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Computed Tomography in the Evaluation of Pediatric Trauma
Abstract: The objective of this article is to review the use of computed tomography (CT) for the purpose of injury evaluation in pediatric trauma patients. The relative risk of radiationinduced cancer mortality is discussed. Evidence-based indications for obtaining CT and optimization of CT scanner protocols are provided. CT use specific to pediatric trauma is discussed for the following anatomic regions: thorax, abdomen, head, spine, vascular, and musculoskeletal. Limiting unnecessary CT use by understanding when and how to order an appropriate scan in order to adequately diagnose and treat a specific injury is the most practical way for clinicians to help reduce patients’ risk of radiation.
Keywords: computed tomography; pediatric trauma; indications; risks; radiation
Computed Tomography in the Evaluation of Pediatric Trauma Drew Pierce, MD *, Kate Louise Mangona, MD*, George Bisset, MD*, Bindi Naik-Mathuria, MD†
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*Department of Pediatric Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX; †Department of Surgery, Division of Pediatric Surgery, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX. Reprint requests and correspondence: Bindi Naik-Mathuria, MD, 6701 Fannin Street, Suite 1210, Houston, TX 77005. [email protected] 1522-8401 © 2015 Published by Elsevier Inc.
omputed tomography (CT) is a form of radiography using ionizing radiation to create two- and threedimensional representations of anatomy based upon differential absorption of diagnostic range X-rays. This modality has been used in the diagnosis of pathological conditions since 1971. 1 Since that time, improvements in CT technology and availability have allowed reduced scan times, which have rendered it a highly useful tool in the evaluation of trauma patients. 2 The vast majority of the literature available in utilizing CT for evaluation of trauma patients focuses on adult patients and does not address pediatric patient care, which is notably different. 3 First, children have different injury patterns than adults and therefore have a different likelihood of having certain types of injuries than adults. Second, children are more sensitive to the effects of ionizing radiation and are more likely to be adversely affected by the overuse of CT than adult patients.
RADIATION DOSE CONSIDERATIONS The only practical radiation dose consideration in pediatric patients undergoing CT is radiation-induced cancer. 4,5 The
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specific risk is increased for younger patients and for patients who require higher doses of radiation to produce diagnostic images. The risk can also vary depending on the specific organ exposed to radiation. For an excellent practical guide on how to approach the topic of radiation risks of CT, please refer to http://www.cancer.gov/cancertopics/causes/ radiation/radiation-risks-pediatric-CT. 4 The relative risk of radiation-induced cancer mortality should also be understood at a basic level by all physicians using CT. For example, a 3 mGy average organ dose to a 10-year-old child (which would be obtained from a body CT scan) confers approximately 1/4000 increased lifetime risk of radiation-induced cancer mortality. Another way to think of this is the following: without exposure to the CT study, an otherwise healthy American child has an expected lifetime cancer mortality of 1/5 (800/4000), or 20%. After such a CT scan, this increased risk would be 801/4000 or 20.00025%. 6 Two other important concepts to remember when ordering CT studies is that: (a) radiation dose is cumulative and related cancer risk is thought to be linear (ie, a second CT study of the same dose in the child in the example raises his/her chance of lifetime cancer mortality to approximately 20.005%), and (b) the most accurate estimates of cancer mortality risk related to ionizing radiation are based on incomplete data and are therefore highly speculative. 6 The most practical ways for clinicians to help reduce their patients’ risk of cancer mortality is to limit use of CT to cases in which it is necessary to diagnose and treat a specific condition, and to limit CT use in pediatric patients to settings which have optimized protocols on the CT scanners. These protocols are put in place in order to reduce the radiation dose to the patient while still producing adequate diagnostic images. Any dedicated pediatric hospital would be expected to meet the last criterion, and any general hospital in North America with up-to-date equipment should have the resources to perform a lower dose CT using the ALARA (As Low As Reasonably Achievable) principle and recording all administered dose data (http:// www.imagegently.org/Procedures/Computed Tomography.aspx). In the event of a pediatric patient presenting to an adult trauma hospital, use of CT should be reserved for those cases where it is needed to immediately stabilize the patient before transferring to a pediatric center. If the patient is clinically stable and a transfer is pending, CT use should be directed by the accepting pediatric trauma experts.
“Pan-scanning” refers to a whole body CT, or at least one including the head, neck, chest and abdomen. The use of pan-scanning has increased over the past 30 years for the evaluation of trauma patients. It has shown efficacy in reducing mortality for adult patients in certain circumstances. 7 Despite this evidence in adults, pan-scanning for pediatric trauma without careful clinical examination of each anatomic region is never recommended. This methodology has not been validated scientifically, and the only thing certain about its use is that it will cause harm if applied broadly. Unfortunately, pan-scanning still occurs frequently in referring, non-pediatric hospitals prior to transfer to a pediatric trauma center.
THORACIC TRAUMA Chest CT has demonstrated the ability to identify numerous blunt trauma-related injuries in pediatric patients, many of which may not be visible on a radiograph. 8 Despite this, studies have shown that radiographically occult injuries rarely, if ever, change management. For instance, a chest radiograph will provide enough information regarding pulmonary contusions, pneumothorax, hemothorax, and rib fractures, and management will not be changed by obtaining a CT. Although no currently published guidelines exist to assist clinicians on the decision of when to request CT exams for blunt trauma in the United States, the published guidelines of the English Royal College of Radiology state that CT can be obviated in blunt trauma patients in whom the chest radiograph is normal, and if the patient is conscious and clinically stable. 9–12 CT is definitely recommended for cases of penetrating thoracic trauma or concern for a vascular injury such as an aortic dissection (based on a widened mediastinum on chest radiograph, or due to a concerning mechanism). Intravenous (IV) contrast should be utilized if there is concern for an underlying vascular injury. 13 (Figure 1). Aortic injuries are uncommon but highly lethal injuries in children presenting with blunt trauma. 14 In the cases where children survive the events prior to hospitalization, mortality remains significantly higher than in adults, and therefore early identification of aortic injuries is extremely important. CT with angiography has shown great efficacy in identifying aortic injuries and guiding treatment; however, due to the low overall incidence of these injuries, it should not be used as a blind screening tool for every child with blunt thoracic trauma. The rule for general thoracic injuries remains valid for thoracic vascular injuries, as a normal upright chest
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Figure 1. A and B, 3D reconstruction (A) and coronal maximum intensity projection reformat (B) from contrast enhanced chest CT demonstrating a bullet fragment adjacent to the origin of the left internal carotid artery with an associated pseudoaneurysm. Also noted are left lung contusion, drainage tube, and extensive mediastinal hemorrhage.
