hepatorenal Space

Place the probe in the anterior axillary line at the inferior portion of the thoracic cage with the probe marker pointed toward the head in a coronal plane. Scan cephalad and caudad in this or the mid-axillary line until the clear interface of the liver and kidney are viewed (see image 6). To image the inferior pole of the right kidney, rotate the probe obliquely, as this approximates the normal anatomic lie of the organ. Intraperitoneal fluid appears as a black hypoechoic or anechoic stripe in the hepatorenal interspace (see image 7).

Scanning the Splenorenal Space

Place the probe in the mid or posterior axillary line at the inferior portion of the thoracic cage, with the probe marker pointed toward the head in the coronal plane.

Note that the left kidney is anatomically positioned more superior than the right kidney; for this reason, the probe is positioned more cephalad to view the interface. Scan cephalad and caudad in this or the mid-axillary line until the clear interface of the spleen and kidney is viewed.

To image the inferior pole of the left kidney, rotate the probe obliquely, because this approximates the anatomic lie of the organ. Intraperitoneal fluid appears as a black hypoechoic stripe in the splenorenal interspace (see image 8).

Scanning the Pleural Spaces

Using the same probe in the same position as for evaluation of the hepatorenal and splenorenal spaces, slide the probe cephalad one rib space for evaluation of the area above the diaphragm.

The presence of mirror imaging of the liver or spleen above the hyperechoic line representing the hemidiaphragm is evidence against pleural fluid (see image 9). If this area appears black or anechoic, there should be concern for pleural fluid proximal to the dia-phragm (see image 10). For the right pleural space, the probe would be located in the anterior axillary line between the sixth and ninth intercostal spaces. If a rib shadow precludes the ability to evaluate this area, rotate the probe obliquely toward the back.

For the left pleural space, the probe would be located in the posterior axillary line between the fourth and eighth intercostal spaces. Again, rotate the probe toward the back if rib shadows prevent full evaluation.

Scanning the Rectovesicular Space

This space should be evaluated in both the longitudinal and transverse planes. Ideally, the bladder will be full enough to act as an acoustic window to the space behind the bladder. Place the probe above the pubic bone with the probe marker pointing to the patient’s right side, and evaluate for free fluid (an area of hypoecho-genicity) in the anterior vesicouterine space and the posterior rectouterine space (see image 11). Rotate the probe 90 degrees clockwise so that the probe marker points toward the head for evaluation in the longitudinal plane.

Repeating the EFAST

A negative EFAST does not exclude entirely the presence of thoracoabdominal injury. Small amounts of free fluid and small pneumothoraces may not be visible on an initial EFAST. Patients with stable vital signs and a concerning history should be observed for at least 4 hours and have the EFAST repeated. Repeat EFAST should be performed sooner if a patient’s clinical picture is deteriorating and vital signs become unstable.

Conclusion

Pitfalls include:

• Overreliance on ultrasound: Ultrasound cannot evaluate the retroperitoneum and cannot distinguish solid organ injury.
• Delaying transport to operating room: When immediate surgical intervention is clearly indicated (e.g., eviscerating injury), skip the EFAST.
• Failing to scan the inferior pole of the kidney: Free fluid will first accumulate close to the inferior pole of the kidneys.
• Failing to recognize clotted blood: Patients with delayed presentations after thoracoabdominal trauma may not have classic sonographic findings. Clotted blood has variable echogenicity.
• Failure to understand other limitations of EFAST: Morbidly obese patients and those with massive subcutaneous emphysema are challenging to image with ultrasound. Also, EFAST cannot distinguish fluid type and cannot differentiate ascites from blood.

For best results, repeat the ultrasound procedure in patients who deteriorate and before discharge of stable patients. Consider using the low-frequency probe for imaging of the thoracic cavity to decrease the length of time required for this examination.

Always place the patient in the Trendelenburg position to increase the sensitivity of the examination.

In summary, ultrasound is a useful diagnostic tool in the evaluation of patients with thoracoabdominal trauma. The use of EFAST can decrease time to definitive care and length of stay in the emergency department.

The EFAST can be performed by the emergency physician as a noninvasive bedside tool to detect the presence of pneumothorax, hemothorax, and intraperitoneal hemorrhage.

References

1. Soyuncu S., et al. Accuracy of physical and ultrasonographic examinations by emergency physicians for the early diagnosis of intra-abdominal haemorrhage in blunt abdominal trauma. Injury 2007;38:564-9.
2. Neri L., Storti E., and Lichtenstein D. Toward an ultrasound curriculum for critical care medicine. Crit. Care Med. 2007;35(5 Suppl):S290-304.
3. Blaivas M., Lyon M., and Duggal S. A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. Acad. Emerg. Med. 2005;12:844-9.
4. Rothlin M.A., et al. Ultrasound in blunt abdominal and thoracic trauma. J. Trauma. 1993;34:488-95.
5. Melniker L.A., 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. Ann. Emerg. Med. 2006;48:227-35.
6. Abrams B.J., et al. Ultrasound for the detection of intraperitoneal fluid: the role of Trendelenburg positioning. Am. J. Emerg. Med. 1999;17:117-20.
7. Lichtenstein D.A. Ultrasound in the management of thoracic disease. Crit. Care Med. 2007;35(5 Suppl):S250-61.
8. Lichtenstein D.A. General ultrasound in the critically ill. 2005, Berlin; New York: Springer. ix, 199 p.
9. Lichtenstein D., et al. The “lung point”: an ultrasound sign specific to pneumothorax. Intensive Care Med. 2000;26:1434-40.