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CHEST TRAUMA IN CHILDREN:CURRENT IMAGING GUIDELINES

AND TECHNIQUES

.Trauma to the pediatric chest,

1-isolation2-polytrauma ,

1-minor 2-life-threatenin .

The challengein pediatric trauma imaging is to implement a problem-oriented approach that

addresses the specific mechanism of injury and clinical presentation.

• diagnostically accurate,

• cost-effective,

•

•efficient treatment decisions,

• using the lowest possible radiation dose.

• The currently availableimaging modalities for evaluating chest trauma

•include chest radiography, ultrasound, and CT•scan.

•Chest radiography

• relatively low radiation-dose study

• ultrasound does not use ionizing radiation

•but they both have limitations in•the setting of chest trauma in children

•MultidetectorCT (MDCT) scan• enables rapid acquisition of data sets with

accurate anatomic detail,• delivering valuable multiplanar • three-dimensional•information regarding the morphologic features•of chest injuries .•However, such rapid high resolution•imaging comes with the distinct disadvantage•of delivering higher radiation doses

•EPIDEMIOLOGY AND PATHOPHYSIOLOGY•The most common cause of morbidity andmortality in

children aged 1 to 14 years is trauma•The National Pediatric Trauma Registry reported•the incidence of major chest injury to be 6%.

second only to brain injury as a cause of pediatric•trauma-related death, with mortality rates of•15% to 25%.

•The presence of serious chest injury in a multiregional trauma patient is an indicationof

the overall severity of the child’s injuries,

•increasing the mortality 20-fold compared with

•children without chest trauma

•The demonstration of clinically silent concomitant chest injury in

•patients with known head, cervical spine, abdominal,

•or extremity injury• substantially affects the•prognosis, especially in children

•In patients with chest injury, there is multiregional involvement

•(ie, polytrauma )in 50% to 81

• .Mortality with isolated chest injury is 5%

• one additional body part involvement 25% to 29%

• with more than two regions involved is 33% to 40%.

•combination of major chest trauma and traumatic

•brain injury results in a mortality of 40% to70%.

• In polytrauma, deaths in children with•chest trauma are due to nonthoracic causes in•66% to 75% of cases.

•An age-based classification of the causes of•major chest trauma shows that infants and•toddlers (0–4 years) are usually passive victims of•child abuse and motor vehicle accidents.• Schoolgoingchildren (5–9 years) sustain injuries as•pedestrians .•Older children (10–17 years) suffer•transport-related injuries with bicycles and•skateboards.

•Boys tend to participate in riskier activities, accounting

•for a male to female ratio for chest injury between•2.6 and 3.0• Blunt chest trauma is about six timesas common as

penetrating chest injury• .Penetratin g injury occurs almost exclusively in

teenagers,typically because of stab wounds or gun•shots.

•Of fatalities associated with blunt chest•injury, only 14% are due to the chest injury;

•whereas the cause of death in patients with penetratingchest injury is directly attributable

to this•injury in 97% of cases

•Rib fractures, flail chest, aortic injury, and diaphragmaticrupture are more common in

adults,

•whereas pulmonary contusion, pneumothorax,

•and intrathoracic injury without bony injury•predominate in children

•The differing pattern of injury may be explained by the anatomic and physiologic differences

between children and adults.•The trachea is relatively narrow, short, and more

readily compressible in children, so that small•changes in airway caliber from external

compression•or inhaled foreign body may result in respiratory

compromise that is more significant

•children have higher metabolic rates and consume more oxygen per kilogram

bodyweight than adults consume•

• This results ina greater vulnerability to develop rapid hypoxia in the context of major

chest trauma.

•Injuriey from seatbelts, ejection from a car restraining device, or airbag deployment often

have unique•features that can be explained by poor

adjustment•of these devices to variable pediatric sizes and•proportions.

•In general, the pediatric body more flexible, lighter, and proportioned differently than the mature

individual, leading to unique patterns of injury.

• In adults, whose inflexible ribcages•are more likely to fracture• ,more energy is absorbed by the chest wall• and there is relative sparing of the underlying soft-

tissues

•Pulmonary contusionsand pneumothorax are more common in children,

•with comparatively fewer rib fractures

• .•Therefore,imaging protocols developed for adults

do•not necessarily apply to children of all age

groups.

•Radiography•Upright frontal and lateral chest• .•polytrauma setting, supine radiographs need for

patient immobilization.

•Attention to technical factors such as•proper collimation and adequate exposure factors•to optimally demonstrate skeletal structures, lung•parenchyma, and mediastinal contours (such as•paraspinal lines) is important

•Ultrasound•Bedside ultrasonography of the lower chest may•be combined with (FAST) examination of the•abdomen.• Once pleural fluid is encountered,•it is important to screen the entire pleural space,not just the lung bases• .Lower frequency (3.5–7MHz) sector transducers can be used for initial•overview through intercostal and subcostal scanning•,•whereas higher frequency (10–12.5 MHz)linear transducers provide for

more detail in the near field, before marking for needle placement•.•For certain indications, such as the search for an occult pneumothorax or

a hemopericardium,employ an anterior approach.