radiograph has been shown to confer a 98% negative predictive value. 15 Chest CT should be reserved for cases where the chest radiograph is abnormal or there is an abnormally high level of clinical concern despite a normal chest radiograph. 16
ABDOMINAL TRAUMA The utility and appropriateness of CT in evaluating pediatric abdominal trauma has been extensively studied and continues to be debated. When performed, CT should always be performed with IV contrast in the portal venous phase only. The use of oral contrast is not generally recommended unless there is specific concern for a hollow viscus injury.
In a hemodynamically unstable child presenting with a blunt abdominal injury, CT should never be used if it may delay definitive treatment. In these cases, many centers will opt to evaluate with point-of-care ultrasound, or proceed directly to laparotomy. A hemodynamically stable child who has normal cognition can generally be safely screened with a careful physical examination. 17 Several physical exam signs such as tenderness or abdominal bruising (from a seatbelt or handlebar) should spur further workup with CT. Certain elevated laboratory values, in the setting of a significant mechanism, could suggest intraabdominal injury. At our institution, an abdominal trauma protocol was developed in order to streamline indications for obtaining CT for blunt trauma, and increased the rate of clinically significant CT scans from 14 to 32% (P = .03). 18 Many centers opt to use the focused assessment with sonography in trauma (FAST) technique as a screening tool to determine which patients will benefit from CT, 18 while other centers have abandoned this practice due to belief that it is insufficiently sensitive in children. 19 Regardless of these discrepant practices, FAST has been shown to be useful in certain circumstances; for instance, in a patient too unstable to take to CT who has clinical evidence of abdominal bleeding, but it should not be used to replace CT for evaluation of blunt abdominal trauma imaging. Liver and spleen lacerations are the two most common pediatric life-threatening injuries to the abdomen in blunt trauma, and the gold standard for diagnosis is contrast-enhanced CT. Each of these injuries has its respective American Association for the Surgery of Trauma (AAST) grading scale. This scale is useful in determining the extent of management, which in most instances will be conservative. The value of CT over other imaging modalities lies in the ability to detect a contrast blush, which is associated with a greater likelihood for surgical intervention in pediatric patients. 20 Additionally, CT can help to determine whether embolization may be a valid option to stop active bleeding in order to avoid a life- or organ-threatening operation. (Figure 2). Pancreatic injuries are relatively rare, but CT has shown great value in both detecting and helping with management algorithms. 21 The main considerations in pancreatic injuries are laceration of the pancreatic parenchyma and of the pancreatic duct, the latter of which has shown to be associated with significant complications including pseudocyst formation and requirement for surgical intervention. The likelihood of duct injury can be predicted using
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Figure 2. A, CT demonstrates a high-grade liver laceration with active extravasation from a right hepatic artery branch, which was treated with angioembolization (B). 64
two grading scales, the AAST or the Wong classification systems. 22,23 Renal injuries are known complications of blunt or penetrating abdominal trauma and may require surgical and urologic interventions. They can be reliably imaged with ultrasound, but CT is more commonly used at major trauma centers in the United States. 24 The major value CT may confer over ultrasound is the ability to visualize renal collecting system injuries with delayed phase contrast-enhanced CT. (Figure 3) These studies should normally show contrast filling the collecting systems bilaterally, and may show extravasation into the retroperitoneum (or rarely into the peritoneum) in the event of a collecting system injury. Additionally, an IV contrast-enhanced CT can identify renal infarctions, which result from laceration of segmental renal arteries. 25 There is a well-established grading scale for CT of renal trauma developed by the AAST, which has been validated and shown to be useful in predicting which patients will be most likely to benefit from surgical intervention. 26 Bladder rupture is an uncommon but welldescribed entity in both adults and children. It should be suspected in any patient with pelvic fractures adjacent to the urinary bladder, unexplained ascites or other unexplained free fluid around the bladder on imaging. If any of these findings are present, a delayed CT of the pelvis after clamping an indwelling Foley catheter or by performing cystography (CT and fluoroscopy are both
thought to be suitable) with adequate distension of the urinary bladder. The importance of accurate identification and characterization of bladder rupture is in differentiating intraperitoneal rupture from extraperitoneal rupture. This is important because intraperitoneal ruptures are associated with significant mortality and will often require surgical intervention. Conversely, extraperitoneal ruptures are most often managed non-surgically. If the diagnosis is suspected prior to performing the CT, a special protocol has been described in which two-phase imaging of the abdomen and pelvis has shown to be helpful. 27 Hollow viscus injuries are often diagnosed using CT; however, CT can be insensitive for detection of early or low-grade bowel injuries. It should ultimately be noted that a normal CT cannot completely rule out a bowel injury, which may declare itself clinically in the days after initial injury. Nevertheless, in cases where there is reasonable suspicion of an intestinal injury, CT with IV contrast is the initial study of choice. Oral contrast is usually contraindicated due to the patient’s status and need for a timely study. Rare instances where oral contrast could be helpful include patients with a high degree of suspicion for a bowel injury (such as continuous vomiting for several hours after trauma or known pneumoperitoneum). The signs of bowel injury on CT range from subtle and nonspecific (more common in less severe cases managed non-operatively) to overt findings specific for severe injury and
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complications in patients who are more likely to require operative intervention. 28 An additional helpful secondary finding on abdominal CT, which is reported to be more prevalent
Figure 4. Features of hypotension/hypoperfusion complex including enhancing bowel and adrenal glands with fluid surrounding the inferior vena cava.
