The FAST Exam Trap: Lessons from a Trauma Malpractice Case

Joshua Guttman, MD FRCPC, FAAEM, FACEP, FAEMUS

Recently, the Expert Witness Newsletter reviewed a malpractice case involving the use of a FAST exam in a trauma patient. The case offers important lessons about how point-of-care ultrasound (POCUS), particularly the FAST exam, should and should not be used in trauma care.

The Case

A 79-year-old man was involved in a motor vehicle collision and was brought to the emergency department. During his evaluation, the emergency physician performed a FAST exam, which was documented as negative. Based on the clinical assessment and the negative ultrasound, the patient was discharged without undergoing a CT scan to rule out intraabdominal injuries.

Three days later, the patient returned with severe abdominal pain and shortness of breath. A repeat FAST exam demonstrated a large amount of free fluid in the abdomen. The patient was taken emergently to the operating room, where hemoperitoneum from a splenic injury was identified. A splenectomy was performed.

Although the patient ultimately died from causes unrelated to the missed splenic injury, the case progressed to litigation. During deposition, opposing counsel criticized the treating physician’s decision-making. Specifically, they focused on the fact that a FAST exam had been performed but a CT scan had not been ordered.

The argument was that the physician had enough concern for intra-abdominal injury to perform an imaging test but chose one that was not sufficiently sensitive to rule out injury.

Malpractice cases where POCUS represents a main claim are rare.^1-4 This case represents one of the first examples, if not the first example, where the FAST exam itself was raised as a central issue in a malpractice claim.

Understanding the FAST Exam

To understand the legal argument, it’s important to revisit the clinical purpose and limitations of the FAST exam.

The FAST exam was originally developed for hemodynamically unstable trauma patients.⁵ In this context, its role is not to rule out intra-abdominal injury completely but to rapidly detect significant hemoperitoneum that would cause hemodynamic instability. The FAST exam would then justify emergent surgical intervention without waiting for a CT scan.

The exam reliably detects approximately 500 mL or more of intraperitoneal blood. Smaller volumes are often missed. As a result, the sensitivity of FAST for detecting intra-abdominal injury in hemodynamically stable patients is only about 70-80%.

In unstable trauma patients, however, this limitation is far less problematic. If a patient is unstable due to intra-abdominal bleeding, the volume of blood in the peritoneum is typically well above the detection threshold, often exceeding one liter. In those circumstances, FAST can rapidly identify the abdomen/peritoneum as the source of instability and expedite surgical management without delaying care for CT imaging.

In other words, FAST is a decision tool for unstable patients, not a screening test to rule out injury in stable ones.

How FAST Became Overused

As POCUS became more widespread, FAST exams were increasingly incorporated into trauma workflows, especially in academic trauma centers.

These environments are designed for training, and FAST exams are frequently performed on all trauma patients, regardless of stability. The goal is to give residents repeated exposure to the exam so they can develop proficiency for when it is truly needed.

Over time, this practice created a misconception among trainees: that FAST should be performed in every trauma patient. There is sometimes a misguided belief that the American College of Surgeons (ACS) mandates that a FAST must be performed on every trauma patient.

However, the ACS trauma guidelines do not mandate FAST in all trauma patients. Instead, the exam is intended primarily for hemodynamically unstable trauma patients.⁶

When FAST is used outside this context, its limitations become more problematic. A negative FAST in a stable patient can create a false sense of reassurance, even though the test is not sensitive enough to rule out injury.

That appears to be exactly what occurred in this case.

The Legal Problem Created by Performing FAST

In hindsight, the legal vulnerability in this case stems from the decision to perform a test.

If the physician had not performed any imaging, the defense could reasonably argue that the clinical concern for intra-abdominal injury was low. The decision to discharge the patient without imaging could then be framed as a clinical judgment based on history, examination, and overall risk assessment.

Instead, imaging was performed, but it was an imaging modality with poor sensitivity for the condition in question.

From a legal standpoint, this creates a powerful argument:

The physician was concerned enough to order a test but did not order the correct test. While it can be difficult to judge the history and physical exam retrospectively, it is easy to argue the diagnostic accuracy of POCUS vs CT in stable trauma patients.

