A 32-year-old male presents to the emergency department 20 minutes after a motor vehicle collision with blunt abdominal trauma. He is haemodynamically stable (BP 128/82, HR 92), alert, and complaining of left-sided abdominal pain. Physical examination reveals tenderness in the left upper quadrant with mild guarding. Which is the investigation of choice to assess for intra-abdominal injury in this haemodynamically stable patient?

Explanation

## Investigation of Choice in Stable Blunt Abdominal Trauma **Key Point:** In a haemodynamically stable patient with blunt abdominal trauma, CT abdomen and pelvis with IV contrast is the investigation of choice because it provides the highest sensitivity and specificity for detecting solid organ injuries, retroperitoneal bleeding, and other intra-abdominal pathology. ### Why CT is Superior in This Scenario **High-Yield:** CT imaging allows: - Detailed assessment of parenchymal injuries (liver, spleen, kidney) - Detection of active bleeding (arterial extravasation) - Identification of hollow viscus injuries - Evaluation of retroperitoneal structures - Grading of solid organ injuries to guide conservative vs. operative management ### Role of FAST in Trauma Algorithm **Clinical Pearl:** FAST is the first-line imaging modality in the **primary survey** of haemodynamically unstable patients or those requiring rapid assessment in the resuscitation bay. It detects free intra-peritoneal fluid (blood) but does NOT identify the source or grade the injury. ### Comparison of Imaging Modalities | Investigation | Sensitivity | Specificity | Time | Use Case | Limitations | |---|---|---|---|---|---| | FAST | 73–96% (free fluid) | 95–100% | <5 min | Unstable patients, rapid screening | Cannot grade organ injury; operator-dependent | | CT (IV contrast) | 95–100% | 95–100% | 10–15 min | Stable patients, detailed assessment | Requires transport; radiation; contrast allergy risk | | DPL | 96–98% | 97–99% | 5–10 min | Historical; rarely used now | Invasive; cannot grade injury; high false-positive rate | | Exploratory laparotomy | N/A | N/A | N/A | Therapeutic, not diagnostic | Invasive; reserved for unstable patients or clear indication | **Mnemonic:** **FAST-CT Algorithm** — FAST in unstable (primary survey), CT in stable (secondary survey). ### Clinical Context This patient is: - Haemodynamically stable (BP normal, HR <100) - Alert and oriented - Localized tenderness without peritonitis These features permit time for detailed imaging. CT will guide whether the patient needs operative intervention or can be managed conservatively with serial examination and imaging. [cite:ATLS 10th Edition, Chapter 5]