Figure 3. Sagittal MIP with IV contrast in portal venous phase (A and B) and delayed coronal maximal intensity projection (MIP) (C) demonstrate a penetrating glass foreign body with associated lacerations of the spleen (B) left kidney and pancreas (C). Due to the renal injury and surrounding hematoma, a delayed phase CT was acquired which demonstrated no associated collecting system injury.
in pediatric patients, is the appearance of the “hypoperfusion/hypotension complex”, a constellation of findings including thickened enhancing bowel walls, decreased caliber of the inferior vena cava and aorta, fluid surrounding the inferior vena cava, hyperenhancing adrenal glands and relative low enhancement within the spleen and liver. This can indicate impending shock and direct clinical teams toward correction of fluid balance or blood loss to help improve chances of survival. The hypoperfusion complex has also been described in non-traumatic scenarios in adult patients. The appearance of the hypoperfusion complex overlaps that of bowel injury and clinicians and radiologists must be aware of this fact to allow appropriate patient care as the treatment of the two conditions is disparate. 29 (Figure 4) (See Figs. 4–7). The mainstay of evaluation of pelvic fractures is the pelvic radiograph. CT is recommended only if a fracture is identified on radiograph or if there is uncertainty regarding the presence of a fracture. Due to the increased likelihood of arterial injury in patients with pelvic fractures, CT with contrast is usually recommended when a pelvic fracture is identified by radiograph; a multiphasic CT is a reasonable option in this case. 30 When evaluating pelvic fractures, urethral injuries may also be visualized on pelvic CT. However; fluoroscopic retrograde urethrography is the gold standard for these injuries. It should be performed before placement of a urethral catheter in any patient who is clinically suspected to have a urethral injury, or who has suspicious findings on CT such as adjacent pelvic fractures or soft tissue laceration. 31
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A
B
C
Figure 5. A, Non-contrast CT demonstrates lens-shaped extra-axial hemorrhage along the left frontal lobe. Shape suggests epidural location. Generalized mass effect with 4 mm of rightward midline shift. B and C, Reformatted 3D images from CT depict non-depressed skull fracture vertically oriented through the left parietal bone.
HEAD TRAUMA Traumatic brain injury is the leading cause of death and disability in the pediatric population, and the estimated lethal malignancy rate from head CT radiation is between 1/1000 and 1/500. The question then becomes: when is it appropriate to order a head CT? When evaluating the need for a head CT, pediatric patients are divided into two groups: those younger than 2 years, and those 2 years and older. These two groups are then further divided into two severity categories: minor head trauma, poorly defined in the literature but considered a GCS 15 or 14; and moderate/severe head trauma, with a GCS less than or equal to 13. 32
Approximately 3 to 5% of children with minor head trauma have an abnormality on brain imaging; however, less than 1% require neurosurgical intervention. 33–36 The clinical exam and expertise of the ordering emergency center clinician should heavily influence the decision to order CT imaging. The Pediatric Emergency Care Applied Research Network (PECARN) has shown a 99.9% negative predictive value (NPV) and 96.8 % sensitivity for (the absence of) a clinically significant injury in children over the age of 2 years when confirming the following clinical findings: no sign of basilar skull fracture, no severe headache, normal mental status, no loss of consciousness, no vomiting, and no severe injury
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A
B
Figure 6. A 15 year-old male adolescent with (A) lateral C-spine X-ray showing avulsion fracture of C7 spinous process (Clay Shoveler’s) and mild anterolisthesis at C2/C3. The latter may represent pseudosubluxation in this age group. B, C-Spine CT demonstrates similar findings.
mechanism. This PECARN study is the largest prospective study performed exclusively in young patients. 34 Other retrospective studies have found similarly high sensitivity and NPV with variable specificity, including the National Institute for Health and Care Excellence guidelines; the Children's Head Injury Algorithm for the Prediction of Important Clinical Events; and the Canadian Assessment of Tomography for Childhood Head Injury. 37–40 In a patient of any age with a moderate/severe brain injury or a minor head injury with altered mental status or signs of a basilar skull fracture, either a non-contrast head CT or magnetic resonance imaging (MRI) (if readily available) is appropriate to assess for injury. Children with seemingly minor head injury accompanied by altered mental status and/or skull fracture have a 4% increased risk of traumatic brain injury; these children are considered high risk. 37 In any case of suspected non-accidental head trauma, a noncontrast head CT or MRI is indicated as well. 41 There is no role for contrast-enhanced CT in the emergent setting, as contrast adds little to no benefit, and may even confound an area of bleeding. Approximately 50% of intracranial injuries occur in the absence of skull fracture; as a result, radiographs have a debated role in emergent imaging after head trauma, and do not obviate the need for a head CT in most cases of suspected intracranial injury. Skull fractures positively corre-
Figure 7. An 8-year-old male with absent radial pulse after dog bite to right arm. IV contrast-enhanced CT angiogram in arterial phase, corona MIP reconstruction demonstrates acute right brachial arterial injury with reconstitution distally.
