Nonskeletal Pediatric Imaging





Pediatric musculoskeletal imaging was covered in a special section at the end of Chapter 8 . Congenital cardiac lesions were covered in Chapter 5 . Table 9.1 shows the appropriate imaging tests for common pediatric problems.



TABLE 9.1

Imaging of Pediatric Problems

































































































































































































Suspected Problems Imaging Tests of Choice
Neonatal hydrocephalus or intracranial hemorrhage Cranial US
Seizure
Neonatal Cranial US
Uncomplicated febrile seizure No imaging needed
Neurologic deficit, partially unresponsive to therapy, new without obvious provoking factor MRI without contrast
Posttrauma CT head without contrast
Partial, generalized, intractable, or refractory seizure MRI of head without contrast
Ataxia MRI with and without contrast
Headache
Isolated, no neurologic findings No imaging needed
Isolated, with neurologic signs CT without contrast or MRI
Acute “thunderclap” headache CT without contrast
Migraine without neurologic signs No imaging needed
Head injury
Acute, mild, GCS > 13, without neurologic findings or high-risk factors Imaging very low yield
Acute, mild to moderate, < 2 years of age CT without contrast
Acute, penetrating, or moderate to severe CT without contrast
Acute, suspected skull fracture or suspected nonaccidental trauma CT without contrast
Subacute, cognitive or neurologic findings MRI without contrast
Sinusitis
Uncomplicated, acute No imaging needed
Recurrent, unresponsive, chronic CT of sinuses without contrast
Suspected orbital or intracranial complications or invasive fungal CT with IV contrast or MRI without and with IV contrast
Croup or epiglottitis Lateral soft tissue view of neck
Suspected inhaled foreign body Inspiration or expiration or decubitus chest
Difficulty breathing Chest x-ray
Fever
Without obvious source, no respiratory symptoms Chest x-ray, low yield
Neonatal or respiratory symptoms or increased WBC count Chest x-ray
Esophageal atresia or tracheoesophageal fistula Lateral radiograph with soft feeding tube in place
Asthma
Uncomplicated No imaging needed
Poor response to therapy, complicated Chest x-ray
Suspected pneumonia Chest x-ray
Congenital heart disease or congestive heart failure Chest x-ray, echocardiogram
Gastroesophageal reflux (nonbilious vomiting) Barium swallow or nuclear medicine reflux study
Vomiting (recurrent, 0–3 months of age) X-ray and UGI series
Pyloric stenosis or new-onset, nonbilious vomiting, < 3 months of age Ultrasound
Duodenal atresia or stenosis Plain x-ray (use air as contrast)
Midgut volvulus UGI series
Meconium ileus Plain x-ray and meglumine diatrizoate (Gastrografin) enema
Appendicitis CT with IV contrast or US (if experienced operator is available)
Intussusception Plain x-ray followed by reduction using air or Gastrografin enema
Necrotizing enterocolitis Plain x-ray of abdomen and possible left lateral decubitus views (to look for free air)
Crohn disease CT with IV contrast or CT enterography
Hirschsprung disease Barium or Gastrografin enema
Biliary atresia or neonatal hepatitis Nuclear medicine hepatobiliary scan
Abdominal mass Plain x-ray of abdomen and ultrasound or CT
Meckel diverticulum Nuclear medicine, Meckel scan
Urinary tract infection (febrile and < 3 years of age or poor response to treatment) US of kidneys and bladder
Hematuria
Isolated (microscopic, nonpainful, nontraumatic without proteinuria) Imaging not usually appropriate
Isolated (nonpainful, nontraumatic with proteinuria) US of kidneys and bladder
Painful or posttrauma CT of abdomen and pelvis without contrast
Rectal bleeding See text
Child abuse X-ray bone survey, CT of head without contrast, CT of abdomen if abdominal trauma
Back pain
Uncomplicated Imaging not appropriate
With constant or night pain, radicular pain, pain > 4 weeks, or neurologic signs X ray spine area of interest; if negative, MRI of complete spine
Hip dysplasia (< 4 months of age) US of hips
Limping (up to 5 years of age) X-ray of affected extremity and hip; if concern for infection, US of hips and x-ray of pelvis
Osteomyelitis, cellulitis, or septic arthritis Plain x-ray, MRI, or three-phase nuclear medicine bone scan

CT , Computed tomography; GCS , Glasgow Coma Scale; IV , intravenous; MRI , magnetic resonance imaging; UGI , upper gastrointestinal; US , ultrasound; WBC, white blood cell.


Suspected Child Abuse


The physical examination and a history of abuse may point to obvious physical child abuse, but imaging plays a major role in detection and documentation. The injuries can involve any site but are particularly evident with fractures, as well as brain and soft tissue injuries. Fractures may be of various ages and most often involve ribs, skull, and metaphyseal and epiphyseal portions of long bones. The initial imaging workup includes an x-ray skeletal survey and computed tomography (CT) of the head without IV contrast. A CT scan of the abdomen and pelvis or chest may be needed based on the clinical examination.




