“Introduction to Pediatric Chest Radiography” by George Taylor for OPENPediatrics
31
August

By Adem Lewis / in , , , , , , , , , , , , , , , /


Introduction to Pediatric Chest Radiography,
by Dr. George Taylor. Hello. My name is George Taylor. I’m from
the Department of Radiology in Boston Children’s Hospital. And today, I wanted to talk about
an introduction to the interpretation of the pediatric chest x-ray with a special focus
on how children are different than adults and trying a systematic approach to the evaluation
of the pediatric chest. Now why are kids so different than adults?
Well, besides the tremendous size differences that happen with maturation, there is also
a tremendous change in the body of the child. And those developmental changes are reflected
on the pediatric chest x-ray. For example, a normal two-month-old would have a relatively
large thymus in proportion to the chest. And it 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 by 16 years of age,
you can hardly see the normal thymus. And so if you have a 16-year-old with a large
anterior mediastinal mass, such as the x-ray on the screen, in a child who has neurofibromatosis,
this would be highly abnormal at that age and not quite as abnormal in a two-month-old. So let’s start with a systematic approach
to the chest x-ray. We will look at the lung parenchyma, the pulmonary vasculature, the
airway and mediastinum, the heart, and the bony abnormalities as well. Lung parenchyma and vasculature. Let’s start with the lungs. The factors that
affect lung density are primarily pulmonary inflation, the pulmonary vascularity, the
lung parenchyma itself, and then overlying pleural air or fluid. Here is a 14-month-old
who presents with cough and wheezing. And the initial frontal chest x-ray shows diffuse
hazy opacification of both lungs that may mimic an overwhelming pneumonia. But you’ll notice that there are only seven
posterior ribs of inflation. A radiograph obtained two minutes later shows a marked
improvement in the opacification of both lungs. And so you can see that pulmonary hypoinflation
can markedly change how the lungs look, especially in a younger baby. Here a two-year-old who presents with new
onset stridor. We can see an asymmetry in the density of the lungs, with the left hemithorax
actually looking much more lucent than the right side. And if you notice also, 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 in the left bronchus with air
trapping and overinflation of the left lung and associated decreased pulmonary vascularity.
So asymmetry is an important thing to look for in the pediatric lung. Here are two other conditions, two other situations
where the hemithorax can look much more lucent. Both of these infants have a pneumothorax.
The infant on the left side of the screen has a medial and anterior pneumothorax. And
the infant on the right side of the screen has primarily a medial pneumothorax. Unlike
adults, where the 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 supine position.
And the lungs are relatively stiff, allowing them only to fall backwards, rather than recoil
to the center in towards the mediastinum. Now focal parenchymal abnormalities are also
very important in pediatrics. This seven-year-old presenting with cough and fever has a retrocardiac
density that is also seen overlying the spine. This is a round pneumonia, which is a bacterial
pneumonia that happens almost exclusively in children less than five years of age where
the pneumonia is mass-like in appearance because of poor development of the collateral air
passages. And so the pneumonia can look very much like a mass unlike that in adults. Here another child who presents with cough
and fever and has a right sided pneumonia. We can see that the 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 in the medial aspect of the right hemithorax. And pleural fluid is accounting
for the density lateral to the chest. And on the lateral film, we can only see one hemidiaphragm,
suggesting that this child has a pleural effusion in addition to the pneumonia. Airway and Mediastinum. Now let’s consider the airway. We need to
look at its position, its caliber, and the possibility of displacement of the airway
by abnormal structures. It’s very important to know that the airway in a young child and
infant is very mobile, and during expiration, the trachea can buckle almost to 90 degrees,
as you can see on the frontal and on the lateral view in a normal expiratory radiograph. The
other two features to consider in the trachea are that one should see the tracheal air column
on the frontal view from the thoracic inlet all the way to the bifurcation of the trachea.
And on the lateral, the course of the trachea should be a nice gentle posterior curve that
mimics the vertebral bodies of the thorax. Here is a child where these features are not
present. This two-year-old presents with new onset wheezing, and immediately we see that
the mediastinum is much too wide for a two-year-old. If you remember the first images that we showed,
the thymus in a normal child at this age should be much, much smaller. So this is a wide mediastinum
that is abnormal. The second feature is that we cannot see the
air column of the trachea on the frontal film all the way to the bronchi. We lose it in
the mid portion of the chest. On the lateral view, we can see that the trachea not only
is markedly narrowed at the thoracic inlet, but it is also anteriorly displaced by a posterior
structure. So in this situation, we have to think about things that live normally behind
the trachea. And these would be the esophagus, and/or lymph nodes. So because this happened so acutely, we can–
we’re concerned about an ingested foreign body with an abscess. Well, so we did an upper
