This patient has sustained blunt abdominal trauma from his seat belt. This is indicated by the linear area of ecchymoses, known as a “seat belt sign”. This is a worrisome physical exam finding that should raise a concern about a severe intra-abdominal injury. All trauma patients presenting to the emergency department should be assessed using an organized approach, including a primary survey (“ABCs”) followed by a secondary survey (more detailed physical examination). The FAST (Focused Assessment with Sonography in Trauma) examination is part of the primary survey in a trauma patient. Some sources abbreviate the primary survey in trauma as “ABCDEF”, which stands for Airway, Breathing, Circulation, Disability, Exposure, FAST exam. The primary survey attempts to identify any life-threatening diagnoses that need to be addressed in a time-sensitive manner. Examples include cardiac tamponade, tension pneumothorax, and intra-abdominal bleeding. The FAST exam includes 4 basic views: the right upper quadrant view (liver and right kidney), pelvis view (bladder), left upper quadrant view (spleen and left kidney), and cardiac/subxiphoid view (heart). An E-FAST, or extended FAST, includes the four standard FAST views plus bilateral views of the lungs to evaluate for pneumothorax. An abnormal FAST exam demonstrates the presence of free fluid on ultrasound. In the setting of trauma, free fluid is assumed to be blood. Free fluid on ultrasound appears black, or anechoic (indicated by yellow arrows in below image).

The space between the liver and right kidney (“Morrison’s Pouch”) is often the first location or blood to accumulate in a patient with intra-abdominal bleeding. Trauma patients who are hemodynamically unstable with a positive FAST exam (this patient) should go to the operating room for emergent exploratory laparotomy (Choice C) to determine the source of their bleeding. Performing a CT scan of the abdomen and pelvis (Choice A) would be the correct answer if the patient was hemodynamically stable and had a positive FAST exam. Allowing this patient to leave the emergency department for a CT scan would be dangerous as this patient could rapidly decompensate. Performing a Diagnostic Peritoneal Lavage (Choice B) would be the correct answer if the patient was hemodynamically stable but had a normal FAST exam. An emergent thoracotomy (Choice D) is more typically performed in patients with penetrating trauma who have cardiac arrest shortly before presenting to the emergency department. This intervention attempts to identify and treat any reversible causes of cardiac arrest. Correct Answer: C