# Non-Accidental Trauma: Imaging Findings and Reporting Obligations

## Introduction

Non-accidental trauma (NAT), also termed child abuse, is a critical diagnosis that radiologists must recognize. Imaging findings are often the first evidence of abuse, and the radiologist has a **legal and ethical obligation** to report suspected cases. A thorough understanding of highly specific fracture patterns, intracranial injury, and visceral trauma is essential.

## Epidemiology and Clinical Context

NAT is most common in children **under 2 years of age**. Risk factors include prematurity, disability, young or single parents, substance abuse, and socioeconomic stress. The history provided is often **inconsistent with the severity or pattern of injury**, and multiple injuries at **different stages of healing** are a hallmark finding. Delay in seeking medical care is a concerning feature.

## Skeletal Survey

### Protocol

The **skeletal survey** is the standard imaging evaluation for suspected NAT in children under 2 years. A complete series includes **at least 20 views** covering the entire skeleton: AP views of all extremities (humeri, forearms, femurs, tibiae and fibulae), hands, and feet, plus AP and lateral views of the axial skeleton (skull, spine, chest, pelvis). A **follow-up skeletal survey** at 2 weeks increases detection of occult fractures by 10-25%. A **babygram** (single whole-body image) is inadequate and should never replace a complete skeletal survey.

### Highly Specific Fractures for NAT

| Specificity for NAT | Fracture Type | Mechanism |
|--------------------|---------------|-----------|
| Highly specific | Classic metaphyseal lesions (CMLs/corner/bucket-handle) | Shearing forces at metaphysis |
| Highly specific | Posterior rib fractures | Squeezing chest during shaking |
| Highly specific | Scapular fractures | Significant direct force |
| Highly specific | Spinous process fractures | Direct blow or forced hyperflexion |
| Highly specific | Sternal fractures | Direct blow |
| Moderately specific | Multiple fractures at different healing stages | Repeated trauma |
| Moderately specific | Bilateral fractures in non-ambulatory child | Repeated or excessive force |
| Moderately specific | Complex skull fractures (bilateral, crossing sutures) | High-energy impact |

**Classic metaphyseal lesions (CMLs)**, also called corner fractures or bucket-handle fractures, occur at the metaphysis due to shearing forces and are highly specific for abuse. **Posterior rib fractures** result from squeezing the chest during shaking and are also highly specific. **Scapular fractures** are rare in accidental trauma and require significant force. **Spinous process fractures** indicate direct blows or forceful hyperflexion, and **sternal fractures** are uncommon in accidental pediatric trauma.

### Moderately Specific Fractures

Moderately specific findings include multiple fractures at **different stages of healing**, **bilateral fractures** in a non-ambulatory child, complex skull fractures (bilateral, crossing sutures, diastatic), vertebral body fractures or subluxations, and epiphyseal separations and digital fractures in infants.

## Intracranial Injury

### Abusive Head Trauma (Shaken Baby Syndrome)

**Subdural hematomas (SDH)** are the most common intracranial finding in NAT. SDH of varying ages (mixed density on CT) suggests repeated episodes of trauma. **Interhemispheric SDH** along the falx is highly suspicious for NAT. **Subarachnoid hemorrhage** may accompany subdural collections, and **retinal hemorrhages** are present in 85% of cases and are best documented by ophthalmology.

### Parenchymal Injury

**Diffuse axonal injury (DAI)** results from shearing forces during rotational acceleration-deceleration. **Hypoxic-ischemic injury** may occur due to apnea during shaking episodes. CT shows diffuse cerebral edema with loss of gray-white differentiation. MRI with **diffusion-weighted imaging (DWI)** is more sensitive for early ischemic changes and DAI, and **SWI (susceptibility-weighted imaging)** detects microhemorrhages not visible on CT.

## Visceral Injury

Abdominal injuries in NAT carry the **highest mortality rate**. Characteristic findings include **duodenal hematoma** or perforation from a direct blow to the abdomen, **pancreatic injury** including transection or pseudocyst formation, hepatic and splenic lacerations or subcapsular hematomas, and **hollow viscus perforation** with free intraperitoneal fluid or pneumoperitoneum. CT with IV contrast is the modality of choice for evaluating visceral injuries.

## Differential Diagnosis and Mimics

Several conditions can mimic NAT findings and must be considered. **Osteogenesis imperfecta** presents with multiple fractures along with osteopenia, blue sclerae, and wormian bones. **Rickets** causes metaphyseal fraying and cupping that should not be confused with CMLs. **Menkes disease**, a copper metabolism disorder, causes metaphyseal spurs and subdural hematomas. **Birth trauma** can cause clavicle and humeral fractures that heal within 2-3 weeks. **Normal variants** such as physiologic periosteal reaction in infants (symmetric, smooth, along the diaphysis) should also be recognized.

## Reporting Obligations

### Legal Requirements

**All 50 US states** mandate reporting of suspected child abuse by healthcare providers. Radiologists are **mandatory reporters**, and suspicion alone is sufficient grounds for reporting. Reports should be made to **Child Protective Services (CPS)** and/or law enforcement. **Failure to report** carries legal penalties including fines and potential criminal charges, while good faith reporters are **protected from liability** by law.

### Documentation Best Practices

Radiologists should use objective, descriptive language in the radiology report and clearly state that findings are **"concerning for" or "suspicious for non-accidental trauma."** Definitive statements about the perpetrator or intent should be avoided. Documentation should include communication with the referring clinician and the time of notification. A follow-up skeletal survey at 2 weeks and an ophthalmologic examination should be recommended.

## Clinical Pearls

**Classic metaphyseal lesions and posterior rib fractures** are the most specific skeletal findings for NAT. Multiple fractures at different stages of healing in a child under 2 should raise immediate concern. A **follow-up skeletal survey at 2 weeks** detects additional fractures in up to 25% of cases. Radiologists are mandatory reporters, and a good faith report based on imaging suspicion is both legally required and legally protected.

## References

1. ACR Appropriateness Criteria: Suspected Physical Abuse in Children. *J Am Coll Radiol*. 2017;14(5S):S338-S349.
2. Classic Metaphyseal Lesion in Infants: A Systematic Review. *Pediatr Radiol*. 2018;48(11):1543-1555.
3. Abusive Head Trauma in Infants and Children. *Radiographics*. 2019;39(4):1064-1084.
4. The Role of Imaging in Child Abuse. *Radiology*. 2020;295(3):517-530.