late with intracranial injury; however, approximately 21% of percent of skull fractures seen on head CT are missed on skull radiographs. 42,43 (Figure 5)
SPINE TRAUMA Regarding acute trauma to the spine, both the National Emergency X-Radiography Utilization Study (NEXUS) criteria (34,000 patients evaluated of which 3,065 were children) and the Canadian C-Spine Rule (CCR) group (9,000 patients evaluated) have well-respected suggestions about which patients to appropriately image; however, the evidence supporting these rules was obtained primarily in adult patients. 44 Limiting cervical spine radiation in children is of importance given the increased risk of thyroid cancer. 45 Of the children younger than 14 years in the NEXUS study, fewer than 1% with cervical spine X-rays
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actually had a cervical spinal injury (CSI), and only 4 of these were younger than 9 years. In 2001, Viccellio et al reported that the NEXUS criteria could be reliable in children as well, but should be applied with caution when caring for infants and toddlers. 46,47 The Congress of Neurological Surgeons and the American College of Radiology (ACR) have both stated that no spinal imaging is necessary if a child is: alert; communicative; and without neurological deficit, back or neck pain or distracting injury; then no spinal imaging is necessary. 48 If there is a positive physical examination finding, a cervical spine radiograph series including AP, lateral and open mouth views is diagnostic in children younger than 14 years. Since interpretation of cervical spine radiographs in children is not complicated by osteopenia or degenerative changes as in adults, radiographs can much more accurately diagnose fractures in children than in adults. 48 If a CT must be done in a child, ACR suggests limiting the coverage to the area of concern on the radiograph. 48 In reality, however, the spine series can be difficulty to obtain in younger children, and many providers are uncomfortable clinically clearing the cervical spines of pediatric trauma patients with a significant mechanism of injury. A case-control study of children younger than 16 years from the PECARN network identified 8 factors associated with cervical spine injury: altered mental status, focal neurologic findings, neck pain, torticollis, substantial torso injury, conditions predisposing to cervical spine injury, diving, and high-risk motor vehicle crash. One or more of these factors were 98% sensitive and 26% specific for cervical spine injury. 49 Although these findings are still being prospectively validated, they should be considered when creating institutional guidelines for cervical spine clearance in pediatric patients younger than 16 years. Evaluation of the cervical spine in older teenagers should be performed by CT when clinical clearance by the NEXUS criteria is not possible (similar to adult patients), as their spines have fully matured (Figure 6). There are few studies on pediatric thoracic and lumbar spine trauma in the literature; however, the ACR recommends AP and lateral radiographs of the thoracic and lumbar spine as the primary imaging study of choice when there is a suspected injury or a known cervical spine fracture. A dedicated CT of the thoracic or lumbar spine is not felt to be necessary as spinal fractures in children are not as subtle as those in adults. If a thoracic, abdominal or pelvic CT has already been
performed, derived images may also be used to evaluate the spine rather than reimaging. 48,50,51
VASCULAR TRAUMA In recent decades, conventional angiography has been the diagnostic tool clinicians chose first when concerned about traumatic injury of vessels in the neck or extremities. Conventional angiography carries drawbacks of invasiveness, increased radiation dose, limited availability and limited ability to evaluate the tissues around the vessels when compared to CT angiography (CTA). Thus, CTA has become more frequently utilized in recent years to evaluate adults and children with suspected vascular trauma. The true utility of CTA becomes apparent when a specific vascular injury is difficult to diagnose based on history and physical exam. As vascular trauma in children is rare, few studies have been performed comparing the accuracy of conventional angiography (CA) to CTA. In the adult population, CTA has gained acceptance as multiple studies have shown it to have 100% sensitivity and 100% specificity in the diagnosis of vascular trauma. 52,53 Soose et al have demonstrated a benefit of CTA in detecting occult internal carotid artery injury in pediatric patients with oropharyngeal trauma. 55 In a 2009 study by Hogan, CTA was 95% accurate in the diagnosis of penetrating vascular injuries of the neck and extremities, with 100% sensitivity and 93% specificity. 56 The most important indications for CTA or CA include abnormal Doppler pressure indices and high clinical suspicion (“hard signs” such as loss of pulse or pulsatile bleeding). 52-54,57,58 Additional “soft signs” of vascular trauma including hypotension, small hematoma (non-expansile or pulsatile), diminished or unequal pulses, neurologic deficit, history of severe hemorrhage at scene, or a fracture in proximity to a vascular structure are also indications to obtain a CTA (Figure 7).
MUSCULOSKELETAL TRAUMA When diagnosing pediatric fractures, CT is not usually indicated in the emergent setting; however, if the fracture is severe enough to warrant emergent operation, the CT often adds pre-operative value. Polytrauma patients can be difficult to properly position for diagnostic radiographs, which makes CT more optimal at evaluating suspected complex fractures, especially involving the midfoot, carpus, tibial plateau and plafond. Any extremity injury severe enough to prevent ideal positioning for sufficient radiographs likely warrants evaluation by
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CT. 59 Additionally, approximately 25% of foot fractures are missed by radiographs but found on CT. 60 Because fractures in the midfoot can be complex, a CT could be indicated if there is a strong suspicion for complex foot injury such as a Lisfranc injury or comminuted calcaneal fracture. 61 In a limping child less than 5 years old, there is almost no role for CT in the emergent setting. 62,63
SUMMARY The popular saying in pediatric medicine— “Children are not just little adults”—has a significant application in the use of CT imaging for trauma. CT is widely used in adult trauma patients, and the trend continues to move toward CT and away from other modalities in this population. In children, however, increasing evidence about the risks of radiation exposure has moved the needle in the opposite direction: away from unnecessary CT use. The role of the trauma “pan scan” should not be applied to pediatric trauma patients; instead, careful consideration should be paid to the likelihood of an injury that needs to be identified by CT, and whether other imaging modalities or other ways to exclude injuries are feasible in this vulnerable population. When necessary, CT can be extremely valuable and should be ordered using the correct protocol and the lowest radiation dose possible in order to maximize its benefit and minimize its risk.
