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"Introduction to Pediatric Chest Radiography" by George Taylor for OPENPediatrics

Mar 23, 2024
Introduction to Pediatric Chest Radiography, by Dr. George Taylor. Hello. My name is George Taylor. I'm from the Department of Radiology at Boston Children's Hospital. And today I wanted to talk about an

introduction

to

pediatric

chest

x-ray interpretation, focusing especially on how children differ from adults and testing a systematic approach to

pediatric

chest

x-ray evaluation. Now, why are children so different from adults? Well, in addition to the enormous size differences that occur with maturation, there is also a tremendous change in the child's body. And those developmental changes are reflected on the pediatric chest x-ray. For example, a normal two-month-old child would have a relatively large thymus in proportion to the chest.
introduction to pediatric chest radiography by george taylor for openpediatrics
And he can take almost half of the hemithorax and still be normal. On the other hand, by seven months of age, the thymus has become much smaller in proportion to the chest x-ray. And at 16 years old, you can barely see the normal thymus. So if you have a 16-year-old with a large anterior mediastinal mass, like the x-ray on the screen, in a child who has neurofibromatosis, this would be very abnormal at that age and not so abnormal at a two-month-old. So let's start with a systematic approach to chest x-ray. We will observe the lung parenchyma, the pulmonary vasculature, the airways and mediastinum, the heart and also the bone abnormalities.
introduction to pediatric chest radiography by george taylor for openpediatrics

More Interesting Facts About,

introduction to pediatric chest radiography by george taylor for openpediatrics...