An analogy might help illustrate the issue. Consider a patient with suspected small bowel obstruction. If a clinician is concerned about obstruction but orders only a plain abdominal X-ray, despite knowing that CT is far more sensitive, and then discharges the patient after a negative X-ray, that decision could easily be criticized during deposition or at trial.

The same reasoning can be applied to the FAST exam in a stable trauma patient.

The Archiving Issue: A Potential Second Liability

There is another potential issue in this case that was not raised by opposing counsel but easily could have been.

If ultrasound images are not archived, there is no objective record of the exam. In that situation, an attorney could argue that the FAST exam may actually have been positive, but the physician misinterpreted the images. It is not known whether in this case the images were archived.

Without stored images, the physician has no way to demonstrate what the exam actually showed.

This is precisely why the ACS trauma guidelines require an image archiving and documentation system for ultrasound examinations. Archiving images not only supports quality assurance programs but also protects clinicians by providing an objective record of the exam.

If a system lacks archiving capability, or if images are simply not saved, the physician may be left without a strong defense against claims of misinterpretation.

Key Lessons from This Case

As POCUS becomes increasingly integrated into clinical practice, cases involving POCUS will likely become more common. Each one offers valuable lessons for clinicians.

Several key takeaways emerge from this case:

1. Understand the performance characteristics of the POCUS exams you perform.
   Knowing the sensitivity, specificity, and clinical indications of each exam is essential for safe and defensible practice.
2. FAST is not sensitive enough to rule out intra-abdominal injury in hemodynamically stable patients.
   In stable trauma patients, imaging decisions should generally be based on clinical risk assessment and CT when indicated. Either a CT is indicated or no imaging is indicated.
3. Be mindful of what your chart communicates.
   If a FAST exam is performed but CT imaging is not obtained, the documentation may imply that the physician was concerned about intra-abdominal injury but chose an inadequate test.
4. If FAST is performed purely for educational purposes, document it clearly.
   Otherwise, the exam may appear to have been part of the diagnostic decision-making.
5. Always archive images and document the study appropriately.
   Image storage provides both quality assurance and medicolegal protection.

Conclusion

Point-of-care ultrasound (POCUS) has transformed bedside diagnosis and clinical decision-making. But as its use expands, so does the importance of using the right test in the right patient for the right reason.

The FAST exam remains a crucial test in the hemodynamically unstable trauma patient, but it is not a screening test capable of ruling out intra-abdominal injury in stable patients.

This case reminds us that POCUS is not immune to the same medicolegal scrutiny applied to any other diagnostic test. Understanding its limitations, documenting its use appropriately, archiving all images, and integrating it thoughtfully into clinical decision-making are essential to ensuring that it improves patient care without creating unintended legal risk.

References

1. Blaivas M, Pawl R. Analysis of lawsuits filed against emergency physicians for point-of-care emergency ultrasound examination performance and interpretation over a 20-year period. Am J Emerg Med. 2012;30(2):338-341. doi:10.1016/j.ajem.2010.12.016
2. Stolz L, O'Brien KM, Miller ML, Winters-Brown ND, Blaivas M, Adhikari S. A review of lawsuits related to point-of-care emergency ultrasound applications. West J Emerg Med. 2015;16(1):1-4. doi:10.5811/westjem.2014.11.23592
3. Russ B, Arthur J, Lewis Z, Snead G. A review of lawsuits related to point-of-care emergency ultrasound applications. J Emerg Med. 2022;63(5):661-672. doi:10.1016/j.jemermed.2022.04.020
4. Prager R, Wu D, Garber G, et al. Medico-legal risks of point-of-care ultrasound: a closed-case analysis of Canadian Medical Protective Association medico-legal cases. Ultrasound J. 2024;16(1):16. Published 2024 Feb 23. doi:10.1186/s13089-024-00364-7
5. Kimura A, Otsuka T. Emergency center ultrasonography in the evaluation of hemoperitoneum: a prospective study. J Trauma. 1991;31(1):20-23. doi:10.1097/00005373-199101000-00004
6. Bloom BA, Gibbons RC. Focused assessment with sonography for trauma. [Updated 2023 Jul 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing.