0:01

Hi, it's Mark again.

0:02

Uh, this segment we're going to build upon

0:05

our acute consolidation, but we're going

0:07

to focus a little bit more on infarcts.

0:10

And that is a form of consolidation,

0:13

but it looks distinctly different than

0:16

the previous examples of consolidative

0:18

pneumonia or pulmonary hemorrhage.

0:21

So the imaging appearance of

0:22

consolidation usually has a bronchogram.

0:25

Okay.

0:26

When there are no air bronchograms present,

0:28

that's when we start thinking, well, it

0:31

still could be a consolidated pneumonia, but

0:33

maybe there's necrosis, maybe it's obstructed

0:35

and it's a drowned lung where there's

0:37

filling of the airways, or maybe this is

0:40

an infarct, a pulmonary infarct.

0:43

Um, I'm going to highlight that

0:46

the dual blood supply to the lungs.

0:48

Infarcts are actually not that common in

0:51

the lung, and that's because the lung is

0:53

kept alive with the bronchial arteries.

0:55

And then we'll review the differences

0:56

of enhancement of a consolidation versus

0:59

an infarct/necrotizing pneumonia.

1:03

So acute consolidation, uh, again, less

1:07

than a week is defined as ill-defined,

1:09

a pacification completely obscuring the

1:10

vessels, no reason to say airspace or

1:13

interstitial, and please don't say infiltrate.

1:16

What we talked about in the first

1:18

three, so now we're going to look at

1:19

the last one, the pulmonary infarct.

1:22

Um, usually these look different, and here

1:26

is your differential, uh, things like,

1:28

uh, Wagner's granuloma, which now we call

1:31

anchor-related granulomatous vasculitis, uh,

1:33

pulmonary embolus, angioinvasive aspergillus.

1:36

You could also put mucormycosis

1:38

in there, and recreational drugs

1:40

like cocaine can induce it too.

1:43

Now, infarcts, they don't have air bronchograms.

1:47

Okay, that's a key component, and

1:50

they're not common because the lung is

1:53

kept alive with the bronchial arteries.

1:54

You can occlude the pulmonary

1:56

artery, and there will be no infarct.

2:00

Um, the farther out, like emboli go, when

2:03

they're in the tiny pulmonary arteries, they're

2:05

more likely to actually give you an infarct.

2:08

And I'm not sure if it's just because the flow

2:10

from the bronchial arteries or collateral flow

2:12

is not quite the same, but that is also why.

2:15

The lung develops what's called a red infarct;

2:18

you might remember that from medical school.

2:19

Most parts of the body, when they

2:21

infarct, it's a white infarct.

2:23

But the lung, like the liver and

2:26

the intestine, um, they get red

2:28

infarcts because they're hemorrhagic.

2:31

Remember now, the lung is a filter.

2:33

That's really what its other purpose is.

2:35

It filters out tumor.

2:37

That's why metastases are so common there.

2:40

It filters out bacteria, and that's why you

2:43

can get septic emboli, and it also filters

2:46

out the emboli, which is a good thing, right?

2:48

Because the pulmonary arteries will

2:49

catch it, and they'll break it down.

2:50

It's better than that than going to

2:52

the brain, where it's the brain,

2:54

or the body, or you know, the heart.

2:56

It really doesn't react

2:57

well to even small emboli.

3:00

Now, what does an infarct

3:01

versus consolidation look like?

3:02

Well, this is an infarct.

3:04

Notice it is actually a consolidation,

3:06

but there are no air bronchograms.

3:08

It may have some surrounding ground glass.

3:10

Consolidation usually has air bronchograms.

3:13

Histologically, they look different.

3:16

The airways tend to be open here, but

3:18

in an infarct, everything kind of dies.

3:21

And so there's blood that fills the parenchyma.

3:24

There's blood that fills the bronchi,

3:26

and everything is just sort of opacified.

3:30

This is a BMT patient.

3:31

They have a pulmonary infarct.

3:33

This is, it can be nodular.

3:35

It could be, you know, wedge-shaped,

3:37

I guess, or the Hampton's Hump.

3:38

It's not usually wedge.

3:40

And, or it just can be an area of

3:42

consolidation that has no air bronchograms.

3:45

You may see some bronchograms on the

3:48

periphery, but not usually centrally.

3:51

Okay, this has surrounding ground-glass.

3:53

This was in, um, a fungal infection.

3:55

Mucormycosis, um, angioinvasive

3:58

aspergillus, though, is more common

4:00

and it looks exactly the same.

4:02

You can't tell the difference

4:03

between the two on imaging.

4:04

And what it represents is the aspergillus

4:07

invades the pulmonary and bronchial arteries.

4:10

So both arteries, and they kind

4:12

of go through like stormtroopers

4:13

in there and thrombus it off.

4:15

And then since both are affected,

4:18

that lung has an infarct.

4:20

Infarcts can be small.

4:23

This is the so-called halo sign of an

4:25

infarct of surrounding hemorrhage

4:26

from angioinvasive aspergillus.

4:29

And it's in the name, right?

4:30

It's angioinvasive.

4:34

Another patient with angioinvasive

4:36

aspergillus, there's an area of

4:37

necrosis, a so-called crescent sign.

4:39

This is an area of dead lung.

4:41

In radiology literature, it's commonly

4:45

taught that aspergillus occurs in BMT

4:47

patients within the first 30 days.

4:48

That's, uh, that's untrue.

4:50

The peak incidence in two large European

4:52

studies was about 120 days out.

4:56

So aspergillus, they have a great

4:58

deal of antifungal coverage

5:01

during the first 30 to 60 days.

5:04

Aspergillus tends to manifest at a later time

5:07

than what radiology literature says.