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46. Viccellio P, Simon H, Pressman BD, et al. A prospective multicenter study of cervical spine injury in children. J Pediatr Surg 2001;108, e20. 47. Rozzelle CJ, Arabi B, Dhall SS, et al. Spinal cord injury without radiographic abnormality (SCIWORA). Neurosurgery 2013;72:227–33. 48. American College of Radiology. ACR appropriateness criteria suspected spine trauma. AHRQ National Guideline Clearinghouse; 2012. Available at: http://www.guideline.gov/content.aspx?id=37931. Accessed 10/28/15. 49. Leonard JC, Kupperman N, Olsen C, et al. Factors associated with cervical spine injury in children after blunt trauma. Ann Emerg Med 2011;58(2):145–55. 50. Mancini DJ, Burchard KW, Pekala JS. Optimal thoracic and lumbar spine imaging for trauma: are thoracic and lumbar spine reformats always indicated? J Trauma 2010;69:119–21. 51. Smith MW, Reed JD, Facco R, et al. The reliability of nonreconstructed computerized tomographic scans of the abdomen and pelvis in detecting thoracolumbar spine injuries in blunt trauma patients with altered mental status. J Bone Joint Surg 2009;91:2342–9. 52. Inaba K, Potzman J, Hunera F, et al. Multi-slice CT angiography for arterial evaluation in the injured lower extremity. J Trauma 2006;60:502–7. 53. Mirvis SE, Shanmuganathan K, Miller BH, et al. Traumatic aortic injury: diagnosis with contrast-enhanced thoracic CT– five-year experience at a major trauma center. Radiology 1996;200:413–22. 54. Cheng YF, Chen LC, Jawan B, et al. Multislice computed tomography angiography in pediatric liver transplantation. Transplantation 2003;76:353–7. 55. Soose RJ, Simons JP, Mandell DL. Evaluation and management of pediatric oropharyngeal trauma. Arch Otolaryngol Head Neck Surg 2006;132:446–51. 56. Hogan AR, Lineen EB, Perez EA, et al. Value of computed tomographic angiography in neck and extremity pediatric vascular trauma. J Pediatr Surg 2009;44:1236–41. 57. Anderson RJ, Hobson II RW, Lee BC, et al. Reduced dependency on arteriography for penetrating extremity trauma. J Trauma 1990;30:1059–65. 58. Lin PH, Dodson TF, Bush RL, et al. Surgical intervention for complications caused by femoral artery catheterization in pediatric patients. J Vasc Surg 2001;34:1071–8. 59. American College of Radiology. ACR appropriateness criteria: acute hand and wrist trauma. AHEQ National Guideline Clearinghouse; 2013. Available at: http://www.guideline.gov/ content.aspx?id=47667. Accessed 10/28/15. 60. Haapamaki VV, Kiuru MJ, Koskinen SK. Ankle and foot injuries: analysis of MDCT findings. AJR Am J Roentgenol 2004;183:615–22. 61. Bancroft LW, Kransdorf HJ, Adler R, et al. ACR appropriateness criteria acute trauma to the foot. J Am Coll Radiol 2015; 12:575–81. 62. Cutler L, Molloy A, Dhukuram V, et al. Do CT scans aid assessment of distal tibial physeal fractures? J Bone Joint Surg 2004;86:239–43. 63. Gaeta M, Minutoli F, Scribano E, et al. CT and MR imaging findings in athletes with early tibial stress injuries: comparison with bone scintigraphy findings and emphasis on cortical abnormalities. Radiology 2005;235:553–61. 64. Fallon SC, Loker MT, Hernandez J, et al. Transarterial angioembolization of a traumatic hepatic artery injury in a pediatric patient. J Pediatr Surg 2013;48:e9-12.
Keywords: computed tomography; pediatric trauma; indications; risks; radiation
Computed Tomography in the Evaluation of Pediatric Trauma Drew Pierce, MD *, Kate Louise Mangona, MD*, George Bisset, MD*, Bindi Naik-Mathuria, MD†
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*Department of Pediatric Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX; †Department of Surgery, Division of Pediatric Surgery, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX. Reprint requests and correspondence: Bindi Naik-Mathuria, MD, 6701 Fannin Street, Suite 1210, Houston, TX 77005. [email protected] 1522-8401 © 2015 Published by Elsevier Inc.
omputed tomography (CT) is a form of radiography using ionizing radiation to create two- and threedimensional representations of anatomy based upon differential absorption of diagnostic range X-rays. This modality has been used in the diagnosis of pathological conditions since 1971. 1 Since that time, improvements in CT technology and availability have allowed reduced scan times, which have rendered it a highly useful tool in the evaluation of trauma patients. 2 The vast majority of the literature available in utilizing CT for evaluation of trauma patients focuses on adult patients and does not address pediatric patient care, which is notably different. 3 First, children have different injury patterns than adults and therefore have a different likelihood of having certain types of injuries than adults. Second, children are more sensitive to the effects of ionizing radiation and are more likely to be adversely affected by the overuse of CT than adult patients.
RADIATION DOSE CONSIDERATIONS The only practical radiation dose consideration in pediatric patients undergoing CT is radiation-induced cancer. 4,5 The
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specific risk is increased for younger patients and for patients who require higher doses of radiation to produce diagnostic images. The risk can also vary depending on the specific organ exposed to radiation. For an excellent practical guide on how to approach the topic of radiation risks of CT, please refer to http://www.cancer.gov/cancertopics/causes/ radiation/radiation-risks-pediatric-CT. 4 The relative risk of radiation-induced cancer mortality should also be understood at a basic level by all physicians using CT. For example, a 3 mGy average organ dose to a 10-year-old child (which would be obtained from a body CT scan) confers approximately 1/4000 increased lifetime risk of radiation-induced cancer mortality. Another way to think of this is the following: without exposure to the CT study, an otherwise healthy American child has an expected lifetime cancer mortality of 1/5 (800/4000), or 20%. After such a CT scan, this increased risk would be 801/4000 or 20.00025%. 6 Two other important concepts to remember when ordering CT studies is that: (a) radiation dose is cumulative and related cancer risk is thought to be linear (ie, a second CT study of the same dose in the child in the example raises his/her chance of lifetime cancer mortality to approximately 20.005%), and (b) the most accurate estimates of cancer mortality risk related to ionizing radiation are based on incomplete data and are therefore highly speculative. 6 The most practical ways for clinicians to help reduce their patients’ risk of cancer mortality is to limit use of CT to cases in which it is necessary to diagnose and treat a specific condition, and to limit CT use in pediatric patients to settings which have optimized protocols on the CT scanners. These protocols are put in place in order to reduce the radiation dose to the patient while still producing adequate diagnostic images. Any dedicated pediatric hospital would be expected to meet the last criterion, and any general hospital in North America with up-to-date equipment should have the resources to perform a lower dose CT using the ALARA (As Low As Reasonably Achievable) principle and recording all administered dose data (http:// www.imagegently.org/Procedures/Computed Tomography.aspx). In the event of a pediatric patient presenting to an adult trauma hospital, use of CT should be reserved for those cases where it is needed to immediately stabilize the patient before transferring to a pediatric center. If the patient is clinically stable and a transfer is pending, CT use should be directed by the accepting pediatric trauma experts.
“Pan-scanning” refers to a whole body CT, or at least one including the head, neck, chest and abdomen. The use of pan-scanning has increased over the past 30 years for the evaluation of trauma patients. It has shown efficacy in reducing mortality for adult patients in certain circumstances. 7 Despite this evidence in adults, pan-scanning for pediatric trauma without careful clinical examination of each anatomic region is never recommended. This methodology has not been validated scientifically, and the only thing certain about its use is that it will cause harm if applied broadly. Unfortunately, pan-scanning still occurs frequently in referring, non-pediatric hospitals prior to transfer to a pediatric trauma center.
