A 28-year-old woman involved in a rollover accident presents with severe abdominal pain, tachycardia (HR 118/min), and hypotension (BP 88/54 mmHg). On examination, she has bruising over the left flank and left upper quadrant tenderness. Two large-bore IVs are established and fluid resuscitation initiated. What is the most appropriate investigation of choice to detect intra-abdominal bleeding and guide management decisions in this hemodynamically unstable patient?

Explanation

## Abdominal Trauma Assessment in the Unstable Patient **Key Point:** FAST (Focused Assessment with Sonography for Trauma) is the **investigation of choice** for hemodynamically unstable patients with suspected intra-abdominal bleeding in the primary/secondary survey. ### Why FAST Is Optimal **High-Yield:** FAST has become the standard of care in ATLS for rapid detection of free fluid (blood) in trauma patients because it: 1. **Rapid:** Can be completed in 2–3 minutes at the bedside 2. **Non-invasive:** No radiation, no contrast, no transfer required 3. **Sensitive:** Detects as little as 250 mL of free fluid in the pelvis 4. **Portable:** Performed in the resuscitation bay without leaving the patient 5. **Repeatable:** Can be done serially to assess response to resuscitation ### FAST Views (4-Point Exam) | View | Anatomy Assessed | Pathology Detected | |---|---|---| | **Perihepatic (Morrison's pouch)** | Right upper quadrant | Free fluid in hepatorenal recess | | **Perisplenic** | Left upper quadrant | Free fluid around spleen | | **Pelvic** | Suprapubic region | Free fluid in pelvis (most sensitive site) | | **Pericardial** | Subxiphoid | Hemopericardium/tamponade | **Clinical Pearl:** A positive FAST in a hypotensive patient with blunt abdominal trauma is an indication for **emergency laparotomy** (or resuscitative endovascular balloon occlusion of the aorta [REBOA] in select centers). No further imaging is needed. ### Why Other Options Are Suboptimal | Investigation | Limitation | |---|---| | **DPL** | Invasive, requires local anesthesia, takes longer than FAST, now largely replaced by FAST; still useful if FAST is equivocal | | **CT abdomen/pelvis** | Requires patient transfer, time-consuming, contraindicated in unstable patients; reserved for stable patients in secondary survey | | **Serial exam + labs** | Useful adjuncts but NOT diagnostic; cannot replace imaging for detecting free fluid | **Mnemonic: FAST Indications** — **STAB** - S = Shock / Unstable hemodynamics - T = Trauma (blunt or penetrating) - A = Abdominal tenderness / Mechanism - B = Bedside / Rapid assessment needed **Warning:** ~~DPL~~ is now considered obsolete in most trauma centers; FAST has superior sensitivity, specificity, and speed. Do not confuse FAST with DPL in modern ATLS protocols.