GI and barium swallow showing that this child had ingested a sharp, plastic foreign body
that had caused perforation of the esophagus, and a periesophageal abscess that was anteriorly
displacing and compressing the trachea. So foreign bodies are an absolute must to consider
in the appropriate age group between, oh, 6 months to about 2, 2 1/2 years of age. Here’s another child that presents with an
airway abnormality. You can see that the trachea, rather than being slightly to the right of
midline, it is to the left of 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
mild narrowing of the trachea. This situation can be associated with asymptomatic
right aortic arch and a vascular ring. A CT scan in this child shows the normal caliber
trachea in the upper image and 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’ve seen before, the thymus can vary dramatically in size with age, and adenopathy
in children is much more commonly caused by inflammatory or infectious causes than in
adults. Here, we have a two-month-old who presents with cough, and has a large anterior
mediastinal mass. But if we look at it more carefully on the frontal film, we can see
through the mass on the right side, being able to see normal pulmonary markings behind
it. And on the lateral film, we can see a normal
trachea with a normal caliber and filling in of the retrosternal airspace. On closer
inspection of the left chest, we can see a scalloped appearance of this anterior medialstinal
mass, and the scalloping occurs every time an anterior rib crosses it. And this is very
characteristic of a normal thymus, which is very fatty and gets displaced by normal structures. Now, these next four images that I will show
are all children that present with the right upper lobe opacity, and we will go through
the differences between a normal structure and those that are pathologic. The image on
the left side of the screen, we’ve seen before and is a normal thymus. The features of it
are that we can see a nice, sharp inferior border, with no atelectasis of the lung inferior
to it or behind it. We can see through it, and see normal pulmonary structures behind
it. And if you notice the trachea, it is not displaced or compressed by this normal thymus. 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 border, and we cannot see any lung markings behind it. And the trachea is
slightly displaced towards this child. This is a child with pneumonia, and on occasion,
we will be able to see air bronchograms in the very dense area of a pacified lung. This second pair, we have a right upper lobe
density in 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 trachea being displaced towards this
lesion. This is right upper lobe atelectasis. And the final 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. So I’ve shown four different right upper lobe
lesions that have different characteristics that can help us distinguish from the other. Heart. Now let’s look at the heart. We often
talk about a normal cardiothymic silhouette in children rather than a cardiac silhouette
because the thymus can be so large that it will encompass the heart and go all the way
down to the diaphragms. So the shadow of the heart, 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 chest. And finally, we have a normal double atrial shadow is a normal
finding rather than an abnormal finding in adults. Here we have a five-year-old girl who presents
with cough and has a prominent left atrial shadow, shown by the arrows. This is a totally
normal finding in comparison to adults, where the prominence of the left atrial shadow can
be a pathologic finding. Bony Abnormalities. Finally, a look at the skeletal system is
very important when looking at a chest x-ray, especially if we’re looking at fractures for
erosions and absence of normal bony structures. Here, we have a nine-month-old who fell from
her bed. And initially the heart looks normal. The trachea and mediastinum are normal. And
yet, when we look at the left sided ribs, we can see that there are multiple posterolateral
rib fractures as shown by the arrows. Posterior and lateral rib fractures in infants below
six months of age are very concerning for non-accidental trauma. So these are very important
findings to make on the chest x-ray and often require oblique images for better evaluation. Here, another child who presents at two years
of age with irritability. We see what appears to be initially a normal chest x-ray. But
if we pay more attention to the right 11th rib, we see that the rib density is a modeled
and 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. So 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, the pulmonary vasculature,
the airway and mediastinum, the heart, and bony abnormalities. These are some final take
home points that I would like to leave you with. First, look at the symmetry of the lungs
for density and for pulmonary vascularity. Second, make sure you look at the lung behind
the heart because it’s a favorite place for pneumonias to hide. Make sure you look at
the size in the position of the trachea, the bones, and soft tissues. And finally, ask for help if you have any
concerns at all. Thank you. Please help us improve the content by providing
us with some feedback.


7 thoughts on ““Introduction to Pediatric Chest Radiography” by George Taylor for OPENPediatrics

  1. Very good systematic approach with very clear and simple explanatient, really I love it , God bless you. Many thanks

  2. Excellent lecture sir. plz we want to learn more by you. your way of teaching is Mashallah excellent. May Allah SWT bless you always. Ameen

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