Lateral Chest X-Ray Reading Guide

Hey everybody, it's Rishi Agarwal, and in this video I'm going to show you how I look at a lateral chest x-ray. Now this is not going to be an exhaustive list of the anatomy because I want to save that for another longer video, but I'm going to cover the basics here. Most of the time the abnormalities you'll see on chest x-ray will be on the frontal view, and you'll use the lateral view to localize lesions. But sometimes there's lesions that are more obvious on the lateral view, and occasionally... You'll even have lesions that you can only see on the lateral view and not on the frontal view at all. So when I open up a lateral chest x-ray, the first thing that I look at is this area right here. And this is where the right and left hyla are superimposed over each other. And there's an important landmark in this area, and that is this lucency centrally right here. And that's the left upper lobe bronchus. And the reason why that's important is because it serves as a landmark for other anatomic structures. So just anterior to the left upper lobe bronchus is this structure right here. And it's kind of a rounded structure. And that is the right pulmonary artery. And then kind of arching over, The left upper lobe bronchus is another vessel, and you might guess what that is. So we have the right over here, this is the left pulmonary artery. Okay, so if you imagine this as a clock face, then the right pulmonary artery takes up the nine o'clock position, and the left pulmonary artery goes from like 10 o'clock to about three o'clock. And inferior, to the left upper lobe bronchus, you have this sort of lucent area. And that is normal, and that is called the infrahylar window. Infrahylar window. And if you see opacity in that area, then usually what you're looking at is hylar-or mediastinal lymphadenopathy. Okay, so normally that area is lucent. Okay. So the next thing that I look at after I've looked at the hyla are the clear spaces. And there's three clear spaces on the lateral radiograph. The first one that I look at is right here, and it is just behind the sternum. So this is appropriately named the retro-sternal clear space. And... If I see abnormality in that area, it could mean that there's airspace disease in one of the upper lobes, or it could also mean that there's an anterior mediastinal mass. The next place I look is behind the trachea. So the trachea is this lucent structure right here. And just behind that is another clear space, and it's bordered posteriorly by the spine, inferiorly by the aortic arch. and anteriorly by the trachea. And so this is called the retrotracheal clear space or retrotracheal triangle, or it's also called Rader's triangle. You might hear that term. And usually in that area, it's vascular anomalies like an aberrant right subclavian artery can show up in this area, and you can have other vascular anomalies here. Or you can see abnormalities with the esophagus, because the esophagus lies just posterior to the trachea. Okay, and then the third clear space is down here, and is just behind the heart, and the superior border of it is a little bit ill-defined, so I'm just going to draw that as like a dotted line. And this is called the retrocardiac, retrocardiac clear space. And... In that area, commonly you'll see lower lobe consolidation or you might see masses. And this is also where you'll see a hiatal hernia. So those are the three clear spaces of the lateral chest x-ray. After I've looked at the clear spaces, the next thing I do is I look at the heart. So on the lateral view, the right ventricle sits right here. Okay, this is the right ventricle. And in this patient, notice that the right ventricle only comes up to approximately like a third of the way up the sternum. Okay, so in other words, like this is the whole sternum and manubrium here, and this is like two-thirds of the manubrium and sternum are here, whereas the rest down here is a... approximately 1 3rd, and that's normal. When the right ventricle starts to encroach upon the retrosternal clear space and go this way, then that's a sign of right ventricular hypertrophy. So that's right ventricle, and then we have the left ventricle back here. This is the posterior border of the left ventricle. And in a patient with left ventricular hypertrophy, The retrocardiac clear space becomes much smaller because the left ventricle moves out in that direction. The main pulmonary artery and the ascending aorta are not really things that you can evaluate well on the lateral view, and that's because they're partially superimposed over each other. Occasionally, residents will try to measure the aorta by going from here to here, but you can't really do that because some of this opacity is the pulmonary artery and some of it is the aorta. It is common to see aortic enlargement if it involves the distal part of the arch, which is here, or the descending aorta, which is about right here. A lot of times in older patients, the descending aorta is tortuous, and that shows up on the lateral view. And then sometimes you can see aneurysms of the descending aorta on the lateral view too. The next thing I look at are the bones, and mainly on the lateral view, I'm looking at the spine. And the spine and the vertebral bodies show up really well on the lateral view. So I'm looking back here, making sure that there's no vertebral compression deformities. And I'm looking at the sternum anteriorly here because a sternal fracture is virtually impossible to see on the frontal view. The lateral view isn't really good for looking for rib fractures, although occasionally you do see them. And then... And occasionally you also see fractures of the scapula. So here's one of the scapula right here, and then the other scapula is right here. After I'm done looking at the bones, the next thing that I do is I look at the diaphragm. So the diaphragm is of course right here. I have another video with a few different ways on how to tell the right from the left side of the diaphragm. So I'm not going to go over that here. But while I'm looking at the diaphragm, I'm looking at the costophrenic angles, which are back here posteriorly. And remember that if you have blunting of the posterior costophrenic angles, that's a sign of pleural effusion. Also remember that the lateral view is much more sensitive for detection of small amounts of pleural fluid compared to the frontal view. And then finally, after I'm done looking at the diaphragm, I look below the diaphragm to see if I can see abnormalities in the upper abdomen. Alright, so that's been a quick overview of how I look at a lateral chest x-ray. If you have any questions about this topic or any other chest topic, let me know in the comments below. Thanks.

