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Hi everyone, this is Mark again, and

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we're going to keep going in the Mastery

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Series, and we're going to talk about

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one of my favorite topics, ground glass.

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Not a topic many radiologists like, but

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I hope you're going to appreciate the

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approach, and this will help you when you

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encounter this very common imaging pattern.

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We're going to start off by looking at

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ground glass from the adage of acute.

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So acute means usually less than,

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you know, a week of symptoms.

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We'll review some of the common

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differentials for these patients, and

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we'll emphasize the importance of pleural

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effusion versus no pleural effusion.

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When you're looking at someone with an acute

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ground glass process, and also talk a little bit

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about how, uh, distribution can be very helpful.

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Again, these sessions are to

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expose an old propagated myth.

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As false, ground glass is

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just long differentials.

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That's not true at all.

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It's how we organize.

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It's so important. So just a quick review,

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ground glass, when you have a normal lung,

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you can see the pulmonary vessels, the veins

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and the arteries very well. They're sharply

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defined. That tells you there's a pulsed

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amount of air around, um, the vessels.

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When a ground-glass process starts to

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develop, there's an increasing area of

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opacification and causes the vessels

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to become more difficult to see.

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You still see them as opposed to

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consolidation, but they're more difficult.

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They're fuzzy.

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Uh, almost like the old fifties,

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frosted pane, shower door glass.

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You know, someone walks in, you

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can see there's someone there.

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You just don't know who it is.

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All right, ground glass can be used

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for both radiographs and CTs and

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the differentials more similar.

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Um, obviously the CT will

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pick it up more easily, right?

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You know, it's, it's more sensitive to picking

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it up and subtle ground glass usually see

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when you see that dark bronchus sign, right?

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The bronchi and the parenchyma

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shouldn't be the same density.

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So, what is your differential with

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an acute ground-glass process?

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Well, it's pretty straightforward.

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It's the same, essentially,

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as acute consolidation.

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It's blood, pus, or water.

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Now, what order you put them in can be very

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helpful to see if there's pleural effusion.

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If there are small pleural effusions, we call

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that the wet diseases, and that's usually

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hydrostatic edema or non-cardiogenic edema.

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Now, if there's absolutely no pleural fluid

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at all, I kind of, we refer to that as the

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dry disease and things like Pneumocystis

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and pulmonary hemorrhage syndrome, acute

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hypersensitivity pneumonitis, and acute

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lung injuries such as diffuse alveolar damage.

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Those don't tend to have pleural effusions.

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So you switch your order on your differential.

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Okay.

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This, uh, pleural effusion observation came

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from a colleague of mine, uh, Greg Johnson, Dr.

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Greg Johnson.

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So two patients with acute

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ground-glass opacities.

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And you can see here, they're

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both relatively extensive.

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This one has no pleural effusion,

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and this one has ground glass and

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septal lines and bilateral effusion.

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So you would say, Hey, this is more

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likely hydrostatic pulmonary edema,

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especially with the septal lines.

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And in fact, I wouldn't give a differential.

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That's the diagnosis.

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The other one you'd say, well, could

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that be congestive heart failure?

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No, unlikely, right?

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No pleural fluid.

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So you think of the dry disease, and this

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turned out to be an acute lung injury

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from, um, in this case, CMV pneumonitis.

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Another patient, just take a look,

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and here's, here's your choices.

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You got a 40-year-old with dyspnea

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over two days, so it's acute.

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Um, what would you most likely report

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as the pathologic process, right?

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We got a lot of ground glass, there is no

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pleural effusion, there's a little bit of

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subpleural sparing, and these little holes are

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areas of emphysema because nothing gets in.

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Emphysema when it forms, right?

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Nothing gets in, nothing gets out.

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It's like a balloon.

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So is it hydrostatic edema,

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pulmonary hemorrhage, non-cardiogenic

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edema, or alveolar prognosis?

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Well, you know, in this case,

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it's pretty straightforward.

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It's most likely going to be

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pulmonary hemorrhage syndrome.

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Is it common?

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No, but this is very

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commonly what it looks like.

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There's no effusion.