•CT Scan•Once the decision to perform a CT scan has been•made, minimize radiation dosewhile obtaining a diagnostic study .•On multidetecto r scanners, the authors use a kV of 80 to120 and•mA adjusted to both patient weight and age.•More recently, we have implemented automatic•longitudinal dose adjustment based on the•measured attenuation on the scanogram and•preset noise levels that are adapted to the•patient’s age, weight, and clinical indication.• Radiation•dose can be further lowered by novel iterative•image reconstruction techniques that reduce•noise• All studies are preferably obtained with•single-phase CT angiography technique, including•(1 )the use of a power injector, (2) rapid bolus injection,•(3 )scan acquisition initiated 20 seconds after •( 4 )The shortest available tube-rotation time and the fastest•available table speed.

•Skeletal Injurythe rib fracture rate is as low as 1% to 2%

However, it rises substantially in the context of major pediatric chest trauma to 30% to 60%.

Seventy percent of children with two or more rib fractures had multisystem injuries, compared to

12% of children with a single fractured rib. The sites of rib fractures in children differ from

those in adults, being more often posterior than lateral

•A flail chest is rare in children, with a rate approximately1%.

• Fractures of the lower three ribs are associated with hepatic and splenic injuries

•.• It is rarely the rib fractures, but predominantly

the associated injuries, that determine the mortality of children with chest trauma

•Rib fractures in the0 to 3 year old age group are the result of childabuse in 39% to 80% of cases.

• Rib fracturesare found in 5% to 27% of abused children

• the only skeletal manifestation in 29%.•Multiple aligned posterior rib fractures in a child

less than 3 years has a positive predictive value of 95% for child abuse,

• which rises to 100% in the absence of a clear history of major trauma or underlying metabolic

condition predisposing to fractures.

•Acute nondisplaced rib fractures are notoriously•difficult to identify on anteroposterior (AP) chest•radiographs (Fig. 1A)• .With the exception of suspected child abuse, multiple

radiographic projections in the fracture are not routinely indicated, as accurate identification does not

typically alter management•.•A CT scan is capable of more reliably

detectingnondisplaced fractures search of a suspected isolated rib

•increased sensitivity of a CT scan, only those rib fractures that were seen on radiography predicted the development of respiratory failure.

• In suspected child abuse, acute nondisplaced rib fractures are best detected with skeletal scintigraphy

• However, owing to the delay in clinical•presentation that is typical in child abuse, healing•fractures with callus (see Fig. 1B) are more•prevalent and these are usually well seen on skeletal•surveys, especially when supplemented by oblique•Views• .For these reasons, the skeletal survey•in combination with scintigraphy when indicated•continues to be the standard of care for the evaluation•of suspected child abuse.

•Fig. 1. Rib fractures in child abuse. A 3-month-old infant with Down syndrome and congenital heart

disease, who•presented to the emergency room with mild

congestive heart failure. (A) Left lateral rib fracture (arrow) was not

•initially detected. Upon return 5 weeks later, multiple healing rib fractures were seen (B), and the

child was•placed into protective custody.

•Fractures of the upper three ribs signify high energy impact and are often associated with fractures in the

shoulder girdle and vascular injury.•Scapular and clavicular fractures (Fig. 2) and•posterior sternoclavicular dislocations (Fig. 3),•are often seen in high-impact motor vehicle accidents•involving a shoulder seatbelt. They are also associated

with a high incidence of vascular and cardiac injury.• Sternal fractures or segmental dislocations are more

commonly associated with child abuse but may occur with other forms ofchest trauma

•Fig. 2. Polytrauma. A 16-year-old girl who was involved in a high-speed motorcycle accident. (A) Chest radiograph

•upon admission shows large, left-sided tension pneumothorax and bilateral clavicular fractures (arrows).

•(B )Repeat radiograph after bilateral chest tube insertion demonstrates decompression of left tension pneumothorax,

•but interval development of a moderately sized, right-sided pneumothorax (note deep sulcus sign),•despite presence of a chest tube. Note extensive chest wall emphysema, right greater than left,

and again the•bilateral clavicular fractures (arrows). Corresponding findings on coronal (C) and axial (D–G) CT

scan images.•Additional findings on CT scanning were a liver laceration (arrow in C, black arrow in G), a

nondisplaced, left•posterior rib fracture (arrow in D), extensive pulmonary contusion and several right-sided lung

lacerations•(arrows in E )and a right-sided hemopneumothorax (fluid levels in F [arrow] and G [white arrow]).

The patient•made a rapid and complete recovery without the need for surgery