1. Correct Answer: B. Repeat eFAST examination

Rationale: Although the first FAST scan was negative, the sensitivity for free fluid detection increases with serial examinations, especially when there are signs of potential ongoing bleeding. In one study, the sensitivity increased from 69% to 85%. This patient would go to the operating room if the eFAST examination was positive, but if the repeat examination does not show hemoperitoneum, other sources of hypotension must be pursued (e.g., retroperitoneal bleeding, cardiogenic shock). If he was stabilized, a CT scan could be performed to evaluate for surgical pathology, but with worsening hypotension it would not be a safe option at this point. Pain may be a cause for tachycardia, but would not address the hypotension.

1. Nunes LW, Simmons S, Hallowell MJ, Kinback R, Trooskin S, Kozar R. Diagnostic performance of trauma US in identifying abdominal or pelvic free fluid and serious abdominal or pelvic injury. Acad Radiol. 2001; 8:128-36.

2. Correct Answer: C. eFAST is highly specific but not sensitive for splenic injury

Rationale: The sensitivity of eFAST to evaluate for retroperitoneal hemorrhage is quite low, with a high false-negative rate. The sensitivity of eFAST to detect abdominal free fluid from splenic injury is around 70%, with a specificity >95%. In the setting of penetrating trauma, sonographic evaluation for pneumothorax, pericardial effusion, hemothorax, and hemoperitoneum, eFAST has excellent specificity. However, ultrasound evaluation for retroperitoneal injury, isolated bowel, or peritoneal injury is limited by very low sensitivity.

1. Netherton S, Milenkovic V, Taylor M, Davis P. Diagnostic accuracy of eFAST in the trauma patient: a systematic review and meta-analysis. CJEM. 2019:1-12.

3. Correct Answer: B. Prostate

Rationale: All of these structures can be seen posterior to the bladder. The prostate is a rounded single structure that can often be seen impinging upon the bladder. Seminal vesicles are anechoic, symmetric, tubular structures that can be confused for free fluid. In contrast to free fluid, they do not layer and track along adjacent structures. Bowel can take various forms on ultrasound, depending on the pathology, but the rectum would be posterior to the prostate in Figure 46.1. In addition, posterior acoustic enhancement may cause increased signal behind an anechoic structure like the bladder, which may obscure small volumes of peritoneal fluid. For all of these reasons, imaging in more than one plane is recommended.

1. Boyd JS, Rupp JD, Ferre RM. Emergency ultrasound. In: Knoop KJ, Stack LB, Storrow AB, Thurman R, eds. The Atlas of Emergency Medicine, 4th ed. McGraw-Hill; Accessed October 11, 2019. http://accessemergencymedicine.mhmedical.com.proxy.library.emory.edu/content.aspx?bookid=1763&sectionid=125439068.

2. Cosby KS, Kendall JL. Practical Guide to Emergency Ultrasound, 2nd ed. Lippincott Williams & Wilkins; 2013.

3. Fritz DA. Emergency bedside ultrasound. In: Stone C, Humphries RL, eds. Current Diagnosis & Treatment: Emergency Medicine, 8th ed. McGraw-Hill; Accessed October 11, 2019. http://accessemergencymedicine.mhmedical.com.proxy.library.emory.edu/content.aspx?bookid=2172&sectionid=165057390.

4. Correct Answer: A. Obtain the images while the bladder is full

Rationale: Evaluation of free fluid in the suprapubic view can be improved if images are obtained while the bladder is full and before a Foley is placed, because this improves the acoustic window. Trendelenburg positioning could improve the detection of fluid in the RUQ or LUQ views, as free fluid would pool in the upper quadrants. Conversely, reverse Trendelenburg positioning may improve the sensitivity of detecting fluid in the pelvis. Scanning in multiple orientations increases the likelihood of detecting an abnormality and distinguishing artifacts.

1. Beard RE, Odom SR. Focused assessment with sonography in Trauma (FAST). In: Brown SM, et al, eds. Comprehensive Critical Care Ultrasound. Society of Critical Care Medicine; 2015:139-149.

2. Richards JR, McGahan JP. Focused Assessment with Sonography in Trauma (FAST) in 2017: what radiologists can learn. Radiology. 2017;283(1):30-48. https://doi.org/10.1148/radiol.2017160107.

5. Correct Answer: A. Right upper quadrant (RUQ)—hepatorenal

Rationale: In a supine patient, the hepatorenal space (Morison’s pouch) is the most dependent portion of the upper abdomen. A complete sonographic view of this space should include the diaphragm and adjacent pleural space, the caudal tip of the liver, and the inferior pole of the kidney. The sensitivity for detection of peritoneal free fluid depends on the mechanism of trauma and pretest probability, but ranges between 70% and 95%. If there are no contraindications, sensitivity can further be optimized by placing the patient in a Trendelenburg position.

1. Gleeson T, Blehar D. Point-of-care ultrasound in trauma. Semin Ultrasound CT MR. 2018;39(4):374-383.

2. Lobo V, Hunter-Behrend M, Cullnan E, et al. Caudal edge of the liver in the right upper quadrant (RUQ) view is the most sensitive area for free fluid on the FAST exam. West J Emerg Med. 2017;18(2):270-280.

6. Correct Answer: A. CT of the abdomen and pelvis with IV contrast

Rationale: This patient has experienced blunt traumatic injury and has objective findings of a “positive seat-belt sign” as well as tachycardia. The clinician should not be falsely reassured by a negative abdominal FAST examination when there is a high pretest probability of significant intra-abdominal injury. Sensitivity for the detection of peritoneal free fluid in a normotensive patient can be as low as 70%, while the sensitivity of CT scan for intra-abdominal injury is ˜97%.

