Read this tutorial on the use of point of care ultrasonography (POCUS) for Pediatric Focused Assessment with Sonography for Trauma. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.
Summarize the indications and role of the FAST in the evaluation of injured children
Describe the technique for performing the pediatric FAST
Identify anatomical views and landmarks necessary for a complete pediatric FAST
Accurately interpret each pediatric FAST anatomic view and corresponding landmarks
Describe the literature on the pediatric FAST
You receive an emergency medical services (EMS) notification that they are 2 minutes out from your ED with a 3-year-old boy who fell down a flight of 10 concrete stairs. He is awake and breathing spontaneously but irritable and crying with an obvious deformity to his right arm. EMS placed him in a cervical-collar and are bringing him to your ED.
Trauma remains the leading cause of childhood death and disability in children >1 year of age . While head and thoracic trauma account for most death and disability in children, missed abdominal injuries are a common cause of mortality . Particularly in polytrauma scenarios, it can be difficult for children to locate the exact area of pain and assessing for abdominal injury can be difficult.
FAST is a rapid ultrasound examination of 4 locations (Figure 1) with the primary objective of detecting free fluid within the abdomen, pleural space, and pericardial sac. In injured adults, FAST is useful in rapidly triaging hemodynamically unstable patients to expedite operative management . Free fluid in any one view deems the FAST positive. However, for a FAST to be determined as negative, each of the landmarks in each individual view must be interrogated and evaluated for the presence of free fluid. The role of FAST in the hemodynamically stable child after blunt abdominal trauma is nuanced.
Figure 1. Location of the 4 FAST views: Right upper quadrant (A), left upper quadrant (B), pelvic (C), subxiphoid (D). Illustration by Dr. Maytal Firnberg.
The FAST can be performed in parallel with the rest of the trauma evaluation. Serial FAST exams can be repeated as needed throughout the child’s ED stay, particularly if the child has an unexplained change in clinical status. For a complete FAST, each of the views needs to be assessed and every landmark in each view must be visualized. In addition to intra-abdominal hemorrhage and pericardial effusion, point-of-care ultrasound can be used to evaluate the thorax for hemothorax and pneumothorax. When included together, this exam is referred to as the extended FAST (E-FAST).
In general, the child should be positioned supine as free fluid will pool in dependent areas (Figure 2). In children, the recto-vesicular or recto-uterine pouch is the most common place for fluid to collect depending on the patient’s sex . Fluid in the abdomen can move freely up the right pericolic gutter into the right upper quadrant. The left pericolic gutter is higher and the phrenicocolic ligament blocks the flow; consequently, fluid tends to flow to the right pericolic area over the left, regardless of injury type.
Some controversy exists about how much free fluid can be detected by the FAST, and most studies focused on adults. For pediatric patients, we are using 100 mL as it was the median quantity of fluid needed for ultrasound detection of the pelvic view .
Figure 2. Free fluid accumulates in dependent areas. In a supine patient, this is the hepato-renal pouch (right upper quadrant view), the spleno-renal pouch (left upper quadrant view), and recto-vesicular or recto-uterine pouch (pelvic view). Illustration by Dr. Maytal Firnberg.
Use a low frequency ultrasound probe: phased array probe (Figure 3) or curvilinear probe (Figure 4).
Phased array probes can generally achieve adequate penetration particularly for smaller pediatric patients and have a smaller footprint allowing for easier intercostal views.
Curvilinear probes allow for further penetration and greater depth of abdominal views and may be useful in larger children.
For the 4 scanning areas, each view must be interrogated completely, and the clinician should identify all key landmarks. The red dot on the probe correlates with the probe marker.
Right Upper Quadrant (RUQ) View
Figure 5. Place the probe in the right mid axillary line (around ribs 8-10) with the probe marker towards the head. Fan anterior and posterior and slide up or down a rib space to view the key landmarks.