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It's not hydrostatic edema because there's no

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pleural fluid and it's not alveolar prognosis

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because that's more of a chronic process.

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If you said non-cardiogenic edema as your

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second choice, I think it's reasonable with

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an acute lung injury kind of thing to say,

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but you'd probably favor pulmonary hemorrhage

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syndrome first, which is what it was, by the

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way, ground glass again, you can use it on

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radiographs, there'll be that hazy increased

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capacity, but distribution is very helpful.

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In this person, they have ground glass,

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they have no pleural fluid, but they have a

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very much of an upper lobe distribution.

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And in that case, you can come down pretty

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hard and say, hey, you know, these findings are

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most consistent with a pneumocystis pneumonia.

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You know, especially if the patient

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has been tapered for steroids or has

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HIV and is hypoxic, which they were.

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Another patient with upper lobe, again,

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pneumocystis, ground glass, usually

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acute symptoms, usually within a week.

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Uh, hypoxia definitely has a

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sort of perihilar and upper lobe

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distribution, which can be very helpful.

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No pleural fluid.

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Another patient.

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This one's a little different.

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Acute onset, shortness of

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breath, lots of ground glass.

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In fact, there might even be some early

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consolidation forming here where the

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vessels are getting more difficult to see.

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They also have a very large

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pneumomediastinum, right?

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Because you can see the, um, the

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continuous diaphragm sign here, um,

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the gas extending up into the neck.

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This is very characteristic of someone

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who's got acute onset, shortness of

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breath and altered lung compliance.

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They start coughing and they rupture some of the

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alveoli and the gas then goes into the mediastinum

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and up in the neck and into the retroperitoneum.

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The key here is the distribution.

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It's diffuse and diffuse is a very helpful

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finding in the setting of acute ground glass.

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Because that kind of tells us that the

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etiology of this lung injury is coming

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from the outside of the lungs, not within.

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So you think of systemic causes.

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And in that acute setting, you'd say,

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well, you know, that's consistent with

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non cardiogenic edema or developing

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ARDS, potentially from sepsis,

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pancreatitis, transfusion reaction, right?

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Things from outside.

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And then pulmonary hemorrhage syndromes,

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because if it's hemorrhage, and it's that

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diffuse, you start going along the anti-

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glomerular, uh, anti-basement membrane, um,

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kind of things, uh, hypersensitivity, pulmonary

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hemorrhage syndromes, these sort of things.

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So it's, when it's uniform,

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but it's got to be uniform.

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Now, if it's not, you say it's extensive,

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but when it is uniform and diffuse, you

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say it's diffuse, and that implies the

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etiology is coming from outside the lung.

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Post C-section, acute onset, shortness

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of breath in this young lady.

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Diffuse ground glass, some consolidation.

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Remember the two can coexist.

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Um, you know, clinician said,

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"Oh, this is a pulmonary embolus."

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No, it's not.

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No, right?

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It's, it's an acute lung injury.

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Non-cardiogenic edema and etiology

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had to have occurred outside.

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This occurred shortly after

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they had a transfusion.

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So this was a transfusion-

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related non-cardiogenic edema.

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Patchy areas of ground glass with

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fever, no pleural fluid here.

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Well, you'd say, "Well, don't use

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the word nonspecific, right?"

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Earn your paycheck.

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It's patchy bilateral areas of ground

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glass, no pleural effusion, acute symptoms.

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Oh my gosh, they have a fever.

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This turned out to be COVID-

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related acute lung injury.

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Very characteristic appearance.

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Um, there are some other things that can, other

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infections that can do that too on occasion, but

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you know, currently COVID would be the big one.

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Alright, so the summary, ground glass, it's

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a common manifestation of a lot of different

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acute pathologies, but really when you get

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down to it, it's kind of blood plus water,

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and the presence or absence of pleural fluid

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can be very helpful in how you determine

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or prioritize which one

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you think is most likely.

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Um, remember dry lungs, pulmonary hemorrhage

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syndrome, pneumocystis, acute lung injury,

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very common if there's no pleural fluid.

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Distribution can also be helpful,

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especially if it is diffuse.

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That tells you it's a systemic etiology.

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All right.

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I hope you found that one helpful.