THORACIC TRAUMA Chest CT has demonstrated the ability to identify numerous blunt trauma-related injuries in pediatric patients, many of which may not be visible on a radiograph. 8 Despite this, studies have shown that radiographically occult injuries rarely, if ever, change management. For instance, a chest radiograph will provide enough information regarding pulmonary contusions, pneumothorax, hemothorax, and rib fractures, and management will not be changed by obtaining a CT. Although no currently published guidelines exist to assist clinicians on the decision of when to request CT exams for blunt trauma in the United States, the published guidelines of the English Royal College of Radiology state that CT can be obviated in blunt trauma patients in whom the chest radiograph is normal, and if the patient is conscious and clinically stable. 9–12 CT is definitely recommended for cases of penetrating thoracic trauma or concern for a vascular injury such as an aortic dissection (based on a widened mediastinum on chest radiograph, or due to a concerning mechanism). Intravenous (IV) contrast should be utilized if there is concern for an underlying vascular injury. 13 (Figure 1). Aortic injuries are uncommon but highly lethal injuries in children presenting with blunt trauma. 14 In the cases where children survive the events prior to hospitalization, mortality remains significantly higher than in adults, and therefore early identification of aortic injuries is extremely important. CT with angiography has shown great efficacy in identifying aortic injuries and guiding treatment; however, due to the low overall incidence of these injuries, it should not be used as a blind screening tool for every child with blunt thoracic trauma. The rule for general thoracic injuries remains valid for thoracic vascular injuries, as a normal upright chest
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Figure 1. A and B, 3D reconstruction (A) and coronal maximum intensity projection reformat (B) from contrast enhanced chest CT demonstrating a bullet fragment adjacent to the origin of the left internal carotid artery with an associated pseudoaneurysm. Also noted are left lung contusion, drainage tube, and extensive mediastinal hemorrhage.
radiograph has been shown to confer a 98% negative predictive value. 15 Chest CT should be reserved for cases where the chest radiograph is abnormal or there is an abnormally high level of clinical concern despite a normal chest radiograph. 16
ABDOMINAL TRAUMA The utility and appropriateness of CT in evaluating pediatric abdominal trauma has been extensively studied and continues to be debated. When performed, CT should always be performed with IV contrast in the portal venous phase only. The use of oral contrast is not generally recommended unless there is specific concern for a hollow viscus injury.
In a hemodynamically unstable child presenting with a blunt abdominal injury, CT should never be used if it may delay definitive treatment. In these cases, many centers will opt to evaluate with point-of-care ultrasound, or proceed directly to laparotomy. A hemodynamically stable child who has normal cognition can generally be safely screened with a careful physical examination. 17 Several physical exam signs such as tenderness or abdominal bruising (from a seatbelt or handlebar) should spur further workup with CT. Certain elevated laboratory values, in the setting of a significant mechanism, could suggest intraabdominal injury. At our institution, an abdominal trauma protocol was developed in order to streamline indications for obtaining CT for blunt trauma, and increased the rate of clinically significant CT scans from 14 to 32% (P = .03). 18 Many centers opt to use the focused assessment with sonography in trauma (FAST) technique as a screening tool to determine which patients will benefit from CT, 18 while other centers have abandoned this practice due to belief that it is insufficiently sensitive in children. 19 Regardless of these discrepant practices, FAST has been shown to be useful in certain circumstances; for instance, in a patient too unstable to take to CT who has clinical evidence of abdominal bleeding, but it should not be used to replace CT for evaluation of blunt abdominal trauma imaging. Liver and spleen lacerations are the two most common pediatric life-threatening injuries to the abdomen in blunt trauma, and the gold standard for diagnosis is contrast-enhanced CT. Each of these injuries has its respective American Association for the Surgery of Trauma (AAST) grading scale. This scale is useful in determining the extent of management, which in most instances will be conservative. The value of CT over other imaging modalities lies in the ability to detect a contrast blush, which is associated with a greater likelihood for surgical intervention in pediatric patients. 20 Additionally, CT can help to determine whether embolization may be a valid option to stop active bleeding in order to avoid a life- or organ-threatening operation. (Figure 2). Pancreatic injuries are relatively rare, but CT has shown great value in both detecting and helping with management algorithms. 21 The main considerations in pancreatic injuries are laceration of the pancreatic parenchyma and of the pancreatic duct, the latter of which has shown to be associated with significant complications including pseudocyst formation and requirement for surgical intervention. The likelihood of duct injury can be predicted using
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Figure 2. A, CT demonstrates a high-grade liver laceration with active extravasation from a right hepatic artery branch, which was treated with angioembolization (B). 64
two grading scales, the AAST or the Wong classification systems. 22,23 Renal injuries are known complications of blunt or penetrating abdominal trauma and may require surgical and urologic interventions. They can be reliably imaged with ultrasound, but CT is more commonly used at major trauma centers in the United States. 24 The major value CT may confer over ultrasound is the ability to visualize renal collecting system injuries with delayed phase contrast-enhanced CT. (Figure 3) These studies should normally show contrast filling the collecting systems bilaterally, and may show extravasation into the retroperitoneum (or rarely into the peritoneum) in the event of a collecting system injury. Additionally, an IV contrast-enhanced CT can identify renal infarctions, which result from laceration of segmental renal arteries. 25 There is a well-established grading scale for CT of renal trauma developed by the AAST, which has been validated and shown to be useful in predicting which patients will be most likely to benefit from surgical intervention. 26 Bladder rupture is an uncommon but welldescribed entity in both adults and children. It should be suspected in any patient with pelvic fractures adjacent to the urinary bladder, unexplained ascites or other unexplained free fluid around the bladder on imaging. If any of these findings are present, a delayed CT of the pelvis after clamping an indwelling Foley catheter or by performing cystography (CT and fluoroscopy are both
thought to be suitable) with adequate distension of the urinary bladder. The importance of accurate identification and characterization of bladder rupture is in differentiating intraperitoneal rupture from extraperitoneal rupture. This is important because intraperitoneal ruptures are associated with significant mortality and will often require surgical intervention. Conversely, extraperitoneal ruptures are most often managed non-surgically. If the diagnosis is suspected prior to performing the CT, a special protocol has been described in which two-phase imaging of the abdomen and pelvis has shown to be helpful. 27 Hollow viscus injuries are often diagnosed using CT; however, CT can be insensitive for detection of early or low-grade bowel injuries. It should ultimately be noted that a normal CT cannot completely rule out a bowel injury, which may declare itself clinically in the days after initial injury. Nevertheless, in cases where there is reasonable suspicion of an intestinal injury, CT with IV contrast is the initial study of choice. Oral contrast is usually contraindicated due to the patient’s status and need for a timely study. Rare instances where oral contrast could be helpful include patients with a high degree of suspicion for a bowel injury (such as continuous vomiting for several hours after trauma or known pneumoperitoneum). The signs of bowel injury on CT range from subtle and nonspecific (more common in less severe cases managed non-operatively) to overt findings specific for severe injury and
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complications in patients who are more likely to require operative intervention. 28 An additional helpful secondary finding on abdominal CT, which is reported to be more prevalent
Figure 4. Features of hypotension/hypoperfusion complex including enhancing bowel and adrenal glands with fluid surrounding the inferior vena cava.
