. Trauma to the pediatric chest, 1-isolation 2-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 Injury the 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