5:10

So, is this a subacute infarct?

5:12

No, there's no surrounding ground-glass.

5:14

It's well-defined.

5:16

There is sort of a little lucency here, and

5:18

it's common with these subacute infarcts

5:21

to have a little bit of this kind of weird

5:23

misty ground-glass within it, but really

5:26

there aren't any definite air bronchograms.

5:29

This is a resolving infarct and subacute

5:32

infarcts or infarcts take a while to resolve.

5:35

They kind of melt away, the so-

5:37

called melting iceberg sign.

5:38

It can take weeks for them to go away.

5:41

If you see any cavitation within an infarct,

5:45

please assume there is an infection present.

5:48

Okay.

5:49

Some people say infarcts can cavitate.

5:53

This is how infarcts go away.

5:54

Cavitation usually indicates

5:56

there is an infection.

5:58

Also present is a 42-year-old HIV patient with a large area of

6:02

consolidation, but notice the air bronchograms

6:05

are only at the periphery, but not here.

6:07

Hmm.

6:08

That's not good.

6:10

Well, it turns out it's because this

6:12

person has necrotizing pneumonia.

6:15

So in necrotizing pneumonia,

6:18

that's essentially the same as

6:19

an infarct in some ways, right?

6:21

Everything dies.

6:22

And the bronchi die, they fill up,

6:25

they necrose, they fill up with

6:27

fluid, and there are no air bronchograms.

6:29

So your differential of an infarct

6:32

is necrotizing pneumonia.

6:35

And this is the other differential.

6:37

It is a drowned lung.

6:39

The radiologist read this as

6:40

pneumonia with a pulmonary embolus.

6:43

Well, let's take a look at that.

6:45

First of all, there's no air bronchogram.

6:47

So when you don't see that,

6:48

you want to pause for a moment.

6:50

Why are there no air bronchograms?

6:52

The second thing is, you

6:54

notice the fissure is convex.

6:56

Well, that's the Golden's sign, right?

6:58

That tells us the fissure is

7:00

sitting on some sort of mass.

7:02

And this mass likely is

7:03

obstructing the right middle lobe.

7:06

And the obstruction, all the

7:07

secretions build up and can't get out.

7:09

So that's a drowned lung.

7:12

The other thing that they called an embolus

7:14

was actually a mucus plug in the bronchi.

7:18

So, but this turned out to be

7:21

a right middle lobe mass, drowned

7:22

lung, post-obstructive pneumonia,

7:24

and a mucus plug.

7:26

Ready?

7:26

Man, chest is hard, man.

7:28

Chest is hard.

7:30

Enhancement pattern.

7:31

Pneumonias.

7:32

Consolidation.

7:33

It enhances the same as the paraspinal muscle.

7:36

Atelectasis enhances greater.

7:39

We went through that.

7:41

This is enhancement of a, basically, a

7:44

drowned lung without air bronchograms, but

7:46

there is no evidence of necrosis here.

7:48

The enhancement pattern

7:49

is the same as the muscle.

7:51

This is the enhancement

7:52

of an infarct.

7:55

It doesn't.

7:56

There is no enhancement.

7:57

It is less dense than the paraspinal.

7:59

So if you see an area of consolidation

8:01

that doesn't, on a CT with contrast, that

8:03

doesn't enhance to the same degree as the

8:05

paraspinal, that's highly suspect to represent

8:09

an infarct or necrotizing pneumonia.

8:13

Quick question, acute pleuritic

8:14

chest pain is useful to distinguish

8:16

bacterial pneumonia from infarct, is it?

8:19

No, it is not.

8:20

An acute pneumonia will give

8:22

you acute pleuritic chest pain.

8:24

Okay.

8:25

The pneumonia is going through a rapid exudative

8:27

phase, inflames the pleura, sudden onset

8:30

pleuritic chest pain with fever and chills.

8:32

Okay, an infarct inflames the parietal

8:36

pleura as well, but it does so differently

8:40

Last one.

8:41

Here's your case: It's an 85-year-old or, sorry,

8:44

but it's an 85-year-old with fevers for five days.

8:48

There's consolidation in this

8:50

patient with BMT. CT shows these

8:54

consolidations and surrounding ground glass.

8:57

Well, this is angioinvasive aspergillus, right?

9:00

Well, what's the issue here?

9:01

Well, there are air bronchograms

9:02

present throughout all of these.

9:04

Well, that's odd.

9:05

That doesn't make sense, right?

9:08

So what is this?

9:09

I mean, is it angioinvasive aspergillus?

9:11

They are at risk.

9:13

Is it bacterial pneumonia,

9:14

multiple emboli with infarcts, or

9:16

pulmonary vasculitis with infarcts?

9:18

No, there are air bronchograms.

9:21

You would favor that this is a multifocal

9:23

consolidated process like pneumonia.

9:26

And it did turn out that the patient had a

9:28

bacterial pneumonia; it was Strep pneumonia,

9:31

and look at the radiograph after five days,

9:33

which would pretty much confirm it because

9:35

remember, infarcts take a long time to resolve.

9:38

So the presence of air bronchograms

9:40

was really quite useful

9:41

for that particular patient.

9:43

So, summary of infarcts: consolidation

9:46

without air bronchograms raises the

9:48

possibility of a drowned lung from

9:50

post-obstruction or necrotizing

9:52

pneumonia as other possibilities.

9:55

Infarcts are not that common in the

9:56

lung because of the dual blood supply.

9:59

And look at the enhancement.

10:00

If the enhancement is less than

10:02

the paraspinal muscle, that suggests

10:04

an infarct or necrotizing pneumonia.

10:08

With that, I thank you.