You'll even have lesions that you can only see on the lateral view and not on the frontal view at all. So when I open up a lateral chest x-ray, the first thing that I look at is this area right here. And this is where the right and left hyla are superimposed over each other. And there's an important landmark in this area, and that is this lucency centrally right here. And that's the left upper lobe bronchus.

And the reason why that's important is because it serves as a landmark for other anatomic structures. So just anterior to the left upper lobe bronchus is this structure right here. And it's kind of a rounded structure. And that is the right pulmonary artery.

And then kind of arching over, The left upper lobe bronchus is another vessel, and you might guess what that is. So we have the right over here, this is the left pulmonary artery. Okay, so if you imagine this as a clock face, then the right pulmonary artery takes up the nine o'clock position, and the left pulmonary artery goes from like 10 o'clock to about three o'clock.

And inferior, to the left upper lobe bronchus, you have this sort of lucent area. And that is normal, and that is called the infrahylar window. Infrahylar window. And if you see opacity in that area, then usually what you're looking at is hylar-or mediastinal lymphadenopathy.

Okay, so normally that area is lucent. Okay. So the next thing that I look at after I've looked at the hyla are the clear spaces.

And there's three clear spaces on the lateral radiograph. The first one that I look at is right here, and it is just behind the sternum. So this is appropriately named the retro-sternal clear space. And...

If I see abnormality in that area, it could mean that there's airspace disease in one of the upper lobes, or it could also mean that there's an anterior mediastinal mass. The next place I look is behind the trachea. So the trachea is this lucent structure right here.

And just behind that is another clear space, and it's bordered posteriorly by the spine, inferiorly by the aortic arch. and anteriorly by the trachea. And so this is called the retrotracheal clear space or retrotracheal triangle, or it's also called Rader's triangle.

You might hear that term. And usually in that area, it's vascular anomalies like an aberrant right subclavian artery can show up in this area, and you can have other vascular anomalies here. Or you can see abnormalities with the esophagus, because the esophagus lies just posterior to the trachea.

Okay, and then the third clear space is down here, and is just behind the heart, and the superior border of it is a little bit ill-defined, so I'm just going to draw that as like a dotted line. And this is called the retrocardiac, retrocardiac clear space. And...

In that area, commonly you'll see lower lobe consolidation or you might see masses. And this is also where you'll see a hiatal hernia. So those are the three clear spaces of the lateral chest x-ray.

After I've looked at the clear spaces, the next thing I do is I look at the heart. So on the lateral view, the right ventricle sits right here. Okay, this is the right ventricle. And in this patient, notice that the right ventricle only comes up to approximately like a third of the way up the sternum.

Okay, so in other words, like this is the whole sternum and manubrium here, and this is like two-thirds of the manubrium and sternum are here, whereas the rest down here is a... approximately 1 3rd, and that's normal. When the right ventricle starts to encroach upon the retrosternal clear space and go this way, then that's a sign of right ventricular hypertrophy.

So that's right ventricle, and then we have the left ventricle back here. This is the posterior border of the left ventricle. And in a patient with left ventricular hypertrophy, The retrocardiac clear space becomes much smaller because the left ventricle moves out in that direction. The main pulmonary artery and the ascending aorta are not really things that you can evaluate well on the lateral view, and that's because they're partially superimposed over each other. Occasionally, residents will try to measure the aorta by going from here to here, but you can't really do that because some of this opacity is the pulmonary artery and some of it is the aorta.

It is common to see aortic enlargement if it involves the distal part of the arch, which is here, or the descending aorta, which is about right here. A lot of times in older patients, the descending aorta is tortuous, and that shows up on the lateral view. And then sometimes you can see aneurysms of the descending aorta on the lateral view too. The next thing I look at are the bones, and mainly on the lateral view, I'm looking at the spine. And the spine and the vertebral bodies show up really well on the lateral view.

So I'm looking back here, making sure that there's no vertebral compression deformities. And I'm looking at the sternum anteriorly here because a sternal fracture is virtually impossible to see on the frontal view. The lateral view isn't really good for looking for rib fractures, although occasionally you do see them. And then... And occasionally you also see fractures of the scapula.

So here's one of the scapula right here, and then the other scapula is right here. After I'm done looking at the bones, the next thing that I do is I look at the diaphragm. So the diaphragm is of course right here.

I have another video with a few different ways on how to tell the right from the left side of the diaphragm. So I'm not going to go over that here. But while I'm looking at the diaphragm, I'm looking at the costophrenic angles, which are back here posteriorly.

And remember that if you have blunting of the posterior costophrenic angles, that's a sign of pleural effusion. Also remember that the lateral view is much more sensitive for detection of small amounts of pleural fluid compared to the frontal view. And then finally, after I'm done looking at the diaphragm, I look below the diaphragm to see if I can see abnormalities in the upper abdomen.

Alright, so that's been a quick overview of how I look at a lateral chest x-ray. If you have any questions about this topic or any other chest topic, let me know in the comments below. Thanks.

Transcript for:Lateral Chest X-Ray Reading Guide

Transcript for:
Lateral Chest X-Ray Reading Guide