The FAST exam in trauma is primarily used to detect which finding?

• A. Intra-abdominal gas
• B. Free intraperitoneal fluid suggesting intra-abdominal injury
• C. Pericardial effusion
• D. Retroperitoneal hematoma

Answer: (B)

In trauma care, the FAST exam is a bedside ultrasound aimed at rapidly identifying free fluid in the abdominal and pericardial spaces. Its main purpose is to detect free intraperitoneal fluid that suggests intra-abdominal injury or active hemorrhage, which helps decide if urgent surgical intervention or rapid resuscitation is needed. The exam views potential spaces where fluid collects, such as the hepatorenal recess (Morison’s pouch), the splenorenal recess, the pelvis, and a cardiac window for possible tamponade. Gas patterns or bowel findings aren’t the primary target, and while pericardial fluid can be seen, the crucial takeaway is free intraperitoneal fluid. FAST is less reliable for retroperitoneal injuries, which may require CT for evaluation.