1. Savatmongkorngul S, Wongwaisayawan S, Kaewlai R. Focused assessment with sonography for trauma: current perspectives. Open Access Emerg Med. 2017;9:57-62.

7. Correct Answer: B. Initiate a blood transfusion and take the patient for exploratory laparotomy

Rationale: In an unstable trauma patient with a positive eFAST, the next step in management should be to transfer the patient to the operating room for exploratory laparotomy. It would be reasonable to begin transfusion of blood products in this unstable patient; however, waiting for reassessment of clinical response would be inappropriate and may delay definitive treatment. Similarly, CT scan would delay the necessary intervention to identify and repair a hemodynamically significant source of intra-abdominal bleeding. DPL is used sparingly for equivocal eFAST examination findings, or if it is unclear whether the observed fluid is blood (e.g., ascites).

1. Bowra J. Positive FAST—RUQ—Morrison’s Pouch. The POCUS Atlas. Accessed December 3, 2020. https://www.thepocusatlas.com/trauma/g6302hr5hk6l2cu7vgvwu4yf57y9jn.

2. Britt LD, Andrew B. Peitzman. Acute Care Surgery. Wolters Kluwer Health/Lippincott Williams & Wilkins; 2012. Print.

3. Richards J, McGahan J. Focused Assessment with Sonography in Trauma (FAST) in 2017: what radiologists can learn. Radiology. 2017;283(1):30-48.

8. Correct Answer: B. Placement of right-sided thoracostomy tube

Rationale: Penetrating injuries to the thoracoabdominal region require evaluation for injuries to both intrathoracic as well as intra-abdominal structures. Hemothorax may be identified when examining the upper quadrants of the abdomen during an eFAST examination. CT scan of the chest may be appropriate, but the hemothorax should be addressed immediately since the patient has a clinically significant injury. There is no indication for emergent laparotomy in this hemodynamically stable patient until further workup is completed. There is no apparent indication for immediate endotracheal intubation.

1. Mowery N, Gunter O, Collier B, et al. Practice management guidelines for management of hemothorax and occult pneumothorax. J Trauma Inj Infect Crit Care. 2011;70(2):510-518.

2. Pariyadath M, Snead G. Emergency ultrasound in adults with abdominal and thoracic trauma. In: Post, TW, ed. UpToDate, Waltham, MA; 2019.

9. Correct Answer: D. Discharge home with close outpatient follow-up

Rationale: Though the published specificity for eFAST approaches 100%, several conditions can lead to false positives. Ascites, ventriculoperitoneal shunt overflow, peritoneal dialysate, massive volume resuscitation, or ovarian cyst rupture may all lead to “positive” eFAST examinations. For this patient on peritoneal dialysis, a sonographic evaluation of the abdomen to rule out hemoperitoneum is an inappropriate test. If the clinician has a high suspicion for intra-abdominal injury, a CT scan of the abdomen and pelvis with IV contrast should be performed. In this scenario, the patient is presenting after a low-mechanism motor vehicle collision, has normal vital signs, and a reassuring physical examination, so no further testing is necessary.

1. Pariyadath M, Snead G. Emergency ultrasound in adults with abdominal and thoracic trauma. In: UpToDate, Post, TW, ed. UpToDate, Waltham, MA; 2019.

2. Richards J, McGahan J. Focused Assessment with Sonography in Trauma (FAST) in 2017: what radiologists can learn. Radiology. 2017;283(1):pp. 30-48.

10. Correct Answer: D. Imaging can be improved by having the patient take a deep breath

Rationale: Since the spleen is generally smaller than the liver, the dependent recess of the LUQ is typically more posterior and cephalad compared to the RUQ, consistent with the relative position of the left kidney compared to the right. The probe marker should be directed toward the head with the transducer along the posterior axillary line, while visualizing the subphrenic, splenorenal, and perisplenic spaces. Rotation of the imaging plane (clockwise, usually about 15°) to be parallel with the rib spaces may help minimize shadowing. If the patient is able to participate, holding a breath at deep inhalation may help minimize interference from rib shadowing.

1. Bloom B, Gibbons R. Focused Assessment with Sonography for Trauma (FAST). StatPearls [Internet]. 2019;PMID 29261902.

11. Correct Answer: C. Physiologic fluid since she is a woman of childbearing age

Rationale: A small amount of free fluid (up to 50 mL) in the pelvic view can be a normal finding in women of childbearing age. In trauma patients, fluid more than 50 mL should be considered pathologic and would require additional workup. There is no visible physiologic free fluid in men. In an asymptomatic patient with normal vital signs, additional evaluation is not warranted. Ascites not previously diagnosed is an unlikely cause for this finding. The location of fluid is gravity-dependent, thus in an upright or recumbent patient, even a small volume of peritoneal fluid or blood may collect in the pelvis.

1. Richards J, McGahan J. Focused Assessment with Sonography in Trauma (FAST) in 2017: what radiologists can learn. Radiology. 2017;283(1):30-48.

12. Correct Answer: A. Posterior acoustic enhancement

Rationale: Posterior acoustic enhancement causes areas deep to fluid-filled structures (such as the bladder) to appear brighter and may make it hard to visualize a small volume of free fluid as a result. Reverberation artifact is a result of the ultrasound beam going back and forth between two strong reflectors (e.g., the ultrasound probe and pleura). Reverberation artifact between thickened pleural layers causes comet tail artifacts seen on lung ultrasound in the setting of pulmonary edema. A mirror image artifact results in duplication of objects from strong reflectors (e.g., the appearance of liver in the thorax from a strong reflection from the diaphragm).