What are the indications for computed tomography (CT) angiography of the lower extremities in a hemodynamically stable patient with a gunshot wound to the leg?

CT Angiography Indications for Gunshot Wounds of Lower Extremities

In hemodynamically stable patients with lower extremity gunshot wounds, CT angiography should be performed when there are hard signs of vascular injury (active pulsatile bleeding, rapidly expanding hematoma, absent pulse, palpable thrill, or audible bruit), soft signs of vascular injury (history of arterial bleeding, excessive non-pulsatile bleeding, large non-expanding hematoma, major neurological deficit, diminished pulse), proximity to major vessels, or an ankle-brachial index (ABI) <0.9. 1, 2, 3

Hard Signs of Vascular Injury (Strong Indications for CTA)

Immediate CTA is indicated when any of the following hard signs are present in a hemodynamically stable patient: 3, 2

• Active pulsatile bleeding from the wound site
• Rapidly expanding hematoma (this finding has significant positive correlation with arterial injury, p=0.009) 3
• Absent distal pulse (significant positive correlation with arterial injury, p<0.001) 3
• Palpable thrill over the wound
• Audible bruit at the injury site

Approximately 34% of patients with hard signs will have clinically significant arterial injuries on CTA. 3

Soft Signs of Vascular Injury (Moderate Indications for CTA)

CTA should be strongly considered when soft signs are present: 3, 2

• History of arterial bleeding at the scene or during transport
• Excessive non-pulsatile bleeding from the wound
• Large non-expanding hematoma at the injury site
• Major neurological deficit (isolated sensory or motor deficit in the distribution of the injured extremity)
• Diminished but appreciable pulse (significant positive correlation with arterial injury, p<0.001) 3
• Injury site in proximity to main vascular axis (superficial femoral, popliteal, or tibial arteries)

Approximately 11% of patients with soft signs will have clinically significant arterial injuries. 3

Ankle-Brachial Index (ABI) as a Screening Tool

The ABI is a critical decision point in the evaluation algorithm: 4, 5, 2

• ABI <0.9 mandates CTA regardless of other clinical findings, as this threshold has 87% sensitivity and 97% specificity for vascular injury 2
• ABI ≥0.9 with no hard or soft signs allows safe discharge without imaging in isolated lower extremity gunshot wounds without fracture 5
• The mean ABI in patients with vascular injuries is approximately 0.72 4

Diagnostic Performance of CTA

CTA demonstrates excellent diagnostic accuracy for lower extremity vascular injuries: 4, 3, 6

• Sensitivity: 96.2-100% for detecting clinically significant arterial injuries 2, 4
• Specificity: 99.2-100% for vascular injury detection 2, 4
• Image quality is diagnostically excellent in most cases, allowing reliable assessment 6
• CTA detects arterial injury in approximately 30% of patients with lower extremity gunshot wounds who undergo imaging 6

Common Arterial Injuries Detected

The most frequently identified injuries on CTA include: 6, 7

• Focal narrowing/arterial spasm (37% of injuries detected)
• Superficial femoral artery injuries (50% of all arterial injuries)
• Pseudoaneurysm formation
• Active contrast extravasation (indicating active hemorrhage)
• Complete arterial transection or occlusion

Critical Pitfalls to Avoid

Do not rely solely on proximity to major vessels as an indication for CTA, as this has a significant negative correlation with actual arterial injury (p=0.005) and leads to overutilization of imaging. 3

Do not skip CTA when an ABI cannot be reliably obtained due to associated orthopedic injuries (present in 50% of cases), as alternative clinical signs must guide the decision. 4

Do not delay operative exploration for imaging in hemodynamically unstable patients or those with obvious limb-threatening ischemia requiring immediate surgical intervention. 1

Recognize that approximately 5% of patients with no clinical indication for imaging may still have arterial injuries, but routine screening CTA in all gunshot wounds is not cost-effective. 3

Practical Algorithm for Decision-Making

Step 1: Assess hemodynamic stability—if unstable, proceed directly to operative exploration without imaging 1

Step 2: Measure ABI in the injured extremity—if <0.9, obtain CTA 4, 5, 2

Step 3: Evaluate for hard signs (active bleeding, expanding hematoma, absent pulse, thrill, bruit)—if present, obtain CTA 3

Step 4: Evaluate for soft signs (history of bleeding, large hematoma, neurological deficit, diminished pulse)—if present, obtain CTA 3

Step 5: If ABI ≥0.9 and no hard or soft signs are present, the patient can be safely discharged without CTA in isolated lower extremity gunshot wounds without fracture 5

Cost-Effectiveness Considerations

CTA is significantly more cost-effective than conventional angiography, saving approximately $12,922 in patient charges and $1,166 in hospital costs per extremity, while being more rapidly obtained (conventional angiography requires 131±61 minutes to complete versus immediate CTA availability). 4 The algorithm using selective CTA based on ABI and clinical signs costs approximately $992 per patient compared to routine imaging of all patients. 5