Normal View and Landmarks
Figure 6. Normal RUQ ultrasound view with labeled landmarks
Diaphragm (including the subdiaphragmatic intraperitoneal space and supradiaphragmatic intrathoracic space)
Liver (including the caudal tip of the liver)
Kidney (including superior and inferior poles)
Hepatorenal Recess (Morison’s Pouch) – A potential space between the liver and kidney where free fluid can collect
Normal Ultrasound Video
Video 1. Normal RUQ ultrasound view
Left Upper Quadrant (LUQ) View
Figure 7. Place the probe in the left mid or posterior axillary line (around ribs 7-9) with the probe maker towards the head. Fan anterior and posterior and slide up or down a rib space to view the landmarks. In infants and smaller children, the midaxillary line generally provides the best view.
Normal View and Landmarks
Figure 8. Normal LUQ ultrasound view with labeled landmarks
Diaphragm (including the sub- and supradiaphragmatic areas)
Spleen (including splenic tip)
Kidney (including superior and inferior poles)
Splenorenal Recess – a potential space between the spleen and kidney where free fluid can collect
Normal Ultrasound Video
Video 2. Normal LUQ ultrasound view
Figure 9. Place the probe in the midline below the umbilicus and fan or rock the probe down towards the feet until the bladder comes into view. Fan through the entire bladder in both transverse and sagittal orientations. For the transverse and sagittal views, the probe marker should be towards the patient’s right and head, respectively.
Normal View and Landmarks
Figure 10. Normal sagittal (left) and transverse (right) views of the pelvic ultrasound with labeled bladder
Bladder (including anterior and posterior walls)
In patients with uteruses, make sure to visualize the uterus and the recto-uterine space as fluid can collect between the bladder and uterus and also behind the uterus.
Normal Ultrasound Video
Video 3. Normal pelvic ultrasound view (sagittal)
Video 4. Normal pelvic ultrasound view (transverse)
Figure 11. Place the probe under the sternum for a subxiphoid view. Point the probe towards the left shoulder and the probe marker towards the right shoulder. This view requires gentle downward pressure as you drop the angle of the probe down towards the patient. If unable to obtain this subxiphoid view, look parasternally.
Normal View and Landmarks
Figure 12. Normal pericardial subxiphoid ultrasound view with labeled landmarks
Left and right ventricles (atria may also be visible)
Normal Ultrasound Video
Video 5. Normal pericardial ultrasound view (no pericardial effusion and normal contractility)
The aim of the FAST is to identify free fluid in the abdomen, pelvis, pleural, and pericardial spaces.
Free fluid will appear anechoic (black) and will pool in dependent, unobstructed areas. On the right side, fluid in the abdomen can move freely up the pericolic gutter into the right upper quadrant. On the left, the pericolic gutter is higher and the phrenicocolic ligament may impede its flow. The RUQ view is the most sensitive view in adults while the pelvic view is the most sensitive view in children . The following are examples of free fluid identified within the various views of the FAST scan.
Figure 13. RUQ ultrasound view demonstrating free fluid in Morrison’s pouch in an unlabelled (A) and labelled (B) image
Abnormal RUQ Views
Figures 14 (left) and 15 (right). Abnormal RUQ ultrasound views with free fluid. Note that the right image demonstrates free fluid both above and below the diaphragm, meaning fluid that is in the peritoneal and pleural cavities, respectively.
Video 6. Abnormal RUQ ultrasound view with free fluid in the pleural space and Morison’s pouch
Abnormal LUQ Views
Tip: In the LUQ view, the free fluid tends to collect just under the diaphragm. Be sure to look at the diaphragm-spleen interface.
Figure 16. Abnormal LUQ view with free fluid below the diaphragm and above the spleen
Video 7. Abnormal LUQ ultrasound view with free fluid under the diaphragm
Abnormal Pelvic Views
Tip: Free fluid can collect between the bladder and colon in male patients. In female patients, fluid can collect between the bladder and uterus or between the uterus and colon.
Figure 17. Abnormal pelvic view showing free fluid between the bladder and colon
Video 8. Abnormal pelvic ultrasound on sagittal view showing free fluid
These artifacts are cast above the diaphragm in the RUQ and LUQ views.
