Ultrasound of the Abdomen – eFAST

Extended Focused Assessment with Sonography for Trauma (eFAST)

By Nicholas Gowing

Specialist, Dep of Anesthesia and Intensive Care, Sahlgrenska University Hospital, Göteborg, Sweden.

The eFAST is an ultrasound examination of the abdomen and thorax (extended) useful for guiding treatment in the trauma patients when a CT scan is yet not performed (eg prehospital) or considered inappropriate (severely injured patients requiring immediate operative care). In practised hands, the eFAST can give reliable (yes/no) findings for the following conditions:

  • Pneumothorax
  • Pleural effusion
  • Intraperitoneal free fluid
  • Pericardial effusion

The volume of free fluid is not clearly linked to severity and should be interpreted based on the clinical context. The exam should ideally be performed without interrupting clinical care, typically simultaneous with the primary survey.

We suggest using the abdominal probe (otherwise known as Curvilinear or Curved Array Probe) for the entire eFAST examination, though in certain patients it may be necessary to use the phased array probe for satisfactory cardiac views. The probe marker should always be oriented cranially when scanning in the longitudinal plane or on the patients’ right side when scanning in a transverse plane. By convention, the indicator marker should be placed on the left side of the screen.

The following views make up the eFAST, green signifying the traditional FAST views, with red signifying the EXTENDED views.


The Anterior Lung View

The Anterior Lung View (right & left) are used for detection of pneumothorax and should be performed in the least dependent area of the chest. In the supine patient this will correspond to the 2nd – 4th intercostal spaces in the mid-clavicular line. Place the probe longitudinally on the chest with the probe marker aimed cranially. This will give a typical ‘bat-sign’ image, with two ribs and the pleural line in between them. Look for all of the typical artefacts of lung ultrasound: Lung sliding, Lung pulse, A-lines and B-lines. We are trying to identify the presence of air between the visceral and parietal pleura.

For more detailed description of lung ultrasound, please see “The Anaesthesia Practice Guide – Ultrasound of Thorax and Lungs”.

Picture below is showing two underlying ribs and the pleura line between them with a “Bat Sign”.

Pneumothorax is suggested by the absence of lung sliding, B-lines and lung pulse. The presence of a ‘lung point’ (the junction between sliding lung and absent sliding) confirms a pneumothorax with near 100% specificity, whilst presence of B-lines rule out a pneumothorax at the point of scanning. We do not recommend the use of M-mode scanning in the trauma setting.

Always consider the common causes of false positive pneumothorax when scanning

  • Bronchial intubation
  • Apnoea
  • Pleurodesis

The Pleural Views

The Pleural Views (right & left) are used for detection of pleural effusion (typically haemothorax in the trauma setting) and should be performed at the inferior portion of the thoracic cage in the posterior axillary line. eFAST examination of the pleural spaces can be thought of as ultrasonography of the diaphragm.

Place the probe with the marker aimed cranially and scan cephalad and caudad until the interface of the lung and liver- (right) or spleen- (left) is found. Identification of the diaphragm in between these structures is crucial in determining the location of any free fluid found during the examination. Slide the probe cephalad one rib space and tilt the probe parallel with the ribs to best evaluate the area above the diaphragm.

The presence of lung artefacts or ‘mirror imaging’ of the liver or spleen immediately above the diaphragm are evidence against pleural fluid. Any black or anechoic area is suggestive of pleural effusion. Further evidence of an effusion includes the presence of the ‘spine sign’, where the vertebral bodies are visible in the most distant portion of the screen. This is not typically seen unless there is a fluid collection.

Figure 1. Normal lung: Note the pleura and a lung artefact directly adjacent to the diaphragm.

Figure 2. Pleural effusion. Anechoic fluid above the diaphragm (dark area, collapsed lung also visualized within the effusion)


The RUQ/Hepatorenal View

The RUQ/Hepatorenal View is used for detection of free fluid within the peritoneum, specifically around the liver and within the hepatorenal recess (or Morison’s pouch). The position is very much like the one used for the R pleural space – longitudinal with the probe marker aimed cranially – but slightly more caudal and to the mid axillary line. As with the pleural views, once the liver and kidney have been identified, slightly rotate the probe parallel to the ribs in order to avoid bony artefacts. Fan through the liver to exclude free fluid, it may be necessary to slide down a rib space to examine the inferior pole of the liver. There are 3 distinct components to examining this window, corresponding to 3 potential spaces for fluid collection, each of which must be examined carefully:

  • Between the diaphragm and the liver
  • The hepatorenal recess
  • The inferior pole of the liver

Normal examination of the RUQ showing the 3 mandatory views.

Free fluid will appear black/anechoic, typically with sharp edges indicating fluid within a recess (as opposed to rounded edges such as blood vessels, gallbladder).

Free fluid below the diaphragm (there is also a pleural effusion).

Free fluid around the inferior pole of the liver.


The LUQ View

Unlike the RUQ, free fluid in the LUQ collects circumferentially around the spleen and not necessarily adjacent to the left kidney. The focus of the examination is therefore below the diaphragm and around the spleen in its entirety. The position of the probe is also slightly different to the opposite side, with a slightly more cephalad position in the posterior axillary line. In order to examine the supine patient, the examiners’ knuckles will typically need to rest against the bed/stretcher. Avoiding the full stomach is commonly difficult in the trauma patient, requiring an even more exaggerated posterior view to satisfactorily visualise the spleen.

Normal LUC view

Free fluid beneath the diaphragm and surrounding the spleen


The Pelvic View

The Pelvic View uses the bladder as an ‘acoustic window’ and we aim to determine if there is free fluid between the bowel, bladder or other pelvic organs. A full bladder is therefore highly desirable. If a urinary catheter is inserted immediately prior to the examination, it should be clamped until the eFAST is completed. Begin with the probe immediately cephalad to the pubic symphysis and scan inferiorly towards the pelvis from the midline in both a longitudinal and transverse manner.

In females a small amount of fluid is physiological, whilst in makes the seminal vesicles are hypoechoic and must not be mistaken for free fluid.

Normal pelvic views transverse & longitudinal. Note the prostate. The uterus will occupy a similar position in females.

Free fluid in the pelvis in both views.


The Subcostal View

The Subcostal View is used for identifying pericardial effusion. Place the probe in a transverse position immediately below and to the patients’ right of the xiphoid process. This view uses the liver as an ‘acoustic window’ and it may be necessary to slide the probe further to the patients’ right side in order to look ‘through’ the liver and attain a satisfactory view. In practice it is often easiest to start with the probe lying flat on the patients’ abdomen. The eventual angle to skin for a good image can often be as shallow as 5-10 degrees.

We are looking for signs of pericardial effusion. Cardiac Tamponade is a clinical diagnosis that cannot be made with an eFAST examination alone. Both the anterior and posterior pericardium must be visualised to confirm a negative examination. Always consider pleural effusion if fluid is only visualised in the far field. Another common cause of a false positive scan is the presence of epicardial fat, which appears hypoechoic but not anechoic.

Normal view, please note anterior & posterior pericardium

Pericardial effusion, dark areas.

Author:

Dr Nicholas Gowing

Specialist, Dep of Anesthesia and Intensive Care, Sahlgrenska University Hospital, Göteborg, Sweden.