Figure 3. Sagittal MIP with IV contrast in portal venous phase (A and B) and delayed coronal maximal intensity projection (MIP) (C) demonstrate a penetrating glass foreign body with associated lacerations of the spleen (B) left kidney and pancreas (C). Due to the renal injury and surrounding hematoma, a delayed phase CT was acquired which demonstrated no associated collecting system injury.
in pediatric patients, is the appearance of the “hypoperfusion/hypotension complex”, a constellation of findings including thickened enhancing bowel walls, decreased caliber of the inferior vena cava and aorta, fluid surrounding the inferior vena cava, hyperenhancing adrenal glands and relative low enhancement within the spleen and liver. This can indicate impending shock and direct clinical teams toward correction of fluid balance or blood loss to help improve chances of survival. The hypoperfusion complex has also been described in non-traumatic scenarios in adult patients. The appearance of the hypoperfusion complex overlaps that of bowel injury and clinicians and radiologists must be aware of this fact to allow appropriate patient care as the treatment of the two conditions is disparate. 29 (Figure 4) (See Figs. 4–7). The mainstay of evaluation of pelvic fractures is the pelvic radiograph. CT is recommended only if a fracture is identified on radiograph or if there is uncertainty regarding the presence of a fracture. Due to the increased likelihood of arterial injury in patients with pelvic fractures, CT with contrast is usually recommended when a pelvic fracture is identified by radiograph; a multiphasic CT is a reasonable option in this case. 30 When evaluating pelvic fractures, urethral injuries may also be visualized on pelvic CT. However; fluoroscopic retrograde urethrography is the gold standard for these injuries. It should be performed before placement of a urethral catheter in any patient who is clinically suspected to have a urethral injury, or who has suspicious findings on CT such as adjacent pelvic fractures or soft tissue laceration. 31
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A
B
C
Figure 5. A, Non-contrast CT demonstrates lens-shaped extra-axial hemorrhage along the left frontal lobe. Shape suggests epidural location. Generalized mass effect with 4 mm of rightward midline shift. B and C, Reformatted 3D images from CT depict non-depressed skull fracture vertically oriented through the left parietal bone.
HEAD TRAUMA Traumatic brain injury is the leading cause of death and disability in the pediatric population, and the estimated lethal malignancy rate from head CT radiation is between 1/1000 and 1/500. The question then becomes: when is it appropriate to order a head CT? When evaluating the need for a head CT, pediatric patients are divided into two groups: those younger than 2 years, and those 2 years and older. These two groups are then further divided into two severity categories: minor head trauma, poorly defined in the literature but considered a GCS 15 or 14; and moderate/severe head trauma, with a GCS less than or equal to 13. 32
Approximately 3 to 5% of children with minor head trauma have an abnormality on brain imaging; however, less than 1% require neurosurgical intervention. 33–36 The clinical exam and expertise of the ordering emergency center clinician should heavily influence the decision to order CT imaging. The Pediatric Emergency Care Applied Research Network (PECARN) has shown a 99.9% negative predictive value (NPV) and 96.8 % sensitivity for (the absence of) a clinically significant injury in children over the age of 2 years when confirming the following clinical findings: no sign of basilar skull fracture, no severe headache, normal mental status, no loss of consciousness, no vomiting, and no severe injury
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A
B
Figure 6. A 15 year-old male adolescent with (A) lateral C-spine X-ray showing avulsion fracture of C7 spinous process (Clay Shoveler’s) and mild anterolisthesis at C2/C3. The latter may represent pseudosubluxation in this age group. B, C-Spine CT demonstrates similar findings.
mechanism. This PECARN study is the largest prospective study performed exclusively in young patients. 34 Other retrospective studies have found similarly high sensitivity and NPV with variable specificity, including the National Institute for Health and Care Excellence guidelines; the Children's Head Injury Algorithm for the Prediction of Important Clinical Events; and the Canadian Assessment of Tomography for Childhood Head Injury. 37–40 In a patient of any age with a moderate/severe brain injury or a minor head injury with altered mental status or signs of a basilar skull fracture, either a non-contrast head CT or magnetic resonance imaging (MRI) (if readily available) is appropriate to assess for injury. Children with seemingly minor head injury accompanied by altered mental status and/or skull fracture have a 4% increased risk of traumatic brain injury; these children are considered high risk. 37 In any case of suspected non-accidental head trauma, a noncontrast head CT or MRI is indicated as well. 41 There is no role for contrast-enhanced CT in the emergent setting, as contrast adds little to no benefit, and may even confound an area of bleeding. Approximately 50% of intracranial injuries occur in the absence of skull fracture; as a result, radiographs have a debated role in emergent imaging after head trauma, and do not obviate the need for a head CT in most cases of suspected intracranial injury. Skull fractures positively corre-
Figure 7. An 8-year-old male with absent radial pulse after dog bite to right arm. IV contrast-enhanced CT angiogram in arterial phase, corona MIP reconstruction demonstrates acute right brachial arterial injury with reconstitution distally.
