# Polytrauma CT: Systematic Interpretation of the Trauma Pan-Scan

## Introduction

The **whole-body CT (WBCT)** or "trauma pan-scan" has become the standard of care in the initial imaging evaluation of polytrauma patients. Covering the head, cervical spine, chest, abdomen, and pelvis with intravenous contrast, it allows rapid detection of life-threatening injuries. The radiologist must provide a rapid, systematic, and complete interpretation -- missed injuries in the trauma setting carry significant medicolegal and clinical consequences.

## Indications for Trauma Pan-Scan

Indications include **high-energy mechanism** (motor vehicle collision, fall from height, pedestrian struck, blast injury), **Glasgow Coma Scale (GCS) of 13 or less** or altered mental status, **hemodynamic instability** or clinical signs of hemorrhage, **multiple suspected injury regions**, and institutional trauma activation criteria.

## Protocol Considerations

**Non-contrast head CT** is obtained for intracranial hemorrhage because contrast may obscure acute blood. **Cervical spine CT** includes bone algorithm reconstructions in sagittal and coronal planes. **Chest, abdomen, and pelvis (CAP)** are imaged in the arterial and/or **portal venous phase** with IV contrast; the arterial phase optimizes detection of active hemorrhage and vascular injury, while the portal venous phase (60-70 seconds) is best for solid organ injury characterization. **Delayed images** (5-10 minutes) are obtained for suspected urothelial or renal collecting system injury. **CT angiography of the neck** is added when cervical vascular injury is suspected, such as with a seatbelt sign or C-spine fracture through the foramen transversarium.

## Systematic Interpretation: A Search Pattern

A disciplined approach prevents missed injuries. One effective framework is the **"outside-in"** method.

### Step 1: Soft Tissues and Body Wall

Evaluate for subcutaneous emphysema (pneumothorax, laryngotracheal injury), body wall hematoma (abdominal wall, retroperitoneal), and the seatbelt sign (subcutaneous fat stranding along the lap belt distribution).

### Step 2: Bones and Spine

Examine cervical, thoracic, and lumbar spine fractures on every vertebral body using sagittal reformats. Count and locate rib fractures (flail chest equals 3 or more consecutive ribs fractured in two places). Identify sternal fractures (associated with cardiac and aortic injury), pelvic ring disruption (classify using Young-Burgess or Tile), and long bone fractures visible at scan margins.

### Step 3: Pleural Spaces

**Pneumothorax** appears as anterior air collection in the supine patient; occult pneumothorax may be seen only on CT. **Hemothorax** presents as high-density layering pleural fluid. **Tension physiology** shows mediastinal shift and a flattened IVC.

### Step 4: Mediastinum and Great Vessels

**Aortic injury** manifests as intimal flap, pseudoaneurysm, periaortic hematoma, or active extravasation at the aortic isthmus. **Mediastinal hematoma** produces a widened mediastinum and obscured aortic contour. Cardiac injury includes hemopericardium and cardiac chamber rupture (rare on CT).

### Step 5: Lungs and Airways

Pulmonary contusion appears as ground-glass opacity or consolidation in a non-anatomic distribution. Pulmonary laceration presents as an air-filled cavity within contused lung. Tracheobronchial injury produces pneumomediastinum, deep cervical emphysema, and the fallen lung sign.

### Step 6: Abdomen -- Solid Organs

**Liver, spleen, and kidneys** are evaluated for lacerations, hematomas, active hemorrhage, and devascularization, graded using the AAST classification. **Pancreatic** injuries include laceration and transection, with evaluation for duct involvement. **Adrenal hemorrhage** may be unilateral or bilateral and may indicate severe deceleration.

### Step 7: Abdomen -- Hollow Viscus and Mesentery

**Bowel injury** manifests as wall thickening, discontinuity, free oral contrast extravasation, mesenteric fat stranding, and unexplained free fluid. **Mesenteric injury** shows active hemorrhage from mesenteric vessels, mesenteric hematoma, and vascular beading or termination. **Free fluid without solid organ injury** is highly suspicious for bowel or mesenteric injury.

### Step 8: Pelvis

**Bladder rupture** is classified as intraperitoneal (contrast extravasation around bowel loops) or extraperitoneal (flame-shaped contrast in perivesical fat). **Urethral injury** should be suspected in males with pelvic fracture and blood at the meatus. **Vascular pelvic hemorrhage** presents as active contrast extravasation adjacent to fracture sites.

![Annotated CT images from a trauma pan-scan demonstrating splenic laceration with active hemorrhage, left hemothorax, and left rib fractures](trauma-pan-scan-annotated.png)

## Active Hemorrhage on CT

**Active arterial extravasation** appears as a focus of hyperattenuating contrast (often greater than 90 HU) within a hematoma or organ parenchyma that does not conform to a vessel. It increases in size and density on delayed images. It is distinguished from a **pseudoaneurysm** (contained, round, matches aortic density) and a **vascular blush** (non-expanding).

## Secondary Survey and Missed Injuries

After the initial rapid interpretation, a systematic **secondary review** should be performed within 12-24 hours. Commonly missed injuries on trauma CT include small pneumothorax (anterior, in the supine patient), non-displaced fractures (spine, pelvis), hollow viscus injury (subtle signs), diaphragmatic rupture (especially left-sided), pancreatic duct injury, and peripheral vascular injury at scan margins.

![CT demonstrating diaphragmatic rupture with herniation of stomach and splenic flexure of colon into the left hemithorax following blunt trauma](diaphragmatic-rupture-ct.png)

![Axial CT showing mesenteric stranding and free fluid between bowel loops without solid organ injury, consistent with mesenteric and possible bowel injury](mesenteric-injury-ct.png)

## Key Clinical Pearls

**Free fluid without solid organ injury** in a trauma patient should be considered mesenteric or bowel injury until proven otherwise. The **aortic isthmus** (just distal to the left subclavian artery origin) is the most common site of traumatic aortic injury. **Delayed images** are essential when collecting system injury is suspected (such as renal laceration extending to the hilum or perinephric fluid). Always scroll to the **margins of the scan** because injuries to the shoulders, proximal femora, and craniovertebral junction are frequently missed. Communicate **critical findings** (active hemorrhage, aortic injury, tension pneumothorax, bowel perforation) immediately to the trauma team -- do not wait for the final report.

## References

1. Huber-Wagner S, Lefering R, Qvick LM, et al. Effect of Whole-Body CT During Trauma Resuscitation on Survival: A Retrospective, Multicentre Study. *Lancet*. 2009;373(9673):1455-1461.
2. Soto JA, Anderson SW. Multidetector CT of Blunt Abdominal Trauma. *Radiology*. 2012;265(3):678-693.
3. Steenburg SD, Ravenel JG, Ikonomidis JS, et al. Acute Traumatic Aortic Injury: Imaging Evaluation and Management. *Radiology*. 2008;248(3):748-762.
4. West OC, Anderson JC. Missed Injuries in Patients with Polytrauma. *AJR Am J Roentgenol*. 2005;184(5):1519-1521.