Head


Imaging Techniques


Imaging of the fetal and infant brain can be done by using ultrasound (US) as long as the fontanels remain open. Structures that can normally be visualized include the lateral ventricles, choroid plexus, thalamus, temporal lobes, and posterior fossa ( Fig. 9.1 ). The two most common indications for US of baby heads are (1) evaluation of ventricular enlargement (hydrocephalus) and (2) hemorrhage, either within the parenchyma of the brain or within the ventricles ( Fig. 9.2 ). The major advantages of US in this application are that the imaging can be done in the neonatal intensive care unit and ionizing radiation is not used. This is important, because these studies are repeated multiple times for continuing evaluation. If the fontanels are closed, CT is usually used for the evaluation of suspected hydrocephalus or hemorrhage.




Fig. 9.1


Ultrasound of Normal Neonatal Head.

A sagittal view obtained through an open fontanel clearly shows the frontal lobe (FL) , lateral ventricle (LV) , thalamus (Th) , temporal lobe (TL) , and choroid plexus (CP) .

Ant, Anterior; Post, posterior.



Fig. 9.2


Ultrasound of Abnormal Neonatal Head.

(A) Sagittal view of the brain in a neonate with hydrocephalus. A dilated lateral ventricle (LV) is seen, as well as the shunt (Sh) catheter. (B) Intraparenchymal hemorrhage. A sagittal view of the brain in a different infant shows a normal-sized lateral ventricle but an area of increased echoes representing hemorrhage (H) within the substance of the brain.

Ant, Anterior; Post, posterior.


Brain tumors in children are evaluated by CT or magnetic resonance imaging (MRI). With MRI, sedation is necessary, and pediatric monitoring of respiration and other functions in a very high magnetic field is difficult. CT scanning is easier to perform. About half of brain tumors in children are astrocytomas; medulloblastomas (20%), ependymomas (10%), and craniopharyngiomas (5%) are less common.


Trauma


Head trauma and the appropriate imaging studies are presented in Chapter 2 and in Table 9.1 . In general, following significant acute head trauma in a child, a noncontrast CT scan is the procedure of choice. This will reveal skull fractures and evidence of bleeding. Subacute injuries with neurologic or cognitive problems usually will have a noncontrast MRI.


Headache


Headaches are common in childhood. They may be primary (e.g., migraine, tension, cluster, exertional, cough headaches) or secondary (e.g., due to head or neck trauma, intracranial pathology, infection, thunderclap headache). MRI or CT imaging has very low yield for primary headaches but is indicated for secondary headache evaluation, especially with positive neurologic signs or increased intracranial pressure.


Childhood Seizures


Seizures may be provoked by infection, trauma, toxins, metabolic abnormality, tumor, hypoxia, cerebrovascular disease, cerebral malformation, or congenital abnormality. They also may occur without obvious cause. Neonatal seizures (usually due to hypoxic ischemic encephalopathy) typically occur in the first 7 days after birth and are evaluated with cranial US. Febrile seizures usually occur between the ages of 6 months and 4 years, and most are generalized tonic-clonic seizures. Imaging is not recommended for simple febrile seizures lasting less than 15 minutes and not recurring within 24 hours. CT or MRI may be indicated in selected patients with complex febrile seizures. Imaging is recommended for children with new-onset seizures who have experienced head trauma or partial seizures and for those who have an abnormal neurologic examination or electroencephalogram. MRI is the usual imaging modality of choice, although noncontrast CT is used initially if intracranial hemorrhage or recent trauma is suspected. For those children with a history of seizures, imaging usually is done only if the seizures are poorly controlled or are associated with a new neurologic deficit, or to follow up known abnormalities, such as a tumor.




Neck


Croup and Epiglottitis


Lateral soft tissue views of the neck are often done for the evaluation of the pediatric airway. This is important in cases of suspected croup or epiglottitis. As you evaluate these lateral images, you should look to see that the child’s neck has been extended. In a young child, when the neck is flexed, the trachea can buckle forward, causing the appearance of a retropharyngeal mass. To avoid this artifact, simply extend the neck and lift the chin ( Fig. 9.3 ).




Fig. 9.3


Pseudoretropharyngeal Abscess.

(A) Lateral soft tissue view of the neck in a child with the neck slightly flexed shows the trachea (T) bowed forward, which suggests that a retropharyngeal soft tissue mass is present (arrows) . (B) A lateral view taken a few minutes later of the same child with the neck extended shows a normal, prevertebral, soft tissue pattern.


Acute epiglottitis usually occurs in older children (between the ages of 2 and 7 years) and most commonly is due to Haemophilus influenzae . This can be a life-threatening disease; the clinical findings are severe sore throat, high fever, a muffled voice, and stridor. Patients often can breathe more easily sitting up, and they drool because they cannot swallow. This is a true pediatric emergency. Because intubation can be necessary on very short notice, a physician should accompany the child to the x-ray department. The lateral soft tissue view of the neck shows a thickened epiglottis, often appearing bulbous (in the shape of a thumb; Fig. 9.4 ). Remember that the normal epiglottis is a delicate, thin, curved structure. Other findings include ballooning of the hypopharynx and subglottic edema in about one-fourth of cases.