Figure 19. The RUQ view shows liver parenchyma architecture cephalad of the diaphragm as a mirror artifact.
The spine is not typically seen cephalad to the diaphragm by ultrasound due to air artifact. If the spine is visualized above the diaphragm, this indicates the lungs are no longer filled with air, which normally causes the refraction/reflection of ultrasound waves. This occurs in instances where air is replaced by fluid, such as a pleural effusion or hemothorax, or by a dense consolidation or contusion.
Figure 20. A – The spine is not visualized cephalad to the diaphragm in a normal RUQ ultrasound view. B – A pleural effusion results in a “spine sign” where the spine can be seen extended beyond the diaphragm.
Posterior Acoustic Enhancement
Since the bladder is a fluid filled structure which transmits ultrasound waves well, the waves illuminate the posterior wall of the bladder in a phenomenon called posterior acoustic enhancement. This brightness can hide free fluid settled in the pelvis. Thus, decrease the far field gain (brightness) behind the bladder to avoid missing obscured free fluid.
Figure 21. Bladder view with posterior acoustic enhancement artifact
As blood pools, the ultrasound appearance of clotted blood may have similar echotexture to surrounding soft tissue or organs rather than appear anechoic (black) as typical free fluid.
Figure 22. Bladder view showing hypoechoic clotted blood that may be confused as soft tissue
Due to ultrasound physics and sound wave transmission between structures of different densities, edge artifacts are seen as a dark thin line tracing off the edge of this interface extending to the bottom of the screen. It can be misinterpreted as free fluid.
Figure 23. RUQ view with an edge artifact
A full stomach will appear as a rounded collection of fluid and air anterior to the spleen. It may mimic a free fluid collection. Fan posterior of the stomach to visualize the spleen and perisplenic spaces.
Figure 24. The stomach obscures the LUQ view. Note the mix of bright (air) and dark (other gastric contents) inside the stomach.
Seminal vesicles can appear as hypoechoic, contained, symmetric structures posterior to the bladder in the transverse view and can be mistaken for free fluid.
Figure 25. Bladder view showing hypoechoic seminal vesicles posterior to the bladder
The FAST evaluates for the presence free fluid only .
In trauma, the assumption is that free fluid is due to hemorrhage; however, the FAST cannot adequately distinguish between blood and other types of free fluid, such as ascites or physiologic free fluid.
It does not directly evaluate for injury to solid organs, bowel, diaphragm, or retroperitoneum.
In isolation, the FAST cannot rule out intra-abdominal injury .
The FAST can not detect tiny amounts of hemorrhage.
The scan may appear initially negative with a free fluid volume under a threshold of about 100 mL .
Repeat FAST scans may help detect an accumulation of fluid over time throughout a child’s evaluation.
Trace pelvic free fluid may be physiologic in children, thus limiting specificity .
For adults, the FAST is integral in the diagnostic evaluation after blunt and penetrating trauma . It improves outcomesby decreasing the time to surgical intervention, patient length of stay, surgical complications, CT scan, and diagnostic peritoneal lavage rates .
For children, however, the literature is less clear cut. Pediatric injury patterns commonly result in solid organ lacerations without hemoperitoneum, making the FAST a less sensitive means for detecting important intra-abdominal injury . Further, the test characteristics of the FAST have variable reliability and accuracy in children [7,10,11]. This variation contributes to uncertainty of how to use results of the FAST and decreases its impact on potentially important clinical outcomes such as rates of CT scans and ED length of stay . However…
The FAST is able to identify injuries that the physical exam can miss. When combined with the physical exam, the FAST scan has been found to have better test characteristics than the physical exam alone .
The improvement in POCUS technology, widespread pediatric-specific POCUS expertise, and a focus on clinically relevant outcomes have allowed clinicians to integrate the FAST into novel diagnostic strategies for children after blunt torso trauma .
The pediatric FAST may be used in combination with signs, symptoms, and other diagnostic testing as a screening algorithm to decrease unnecessary CTs. Investigators will need to conduct larger validation trials to confirm and clarify the algorithm.