late with intracranial injury; however, approximately 21% of percent of skull fractures seen on head CT are missed on skull radiographs. 42,43 (Figure 5)
SPINE TRAUMA Regarding acute trauma to the spine, both the National Emergency X-Radiography Utilization Study (NEXUS) criteria (34,000 patients evaluated of which 3,065 were children) and the Canadian C-Spine Rule (CCR) group (9,000 patients evaluated) have well-respected suggestions about which patients to appropriately image; however, the evidence supporting these rules was obtained primarily in adult patients. 44 Limiting cervical spine radiation in children is of importance given the increased risk of thyroid cancer. 45 Of the children younger than 14 years in the NEXUS study, fewer than 1% with cervical spine X-rays
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actually had a cervical spinal injury (CSI), and only 4 of these were younger than 9 years. In 2001, Viccellio et al reported that the NEXUS criteria could be reliable in children as well, but should be applied with caution when caring for infants and toddlers. 46,47 The Congress of Neurological Surgeons and the American College of Radiology (ACR) have both stated that no spinal imaging is necessary if a child is: alert; communicative; and without neurological deficit, back or neck pain or distracting injury; then no spinal imaging is necessary. 48 If there is a positive physical examination finding, a cervical spine radiograph series including AP, lateral and open mouth views is diagnostic in children younger than 14 years. Since interpretation of cervical spine radiographs in children is not complicated by osteopenia or degenerative changes as in adults, radiographs can much more accurately diagnose fractures in children than in adults. 48 If a CT must be done in a child, ACR suggests limiting the coverage to the area of concern on the radiograph. 48 In reality, however, the spine series can be difficulty to obtain in younger children, and many providers are uncomfortable clinically clearing the cervical spines of pediatric trauma patients with a significant mechanism of injury. A case-control study of children younger than 16 years from the PECARN network identified 8 factors associated with cervical spine injury: altered mental status, focal neurologic findings, neck pain, torticollis, substantial torso injury, conditions predisposing to cervical spine injury, diving, and high-risk motor vehicle crash. One or more of these factors were 98% sensitive and 26% specific for cervical spine injury. 49 Although these findings are still being prospectively validated, they should be considered when creating institutional guidelines for cervical spine clearance in pediatric patients younger than 16 years. Evaluation of the cervical spine in older teenagers should be performed by CT when clinical clearance by the NEXUS criteria is not possible (similar to adult patients), as their spines have fully matured (Figure 6). There are few studies on pediatric thoracic and lumbar spine trauma in the literature; however, the ACR recommends AP and lateral radiographs of the thoracic and lumbar spine as the primary imaging study of choice when there is a suspected injury or a known cervical spine fracture. A dedicated CT of the thoracic or lumbar spine is not felt to be necessary as spinal fractures in children are not as subtle as those in adults. If a thoracic, abdominal or pelvic CT has already been
performed, derived images may also be used to evaluate the spine rather than reimaging. 48,50,51
VASCULAR TRAUMA In recent decades, conventional angiography has been the diagnostic tool clinicians chose first when concerned about traumatic injury of vessels in the neck or extremities. Conventional angiography carries drawbacks of invasiveness, increased radiation dose, limited availability and limited ability to evaluate the tissues around the vessels when compared to CT angiography (CTA). Thus, CTA has become more frequently utilized in recent years to evaluate adults and children with suspected vascular trauma. The true utility of CTA becomes apparent when a specific vascular injury is difficult to diagnose based on history and physical exam. As vascular trauma in children is rare, few studies have been performed comparing the accuracy of conventional angiography (CA) to CTA. In the adult population, CTA has gained acceptance as multiple studies have shown it to have 100% sensitivity and 100% specificity in the diagnosis of vascular trauma. 52,53 Soose et al have demonstrated a benefit of CTA in detecting occult internal carotid artery injury in pediatric patients with oropharyngeal trauma. 55 In a 2009 study by Hogan, CTA was 95% accurate in the diagnosis of penetrating vascular injuries of the neck and extremities, with 100% sensitivity and 93% specificity. 56 The most important indications for CTA or CA include abnormal Doppler pressure indices and high clinical suspicion (“hard signs” such as loss of pulse or pulsatile bleeding). 52-54,57,58 Additional “soft signs” of vascular trauma including hypotension, small hematoma (non-expansile or pulsatile), diminished or unequal pulses, neurologic deficit, history of severe hemorrhage at scene, or a fracture in proximity to a vascular structure are also indications to obtain a CTA (Figure 7).
MUSCULOSKELETAL TRAUMA When diagnosing pediatric fractures, CT is not usually indicated in the emergent setting; however, if the fracture is severe enough to warrant emergent operation, the CT often adds pre-operative value. Polytrauma patients can be difficult to properly position for diagnostic radiographs, which makes CT more optimal at evaluating suspected complex fractures, especially involving the midfoot, carpus, tibial plateau and plafond. Any extremity injury severe enough to prevent ideal positioning for sufficient radiographs likely warrants evaluation by
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CT. 59 Additionally, approximately 25% of foot fractures are missed by radiographs but found on CT. 60 Because fractures in the midfoot can be complex, a CT could be indicated if there is a strong suspicion for complex foot injury such as a Lisfranc injury or comminuted calcaneal fracture. 61 In a limping child less than 5 years old, there is almost no role for CT in the emergent setting. 62,63
SUMMARY The popular saying in pediatric medicine— “Children are not just little adults”—has a significant application in the use of CT imaging for trauma. CT is widely used in adult trauma patients, and the trend continues to move toward CT and away from other modalities in this population. In children, however, increasing evidence about the risks of radiation exposure has moved the needle in the opposite direction: away from unnecessary CT use. The role of the trauma “pan scan” should not be applied to pediatric trauma patients; instead, careful consideration should be paid to the likelihood of an injury that needs to be identified by CT, and whether other imaging modalities or other ways to exclude injuries are feasible in this vulnerable population. When necessary, CT can be extremely valuable and should be ordered using the correct protocol and the lowest radiation dose possible in order to maximize its benefit and minimize its risk.
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