Fig. 9.4


Epiglottitis.

A lateral soft tissue view of the neck shows a ballooned pharynx (Ph) with a swollen epiglottis (E) in the shape of a large thumbprint (arrows) .

T , Trachea.


Croup typically occurs in young children (between the ages of 6 months and 3 years); it usually is caused by respiratory syncytial virus (RSV). These children often have a brassy cough (like the barking of a seal) and inspiratory stridor. Occasionally the airway may have enough edema that placement of an artificial airway is necessary. The findings on the lateral view are marked ballooning of the pharynx and hypopharynx. On the anteroposterior (AP) view, the upper portion of the trachea is shaped like a steeple ( Fig. 9.5 ). The steeple sign, caused by subglottic edema, is not pathognomonic because it also can occur in some children who have epiglottitis.




Fig. 9.5


Croup.

(A) In a child with a barking cough, a lateral soft tissue view of the neck demonstrates a markedly ballooned pharynx (Ph) . (B) An anteroposterior view of the neck shows a steeple-shaped trachea (T; arrows) caused by subglottic edema.




Chest


Normal Anatomy and Imaging


One of the major differences between the normal chest of an adult or child and a neonate is the presence of the thymus. It is routinely identified on chest x-rays from birth to approximately age 2 years. The thymus is usually seen as a widening of the soft tissues of the upper mediastinum, although occasionally it may appear to project out into the lung (known as the sail sign ; Fig. 9.6 ). Some people mistakenly think that the sail sign is an indication that a pneumothorax is present, but this is not true.




Fig. 9.6


Normal Thymic Shadow.

A posteroanterior view of the chest shows a prominent thymic shadow (arrows) . Sometimes referred to as the sail sign , this is a normal finding.


Imaging of the chest in infants and children can be difficult because of their uncooperative nature, especially when they are sick. In neonates, portable x-rays are usually obtained in the intensive care unit with the child in a supine AP projection. Somewhat older children can be placed in a holder or restrained with Velcro straps while an image is obtained. In most of these instances, the image is taken randomly with respect to inspiration and expiration. Amazingly enough, hypoinflation of the chest is usually not a problem in the interpretation of pediatric chest x-rays.


Most children with pneumonias, bronchiolitis, or reactive airway disease have hyperinflation. In most normal young children, the most superior portion of the hemidiaphragm is at the level of the posterior eighth rib. If the diaphragms are lower than this, hyperinflation should be considered, and pathology may well be present. Rotation of the patient can cause problems in interpretation. As the patient is rotated to the left, the right cardiac border projects over the spine and the right lower lobe pulmonary vessels are indistinct and can mimic an infiltrate ( Fig. 9.7 ).




Fig. 9.7


Pseudoinfiltrate Due to Poor Positioning.

(A) An anteroposterior view of the chest was obtained but is slightly rotated. This throws the heart shadow to the left and makes the right pulmonary vascularity appear prominent, creating the impression of a right middle or lower lobe infiltrate (arrows) . (B) A repeat view obtained on the same infant within 10 minutes shows that the chest is perfectly normal.


A favorite x-ray examination is the so-called babygram. This is an AP view of both the chest and the abdomen. In extremely small babies, the x-ray exposure can be adequate to visualize pulmonary vasculature, bowel gas, and skeletal structures. Conversely, if you are interested only in the chest, a chest x-ray is what should be ordered to avoid unnecessary radiation exposure.


Foreign Bodies


Foreign bodies can be either aspirated or ingested. Most foreign bodies consist of vegetable material (such as peanuts) or plastic. Remember that vegetable and plastic items are usually not visible on a plain x-ray. When a foreign body is aspirated into a bronchus, there are two possibilities. The first is that the object will become completely impacted and will not allow air to pass during inspiration and expiration. In this case, the air distally will become resorbed and post­obstructive atelectasis or a focal infiltrate with associated volume loss will be found.


The second possibility is that the object is only incompletely obstructing the bronchus. This occurs because, during inspiration, the bronchus becomes larger in diameter and air can pass around the object. During expiration, the bronchus becomes narrower due to pressure in the lung, and the air distal to the object cannot escape. The object acts as a ball valve. Thus, if you suspect the presence of an inhaled foreign body, be sure to order inspiration and expiration images. On the inspiration image, you may see postobstructive atelectasis, or the chest x-ray may be normal. If the chest is normal, a ball valve phenomenon may still exist, and on the expiration view, air will be trapped on the affected side, whereas the unaffected lung will decrease in volume. When this happens, a resultant shift of the mediastinum toward the normal unaffected side will be seen ( Fig. 9.8 ).


Feb 19, 2020 | Posted by in GENERAL RADIOLOGY | Comments Off on Nonskeletal Pediatric Imaging
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