Studies that have shaped the pediatric FAST literature landscape:
Study Type, Location (Time Frame)
Menaker et al., J Trauma Acute Care Surg 2014 
Secondary Analysis of a Prospective Observational Study
Multicenter (May 2007 to January 2010)
Median age, 11.8 yrs; interquartile range (IQR) 6.3-15.5 yrs
Evaluated the variability of clinician-performed FAST examinations and the use of abdominal CT following FAST examination in children with blunt trauma
373 (5.8%) were diagnosed with intra-abdominal injury
3,015 (46.6%) underwent abdominal CT scanning. Only 887 (13.7%) underwent FAST examination before CT scan.
Use of the FAST increased as clinician suspicion for intra-abdominal injury increased. When clinicians had a lower suspicion, they were significantly less likely to order a CT scan, if a FAST examination was performed.
Holmes et al., JAMA 2017 
Randomized Clinical Trial
University of California, Davis Medical Center (April 2012-May 2015)
Mean 9.7 yrs; SD 5.3 yrs
Studied the impact of the FAST scan on on multiple patient centered outcomes
Hemodynamically stable patients with blunt torso trauma were randomized a FAST or no FAST scan.
50 had intra-abdominal injury, including 40 patients (80%) with intraperitoneal fluid and 9 patients underwent laparotomy.
No difference in the proportion obtaining CT, missed intra-abdominal injuries, length of stay, or cost.
Kornblith et al., Acad Emerg Med 2020 
University of California, Benioff Children’s Hospital Oakland (November 2013 to July 2015)
Median age 8 yr; IQR 4-12 yr
Query of trauma database for children who met institutional trauma activation criteria and who also had a FAST performed.
50 (14%) patients were found to have an intra-abdominal injury with 13 (4%) requiring intervention.
Positive FAST and positive physical exam were found to be independent predictors of intra-abdominal injury, both with a 74% sensitivity.
When combined, FAST and physical exam (FAST-enhanced physical exam) improved sensitivity to 88% (NPV 97.3%).
Liang et al., Pediatr. Emerg Care 2021 
Systematic Review and Meta-Analysis
Multicenter (January 1966- March 2018)
Based on 8 studies, the FAST had a pooled sensitivity of 35% and specificity 96% for intra-abdomianal injury.
All 8 studies were prospective; 1 of the 8 was the 2017 Holmes paper mentioned above .
Conclusion: For a positive FAST, the post-test probability of an intra-abdominal injury was 63% meaning that those patients should get a CT to characterize injury. If the FAST is negative, you may still need a CT, because the post-test probability of intra-abdominal injury was still relatively high at 9%.
None of the studies had low enough negative likelihood ratios to obviate the need for CT.
Although a negative FAST alone does not exclude an intra-abdominal injury, it can identify low-risk patients with a reassuring physical exam and GCS 14-15.
Kornblith et al., JAMA 2022 
Expert, consensus–based Modified Delphi
International multicenter (May 2021 to June 2021)
Generated definitions for complete pediatric FAST and E-FAST studies in the context of blunt trauma
The use of FAST in pediatric trauma is an evolving area of active research. A clear consensus on the way the FAST fits into pediatric trauma protocols is yet to be determined. Studies will need to be performed to examine the benefits of serial FAST, patient factors that may influence its test characteristics, and effect on patient centered outcomes.
There are a number of strategies to incorporate the above studies into clinical care, and one example is illustrated in the algorithm below. Keep in mind that FAST should be used in conjunction with other signs and symptoms of intra-abdominal injury (vomiting, decrease breath sounds, abdominal pain, thoracic wall trauma). Also consider laboratory testing such as liver function tests and urinalysis, depending on the clinical context and consulting your surgical colleagues.
The primary survey is completed with airway, breathing, and circulation noted to be intact. As someone starts the secondary survey, you grab a phased array probe and perform a FAST . You observe the following:
Pelvis View, Sagittal
Pelvis View, Transverse
You call out ‘FAST negative’ to the documenting nurse and team leader.
