Hemithorax Opacification

00:01 So what happens when you see a completely opacified hemithorax? What could be the cause? In this lecture, we're going to go over several cases that will help you identify the cause of the opacification.

00:11 Let's start off with this case.

00:14 So we have an entirely opacified left hemithorax.

00:17 That just means that the entire left hemithorax appears white.

00:20 We don't see any air within it.

00:22 So what is your differential diagnosis? It could be complete atelectasis, this could represent a large pleural effusion, this could be diffuse consolidation, or this could be a pneumonectomy.

00:36 Those are really the four major causes.

00:38 The fifth is that it could be a mixed pattern.

00:41 So let's see how we can help differentiate between each of these causes.

00:45 So let's take a look at this case.

00:49 Here we have an opacified right hemithorax.

00:52 So what do you see here? Is there anything here that can help you decide which of those causes this could be a result of? So this is actually a very large pleural effusion.

01:08 The arrow points out a meniscus and that helps you to determine that this is a large pleural effusion.

01:13 So this is a large amount of fluid that fills the pleural space then it compresses the adjacent lung.

01:20 You have shift of the mediastinal structures away from the side of opacification.

01:24 So let's take a look at this diagram that's here.

01:27 You can see normal lung here.

01:30 The lung is surrounded by a visceral pleura and then just outside of the visceral pleura is the parietal pleura.

01:38 In between the two which is the pleural space is where this fluid accumulates.

01:41 If the hemithorax is not completely opacified, you may see a very small meniscus of fluid just like we saw superiorly in this patient.

01:53 This here is an example of a lateral view which shows what a meniscus would look like.

01:57 So you see here blunting of the angles and you see a blunting of the angle anteriorly as well.

02:04 So this is a common finding of a meniscus.

02:06 So the differential diagnosis when you see a massive pleural effusion like this, is malignancy, tuberculosis, possibly trauma, which means that the fluid is blood or a hemothorax, or liver disease.

02:19 Less common is CHF or congestive heart failure because that usually causes bilateral pleural effusions.

02:25 Let's take a look at this case.

02:28 So again, we have a complete opacification of the left hemithorax.

02:33 Are there any other clues here that help you decide what's causing this? This is an example of a CT scan of the same patient.

02:44 This is the coronal view.

02:45 We have post-contrast images and let me just help you identify.

02:48 This right here is the heart and this is the normal right lung.

02:52 So let's just scroll through this.

02:55 So what do you think this represents? This is actually an example of complete atelectasis.

03:11 So this is complete obstruction of the bronchus which results in no air entering that lung and you have complete collapse of that lung.

03:18 So the visceral and the parietal pleura actually remain attached which results in a shift of all the mediastinal structures towards the side of the atelectasis.

03:27 So again, keep in mind, with the massive pleural effusion, you have mass effect and the mediastinal structures shift away from the side of the opacification while with atelectasis, you have loss of volume and all of the mediastinal structures shift towards the side of the atelectasis.

03:42 You can see here one way of knowing that the atelectasis, the mediastinal structures have shifted towards the atelectasis is looking at this trachea.

03:50 So you can see that the trachea is deviated towards the side of the opacification which indicates that there is loss of volume on that side.

03:58 Common differentials here would include neoplasm or mucous plugs.

04:04 Anything that can result in complete obstruction of the bronchus.

04:08 Mucous plugs are commonly seen in diseases such as asthma or cystic fibrosis.

04:12 So let's take a look at this case now. We have complete opacification of the left hemithorax.

04:21 The trachea actually looks like it's still in midline.

04:25 So what could this be? This is an example of pneumonia or opacification of the alveoli with exudate.

04:39 There's no shift of mediastinal structures and this is common with pneumonia.

04:43 It doesn't really cause mass effect and it also doesn't cause loss of volume.

04:47 So the midline stays in the midline.

04:50 You have no shift of the trachea and you may have air bronchograms.

04:54 In this patient, we actually don't see any air bronchograms but occasionally, you may see that and that can help you with the diagnosis.

05:00 So here's another case.

05:04 So we have opacificaton of the right hemithorax and we have shift of the trachea towards the right.

05:10 So what do you think this could be? This is actually a pneumonectomy.

05:22 So what you wanna look for are surgical changes such as resection of the 5th/6th ribs or possibly surgical clips.

05:28 The opacification of the hemithorax takes a few weeks to develop after a surgery.

05:34 So when you see this, the two things that you would think about are atelectasis or pneumonectomy. Both result in loss of volume and both result in shift of the structures towards the side of the opacification.

05:44 However, when you see post-surgical changes that will help you determine that this is actually the result of a pneumonectomy.

05:51 The space actually fills with fluid and fibrotic tissue and as you see here, the mediastinum shifts towards the side of the pneumonectomy.

06:01 So you can also have a mixed pattern.

06:05 You can have a mix of fluid and atelectasis and because of this, you would have no shift of mediastinal structures because one would counteract the other.

06:12 So in this case, it can be a little bit more difficult to determine exactly what's going on.

06:17 A CT would help you.

06:19 So let's just review again.

06:22 So with atelectasis, you have shift of the mediastinal structures towards the side of the atelectasis or towards the side of the opacification.

06:29 You really don't have any other findings that can help you.

06:32 With the pleural effusion, you have shift away from the pleural effusion because the effusion causes mass effect.

06:38 In effusion, you may see a meniscus if the entire hemithorax is not fully opacified.

06:43 Pneumonia, you have no shift of mediastinal structures but you may have air bronchograms that can help you and with pneumonectomy, just as in atelectasis, you again have shift towards the side of the pneumonectomy but you will see surgical changes such as a rib resection or surgical clips.

06:59 With a mixed pattern, the shift is uncertain.

07:03 It depends on how much of an effusion or how much of a pneumonia you have versus how much of an atelectasis you have.

07:08 There really are no other findings and the best way to determine what's going on is to do a CT of the chest.