Sonographic Assessment of Blunt Abdominal Trauma in the Emergency Department: The FAST Exam Mark Brown, MS-4 OHSU

Blunt Abdominal Trauma (BAT) Most common trauma mechanism in the United States. Possibility for multiple injuries to solid abdominal viscera, hollow organs, retroperitoneum, vascular/nervous structures and musculoskeletal system. Notoriously difficult to diagnose.

Blunt Abdominal Trauma (BAT) Abdominal Injury Diagnostic Modalities Physical Exam Diagnostic Peritoneal Lavage (DPL) Computerized Tomography (CT) Focused Assessment with Sonography for Trauma (FAST)

Blunt Abdominal Trauma (BAT) Physical Exam Easy and Fast but… Unreliable Poor sensitivity and specificity Distracting injuries Many injuries do not present with pain or will not develop pain for several hours Must be repeated often dicine/pulmonar/pd/pstep46.htm

Blunt Abdominal Trauma (BAT) DPL Easy and Fast but… Invasive, 1% complication rate High false positive rate: DPL alone results in unnecessary laparotomies in 30% of cases. Misses retroperitoneal injury

Blunt Abdominal Trauma (BAT) CT Sensitive and Specific Can diagnose organ specific injury and retroperitoneal injury Also will diagnose bone injury but… Radiation Requires a stable patient for transport IV contrast Expensive

Blunt Abdominal Trauma (BAT) FAST Easy and well…Fast but… Variable Sensitivity Operator Dependant Misses retroperitoneal injury

Blunt Abdominal Trauma (BAT) FAST Exam Ultrasound examination of 4 areas to determine whether or not there is fluid present Perihepatic, perisplenic, pelvic and pericardial areas. PerihepaticPericardial PelvicPerisplenic

Blunt Abdominal Trauma (BAT) FAST Exam Example of a positive FAST Exam demonstrating blood surrounding the liver Liver parenchyma Perihepatic fluid collection images/A-031.jpg

Blunt Abdominal Trauma (BAT) Another example…

Blunt Abdominal Trauma (BAT) Normal view of Morrison’s Pouch Positive FAST of Morrison’s Pouch

Blunt Abdominal Trauma (BAT) Normal subcostal view of pericardium Positive FAST demonstrating pericardial effusion

Blunt Abdominal Trauma (BAT) FAST demonstrating blood surrounding the uterus…

Blunt Abdominal Trauma (BAT) FAST demonstrating blood surrounding the spleen…

Blunt Abdominal Trauma (BAT) FAST sensitivity & specificity data Studynsensitivity(%)specificity(%)npv(%) Ballard et al, Boulanger et al, Chiu et al, Coley et al, Hoffmann et al, Ingeman et al, Kern et al, Liu et al, McElveen et al, McKenney et al, Rozycki et al, Rozycki et al, Rozycki et al, Shackford et al, Thomas et al, Tso et al, Wherret et al, Yeo et al, Total

Blunt Abdominal Trauma (BAT) FAST Data Wide fluctuation in sensitivity data for FAST (28%-92%) Explanations? Operator dependant? Steepness of learning curve? Definition of False Negatives? As usual, the answer is in the details

Blunt Abdominal Trauma (BAT) Operator Dependant? Several studies looking at learning curve and competency by non- radiologists. Those that examine only the FAST, (as opposed to ultrasound in general) report high accuracy rates for both radiologists and non- radiologists. In a study with 4,941 pts surgeons were found to have an accuracy rate of 97.5%. In a study of 997 pts with FAST performed by radiologists, the accuracy was 97.8%.

Blunt Abdominal Trauma (BAT) Although ultrasound as a field may be very operator dependant, the focused, binary nature of the FAST (fluid or no fluid) seems to be fairly consistent among providers. Why does sensitivity vary so much and why should the FAST be interpreted as a limited study?

Blunt Abdominal Trauma (BAT) Definitions of False Negatives The drawbacks of the FAST and the variability in sensitivity are most likely the result of its poor performance in detecting retroperitoneal and hollow organ injury. False Negative FAST neg for blood Gold standard found blood OR FAST neg for blood Gold standard found an injury (retroperitoneal, hollow organ, etc.) that does not demonstrate hemoperitoneum as a finding.

Blunt Abdominal Trauma (BAT) False Negatives The FAST may be fairly sensitive for hemoperitoneum but cannot detect other abdominal trauma, limiting its use as a screening tool.

Blunt Abdominal Trauma (BAT) Common FAST Algorithm FAST + Free Fluid - Free Fluid StableUnstable CTLAP Follow-up Repeat FAST Stable Unstable Indeterminate Repeat FAST, DPL, or CT

Blunt Abdominal Trauma (BAT) With this algorithm, the decision comes down to what an acceptable error rate is? One can either accept the error rate of the FAST and choose to repeat if initially negative…or Choose not to include the FAST exam in the algorithm as Stable patients would then get CT or DPL and unstable patients would immediately go to the OR…

Blunt Abdominal Trauma (BAT) However, this would undoubtedly cause an unacceptable amount of CT scans as there is ample evidence that one can not rely on the physical exam in abdominal trauma. If the FAST was to be incorporated as a “pre- screen” type procedure with a low error threshold then the algorithm might look something like this…

Blunt Abdominal Trauma (BAT) Altered “pre-screen” FAST Algorithm FAST + Free Fluid - Free Fluid StableUnstable CTLAP Follow-up LAP Stable Unstable Indeterminate Repeat FAST, DPL, or CT

Blunt Abdominal Trauma (BAT) This would obviously decrease the error rate of the overall trauma algorithm but increase unnecessary laparotomies. Ideally one could employ CT but unstable pts cannot be moved to the scanner; hence the benefit of a portable technology such as ultrasound.

Blunt Abdominal Trauma (BAT) In conclusion, the FAST exam may be able to be performed accurately by non- radiologists in the trauma setting but is hindered by the inability to detect certain traumatic abdominal injuries. However, given its ability to be employed rapidly and non-invasively in the unstable patient, it can be useful as a “pre- screening” tool as long as its limitations are recognized and the possibility of false- negatives are considered.

Bibliography 1.Boulanger, B. ET al. “The Indeterminate Abdominal Sonogram in Multisystem Blunt Trauma.” J Trauma, Vol 45(1) July Dolich, M. ET al. “2,576 Ultrasounds for Blunt Abdominal Trauma.” J Trauma, Vol 50(1) Jan McCarter, F. ET al. “Institutional and Individual Learning Curves for FAST.” Annals of Surgery, Vol 231(5) McKenny, M ET al. “1,000 Consecutive Ultrasounds for Blunt Abdominal Trauma.” J Trauma, Vol 40(4) April Miller, M. ET al. “Not So Fast.” J Trauma, Vol 54(1) Rozycki, G. ET al. “Ultrasound, What Every Trauma Surgeon Should Know.” J Trauma, Vol 40(1) Jan Shackford, S. Et al. “FAST: The Learning Curve of Nonradiologist Clinicians in Detecting Hemoperitoneum.” J Trauma, Vol 46(4) April Thomas, B. ET al. “Ultrasound Evaluation of Blunt Abdominal Trauma: Implementation, Initial Experience, and Learning Curve.” J Trauma, Vol 42(3) March Tintinalli, J. Et al. Emergency Medicine: A Comprehensive Study Guide, 6 th Ed. ACEP,