The patient has radiographs performed of his chest, pelvis, neck, and right forearm. He is diagnosed with a type 3 supracondylar humeral fracture but the other radiographs are negative for fracture and pneumothorax. The rest of his evaluation is reassuring. Orthopedics is consulted and they admit him for surgery. He is discharged home the next day with pediatrician follow up.
Pediatrician Clinic Follow-Up
At her pediatrician clinic visit 1 week later, he is playful and active with his arm in a cast. He has been eating and drinking normally without any complaints of abdominal pain. He has orthopedics follow up scheduled for the following week.
Kenefake ME, Swarm M, Walthall J. Nuances in Pediatric Trauma. Emerg Med Clin North Am. 2013;31(3):627-652. doi:10.1016/j.emc.2013.04.004
Melniker LA, Leibner E, McKenney MG, Lopez P, Briggs WM, Mancuso CA. 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(3):227-235. doi:10.1016/j.annemergmed.2006.01.008
Brenkert TE, Adams C, Vieira RL, Rempell RG. Peritoneal fluid localization on FAST examination in the pediatric trauma patient. Am J Emerg Med. 2017;35(10):1497-1499. doi:10.1016/j.ajem.2017.04.025
Jehle DVK, Stiller G, Wagner D. Sensitivity in Detecting Free Intraperitoneal Fluid With the Pelvic Views of the FAST Exam.
Netherton S, Milenkovic V, Taylor M, Davis PJ. Diagnostic accuracy of eFAST in the trauma patient: a systematic review and meta-analysis. CJEM. 2019;21(6):727-738. doi:10.1017/cem.2019.381
Menaker J, Blumberg S, Wisner DH, et al. Use of the focused assessment with sonography for trauma (FAST) examination and its impact on abdominal computed tomography use in hemodynamically stable children with blunt torso trauma. J Trauma Acute Care Surg. 2014;77(3):427-432. doi:10.1097/TA.0000000000000296
Berona K, Kang T, Rose E. Pelvic Free Fluid in Asymptomatic Pediatric Blunt Abdominal Trauma Patients: A Case Series and Review of the Literature. J Emerg Med. 2016;50(5):753-758. doi:10.1016/j.jemermed.2016.01.003
Holmes JF, Gladman A, Chang CH. Performance of abdominal ultrasonography in pediatric blunt trauma patients: a meta-analysis. J Pediatr Surg. 2007;42(9):1588-1594. doi:10.1016/j.jpedsurg.2007.04.023
Liang T, Roseman E, Gao M, Sinert R. The Utility of the Focused Assessment With Sonography in Trauma Examination in Pediatric Blunt Abdominal Trauma: A Systematic Review and Meta-Analysis. Pediatr Emerg Care. 2021;37(2):108-118. doi:10.1097/PEC.0000000000001755
Holmes JF, Kelley KM, Wootton-Gorges SL, et al. Effect of Abdominal Ultrasound on Clinical Care, Outcomes, and Resource Use Among Children With Blunt Torso Trauma: A Randomized Clinical Trial. JAMA. 2017;317(22):2290-2296. doi:10.1001/jama.2017.6322
Kornblith AE, Graf J, Addo N, et al. The Utility of Focused Assessment With Sonography for Trauma Enhanced Physical Examination in Children With Blunt Torso Trauma. Acad Emerg Med Off J Soc Acad Emerg Med. 2020;27(9):866-875. doi:10.1111/acem.13959
Riera A, Hayward H, Torres Silva C, Chen L. Reevaluation of FAST Sensitivity in Pediatric Blunt Abdominal Trauma Patients: Should We Redefine the Qualitative Threshold for Significant Hemoperitoneum? Pediatr Emerg Care. 2021;37(12):e1012. doi:10.1097/PEC.0000000000001877
Kornblith AE, Addo N, Plasencia M, et al. Development of a Consensus-Based Definition of Focused Assessment With Sonography for Trauma in Children. JAMA Netw Open. 2022;5(3):e222922. Published 2022 Mar 1. doi:10.1001/jamanetworkopen.2022.2922