Parenchyma and pulmonary vasculature. Let's start with the lungs. The factors that affect lung density are mainly lung inflation, pulmonary vascularity, the lung parenchyma itself and then the air or pleural fluid that covers it. Here we have a 14-month-old boy who is coughing and wheezing. And the initial frontal chest x-ray shows diffuse, hazy opacification of both lungs that can mimic overwhelming pneumonia. But you'll notice that there are only seven posterior ribs of inflation. An x-ray obtained two minutes later shows marked improvement in the opacification of both lungs. And so you can see that lung hypoinflation can noticeably change the appearance of the lungs, especially in a smaller baby.
introduction to pediatric chest radiography by george taylor for openpediatrics
Here is a two-year-old boy with new onset stridor. We can see an asymmetry in the density of the lungs, with the left hemithorax actually looking much brighter than the right side. And if you notice too, the size of the pulmonary vessels is very different on the left side (lower) compared to the normal right side. This is a child who aspirated a foreign body into the left bronchus with air trapping and excessive inflation of the left lung and associated decrease in pulmonary vascularity. Therefore, it is important to look for asymmetry in the pediatric lung. Here are two other conditions, two other situations in which the hemithorax can look much brighter.
introduction to pediatric chest radiography by george taylor for openpediatrics
Both babies have pneumothorax. The baby on the left side of the screen has a medial and anterior pneumothorax. And the baby on the right side of the screen mainly has a medial pneumothorax. Unlike adults, where pneumothorax occurs more laterally to the lungs, infants tend to collect pleural air in the medial and anterior location. Because they are almost always in a supine position. And the lungs are relatively rigid, allowing them to only fall backward, rather than receding toward the center, toward the mediastinum. However, focal parenchymal anomalies are also very important in pediatrics. This seven-year-old boy with cough and fever has a retrocardiac density that is also seen above the spine.
This is round pneumonia, which is a bacterial pneumonia that occurs almost exclusively in children under five years of age, where the pneumonia has a massive appearance due to poor development of the collateral airways. And that's why pneumonia can look a lot like a different mass than in adults. Here's another child who has a cough and fever and has pneumonia on the right side. We can see that lung density is markedly different on the right side compared to the left. In this situation we see that the lung can only be seen on the medial aspect of the right hemithorax.
And the pleural fluid represents the density lateral to the thorax. And on the lateral x-ray we can only see a hemidiaphragm, which suggests that this child has a pleural effusion in addition to pneumonia. Airway and mediastinum. Now let's consider the airways. We need to look at its position, its caliber and the possibility of displacement of the airway due to abnormal structures. It is very important to know that the airways in a young child and baby are very mobile and during expiration the trachea can bend almost up to 90 degrees, as can be seen in the frontal and lateral view on a normal expiratory x-ray.
The other two features to consider in the trachea are that the tracheal air column should be seen in the frontal view from the thoracic inlet to the bifurcation of the trachea. And on the side, the course of the trachea should be a nice smooth posterior curve that mimics the vertebral bodies of the thorax. Here is a child where these characteristics are not present. This two-year-old presents with new wheezing and we immediately see that the mediastinum is too wide for a two-year-old. If you remember the first images we showed, the thymus in a normal child at this age should be much, much smaller.
So this is a wide mediastinum which is abnormal. The second characteristic is that in the frontal x-ray we cannot see the column of air from the trachea to the bronchi. We lose it in the middle part of the chest. In the lateral view, we can see that the trachea is not only markedly narrowed at the thoracic inlet, but is also displaced anteriorly by a posterior structure. So in this situation, we have to think about the things that normally live behind the windpipe. And these would be the esophagus and/or lymph nodes. So because this happened so acutely, we may... we are concerned about ingestion of a foreign body with an abscess.
Well, then we did a barium swallow and upper gastrointestinal tract which showed that this child had ingested a sharp, plastic foreign body that had caused perforation of the esophagus and a periesophageal abscess that displaced and compressed the trachea forward. Therefore, it is absolutely necessary to consider foreign bodies in the appropriate age group, between 6 months and approximately 2.2 1/2 years of age. Here is another child who has an airway abnormality. You can see that the trachea, instead of being slightly to the right of the midline, is to the left of the midline. Normally, the aorta, being on the left side, minimally displaces the trachea to the right side.
In this child we see a right aortic arch and a slight narrowing of the trachea. This situation may be associated with an asymptomatic right aortic arch and vascular ring. A CT scan of this child shows a normal caliber trachea in the upper image and a moderate narrowing of the trachea in the lower image, caused by a right aortic arch and the aberrant left subclavian artery compressing the trachea posteriorly. The other part of the mediastinum that is very important to evaluate in children is the thymus and the possibility of adenopathy. As we have seen before, the size of the thymus can vary dramatically with age, and adenopathy in children is much more common caused by inflammatory or infectious causes than in adults.
Here we have a two-month-old baby who presents with a cough and has a large anterior mediastinal mass. But if we look closer at the frontal film, we can see through the mass on the right side, being able to see normal lung markings behind it. And in the lateral x-ray we can see a normal trachea with normal caliber and filling of the retrosternal air space. On closer inspection of the left chest, we can see a scalloped appearance of this anterior mediastinal mass, and scalloping occurs whenever an anterior rib crosses it. And this is very characteristic of a normal thymus, which is very fatty and is displaced by the normal structures.
Now, the next four images that I will show are all of children who have opacity in the right upper lobe, and we will go over the differences between a normal structure and those that are pathological. The image on the left side of the screen, we have seen before and it is a normal scam. Its characteristics are that we can see a nice and defined lower border, without atelectasis of the lower lung or behind it. We can see through it and see normal lung structures behind it. And if you notice the trachea, this normal thymus does not displace or compress it.
On the other hand, on the right side we have a much denser mass that is adjacent to the minor fissure of the right lung. We can see a very sharp edge and we can't see any lung marks behind it. And the trachea is slightly displaced towards this child. This is a child with pneumonia and sometimes we will be able to see air bronchograms in the very dense area of ​​a pacified lung. In this second pair, we have a right upper lobe density on the chest x-ray on the left side of the screen. But unlike the other two, there is elevation of the minor fissure, as shown by the arrow, and we can see patchy air bronchograms of that right upper lobe, and also association of the displacement of the trachea towards this lesion.
This is right upper lobe atelectasis. And in the last case, we see a nodular density in the right upper lobe with displacement of the trachea away from the mass, and a relatively dense-appearing mass. This child has a neuroblastoma. I have shown four different right upper lobe lesions that have different characteristics that can help us distinguish them from each other. Heart. Now let's look at the heart. We often talk about a normal cardiothymic silhouette in children instead of a cardiac silhouette because the thymus can be so large that it will encompass the heart and reach into the diaphragms.
Thus, the heart shadow, especially in young children, is composed of both the heart and the thymus. It is very difficult in young children to determine specific chamber enlargement because the heart is relatively large in proportion to the surrounding thorax. And finally, we have a normal double ear shadow which is a normal finding rather than an abnormal finding in adults. Here we have a five-year-old girl who presents with a cough and has a prominent left auricular shadow, as shown with the arrows. This is a completely normal finding compared to adults, where prominence of the left atrial shadow may be a pathological finding.
Bone anomalies. Finally, a look at the skeletal system is very important when performing a chest x-ray, especially if we are looking for fractures for erosions and absence of normal bone structures. Here we have a nine-month-old girl who fell out of her bed. And initially the heart appears normal. The trachea and mediastinum are normal. And yet, when we look at the ribs on the left side, we can see that there are multiple posterolateral rib fractures, as shown by the arrows. Fractures of the posterior and lateral ribs in infants younger than six months are of great concern for non-accidental trauma.
Therefore, these are very important findings on chest

radiography

and often require oblique images for better evaluation. Here, another child who presents with irritability at two years of age. We see what initially appears to be a normal chest x-ray. But if we pay more attention to the eleventh right rib, we see that the density of the ribs is patterned, irregular and different from the other ribs. Here, a close-up of that rib shows a rib that is sclerotic and eroded by an overlying neuroblastoma. These are very important but often subtle findings in the pediatric chest. So we've covered a systematic approach to the chest in children where we look at the lung parenchyma, pulmonary vasculature, airways and mediastinum, heart, and bone abnormalities.
These are some final points I would like to leave you with. First, look at the symmetry of the lungs to determine lung density and vascularity. Second, be sure to look at the lung behind the heart because it is a favorite place for pneumonia to hide. Be sure to pay attention to the size in the position of the trachea, bones and soft tissues. And finally, ask for help if you have any concerns. Thank you. Help us improve the content by giving us some feedback.

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