0:00

What's our diagnostic approach

0:03

for diffuse cystic lung disease?

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So a CT comes in, you're looking at a CT scan.

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You think to yourself, could this be a

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diffuse cystic lung disease?

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The first thing you want to do is exclude mimics.

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So central lobular emphysema

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and sometimes paraseptal emphysema can look like

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diffuse cystic lung disease.

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So you have to kind of like look carefully and

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and just kind of like make sure

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that you're not just dealing a case of that.

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Remember sometimes central lobular emphysema when you have a

0:29

superimposed infiltrative abnormality, whether it's edema,

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atypical infection, hemorrhage, aspiration,

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if you get something superimposed on that central emphysema,

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it can look super odd.

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It could look like a interstitial lung disease

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or diffuse lung disease.

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And so I will very, very seldom call any sort

0:47

of diffuse interstitial lung disease

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unless I'm 100% sure in the acute setting,

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in the inpatient or EG setting.

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'cause usually they're coming in with something acute.

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So even if they have underlying chronic disease like

0:58

emphysema or pulmonary fibrosis,

0:59

usually there's a superimposed acute process on top of it

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and that makes making an accurate diagnosis quite difficult.

1:05

So you have to be very aware of that.

1:07

So I usually will make, say

1:09

that this patient needs a follow-up three or six months

1:10

after they get discharged with an HR CT using inspiratory,

1:14

expiratory and prone imaging.

1:16

And then once that inflammation,

1:18

that acute event has passed, whether whatever it was,

1:21

whether it was infection, aspiration, edema,

1:24

whatever the heck it was, now you're left

1:26

with a more pure form of the chronic lung disease

1:28

and you can make a better determination of what's going on.

1:32

So bottom the line don't fall into that trap, right?

1:36

I've fallen into that trap before.

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So, okay, so anyways, exclude emphysema.

1:40

Next thing is you wanna make sure there are enough cysts

1:42

to start to think about diffuse cystic lung disease

1:45

and depends who you talk to.

1:48

But what is enough cysts?

1:50

So I was taught five to seven,

1:52

so I use seven cyst if there's more than seven cyst,

1:54

I think, okay, diffuse cystic lung disease.

1:56

I know other people use five, but why is this?

1:59

It's because you wanna exclude these cases

2:01

of post-infectious or post-traumatic no seals.

2:05

And so a lung though I love the lung

2:08

parenchyma is only so smart.

2:09

That's just the truth of it, right?

2:10

So the lungs can only react

2:13

to adverse stimuli in a handful of ways.

2:16

And so sometimes when it gets infected it heals

2:18

or it gets, it gets dinged from trauma and it heals.

2:21

It heals as a pneumatic seal, which just an air cyst.

2:24

And so one or two or even three air cyst, I blow those off.

2:27

I just say, you know, these are probably post-infection

2:29

or post-traumatic PNE seals and you move forward

2:32

because if you were

2:33

to start thinking about diffuse cystic lung disease

2:35

and do a clinical workup in all those patients,

2:37

you'd be over calling left and right

2:39

and that's not doing a service to the patient,

2:41

to the clinician or even yourself.

2:42

Okay? So you gotta define, you gotta figure out for yourself

2:45

how many cysts is enough

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for your start thinking about diffuse cystic lung disease.

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Again, seven I think is a nice number.

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Also easy to remember when you're sure the patient is

2:54

diffuse cystic lung disease.

2:55

The first thing to think about is, is really

2:57

for me is dichotomous.

2:59

So is it LCH?

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If something is LCH long

3:04

and han cell histiocytosis, it looks

3:06

so different from the other cystic lung diseases.

3:09

I think it's quite specific

3:11

and I'll show you some examples of that in just a bit.

3:13

And I as I'll show you more examples, you'll say, okay,

3:15

I know what this Chung guy is talking about.

3:17

Right? So clearly LCH is sort

3:19

of an outlier in terms of CT morphology.

3:21

So I like to leave that out

3:22

and I like to actually think about that first.

3:24

Even though some would argue that for

3:27

significant diffuse tic lung disease LAM is sort

3:30

of the model that we should be using.

3:31

But again, just from a diagnostic standpoint, I like

3:33

to start with LCH because it looks

3:35

so darn different in most cases.

3:38

And then we consider lamb next

3:41

and then if it's not lamb,

3:42

we consider lymphocytic interstitial pneumonia

3:44

and the bird hug base syndrome.

3:47

So once you have excluded long hand cell histiocytosis,

3:51

which I'm gonna show you example of in just a bit,

3:53

this is the diagnostic workflow that I think that a lot

3:57

of people like to use.

3:59

Um, this is actually studied by Escalon

4:02

and Dr. David Lynch of the National Jewish Group in Denver.

4:05

This was published in 2019.

4:07

This works really well and I like it

4:08

'cause it's so darn simple.

4:10

So as I said before LCH we're gonna put aside,

4:12

I'll show you examples that a bit,

4:14

but once you exclude LCH,

4:16

this diagnostic workflow is is quite powerful.

4:19

So if it's a diffuse cystic lung disease

4:22

with these pretty thin wall cyst,

4:23

you start thinking about lymph al mitosis.

4:26

If it's a man, highly unlikely to be lymph banal mitosis.

4:29

Okay? If it's lower lump preponderant rather than diffuse,

4:33

you start to think about bird hug debase syndrome

4:35

and lymphocytic interstitial pneumonitis.

4:37

If you see a lot of these para mediastinal cyst

4:40

or a di disproportionate number of para mediastinal cyst,

4:43

you start to thinking about bird hug debase syndrome.

4:45

Especially if the hi patient has history

4:46

of solid renal tumors like renal cell carcinoma

4:50

or onco cytomas.

4:51

'cause we know OG base syndrome also predisposes patients

4:55

to developing renal tumors.

4:57

So that would point to BHD.

5:00

If it does not fill that criteria of paraia ssis,

5:03

then we start to think, well it's probably LIP.

5:05

But really it's, it's an indeterminant pattern though I

5:07

think in most cases it is LIP usually related

5:10

to Sjogren's syndrome.

5:13

And so, and I alluded to highly accurate,

5:15

especially if we're looking at lymphangitis mitosis,

5:19

which is, which is gonna be one of the more common patterns

5:21

that we're gonna be thinking about.