0:01

So we talked about NSIP and let's talk about fibrotic hp.

0:05

And so here's a table from the diagnostic guidelines

0:09

for HP diagnosis.

0:10

And this is a table for fibrotic hp.

0:14

And so really the most important part of this is

0:17

that high confidence pattern.

0:18

So there's typical fibrotic HP pattern.

0:22

So bottom line, what is this? What is it?

0:24

What are we looking for? We're obviously looking

0:26

for fibrosis on HRCT 'cause it's fibrotic hp.

0:30

So things like reticulation, traction bronchiectasis

0:34

or bronchiectasis subpleural humming.

0:36

Combining architectural distortion, you need

0:38

to have fibrosis bottom line

0:40

because it's defined as fibrotic.

0:42

And then you wanna see at least one abnormality indicative

0:44

of small airway disease.

0:45

So central ular nodularity,

0:47

often a ground lasts attenuation, mosaic attenuation

0:51

or three density pattern or the air trapping sign.

0:54

I'll show you what the three density pattern is

0:56

in just a little bit.

0:57

But bottom line, it is just a manifestation

0:59

of air trapping plus some infiltrative abnormalities,

1:02

some inflammation and or fibrosis within the lungs.

1:06

And then there are different criteria out there,

1:09

but I, I like to think about distribution as well.

1:11

I think there is signal within distribution for fibrotic hp.

1:14

And so many of these cases, not all,

1:17

but many of these cases are gonna have diffuse

1:19

distribution in both the axial

1:21

and the superior inferior planes

1:24

or they're gonna be mid-upper lung preponderant

1:27

or some people will just call it basal sparing.

1:29

So mid-upper lung preponderant

1:31

or mid lung preponderant if you have these distributions,

1:35

any one of these distributions which would be really

1:37

atypical for UIP and frankly atypical for NSIP as well.

1:41

You start thinking about typical fibrotic hp

1:44

and you really start digging for any findings

1:47

of small airway disease as defined in number two.

1:51

So here are two separate patients in chrono plane.

1:55

And so both these patients clearly have pulmonary fibrosis.

1:57

The one on the left has more fibrosis, the one on the right,

2:00

but the patient on the right,

2:01

I think it's pretty clear the patient has some reticulation

2:04

here, especially in the peripheral portion of lung.

2:06

Little bit of pleural parenchymal scarring

2:07

there at the left lung apex.

2:09

But what I wanna point out are these yellow arrows.

2:11

I probably could have put a lot more

2:12

yellow arrows on this patient.

2:14

But bottom line, these are areas of mosaic attenuation.

2:17

These dark areas and these are all areas of air trapping.

2:20

We don't call it air trapping on an inspiratory ct.

2:23

We only call it things air trapping on expiratory ct.

2:26

But on these inspiratory cts we would call these areas

2:29

of mosaic attenuation

2:31

and on expiration, if we think they're air trapping,

2:34

if they stay as dark as hypodense as they do on expiration,

2:38

as on inspiration, then by definition we've identified areas

2:42

of air trapping.

2:44

Note the diffuse distribution in the right hand

2:47

image here of fibrosis.

2:48

And on the left hand image, I think it's pretty clear

2:50

that fibrosis is really concentrated in the upper

2:53

and mid lung zones with relative basal sparing.

2:56

More examples here of high competence

2:58

Fibrotic hp.

3:00

So typical fibrotic HP pattern.

3:01

Beautiful example here of some mild reticulation,

3:04

some mild traction bronchiectasis in some areas

3:08

and some underlying ground.

3:10

Last opacity mosaic attenuation again noted.

3:12

So mosaic attenuation being defined

3:14

as these low density areas with polygonal shape.

3:18

So these are secondary pulmonary lobules.

3:20

Sometimes a combination

3:21

of multiple secondary pulmonary lobules superimposed on each

3:24

other and these likely represent air trapping.

3:27

Well, how do you tell? Well you do the exhibitory series

3:29

and so we see that these areas

3:31

of hypo density are accentuated

3:33

because the more normal lung has let go

3:36

of the gas and have turned more gray.

3:38

So in this setting, obviously the more gray lungs,

3:40

hyperdense portrait lungs are normal

3:42

and the hypodense areas of lungs are actually abnormal.

3:46

So fibrotic hp, another example here, fibrotic hp.

3:50

Beautiful example here.

3:51

Upper lung preponderant disease,

3:53

clear mosaic attenuation shown to represent air trapping.

3:56

Lung bases are almost completely spared except

3:59

by mosaic attenuation, which again was shown

4:01

to represent air trapping.

4:02

These all kind of start to look the same, don't they? Right?

4:04

So another patient here with pulmonary fibrosis,

4:07

this patient actually has a little bit more

4:08

basal predominant disease.

4:09

And so I'll tell you, even though this,

4:13

the distribution is not quite right for fibrotic hp,

4:16

if I was speaking to my clinician

4:17

because of the degree of mosaic attenuation

4:20

and the superimposed ground lass opacity

4:23

and then on expiration noting that all these areas

4:25

of mosaic attenuation are actually air trapping.

4:27

So air trapping on expiration

4:29

mosaic attenuation on the inspiratory image,

4:31

I would tell my clinician,

4:33

even though the the distribution is not quite right

4:35

for fibrotic hp, um, this is high confidence HP in my mind

4:38

and we should move in that direction.

4:40

Look for antigens which are causing fibrotic hp, which

4:43

as you guys know in the US and,

4:46

and most parts of the western Europe,

4:47

and I think Asia as well I think can be pretty confident

4:50

saying that most causes

4:52

of hypersensitivity immunized are gonna be

4:54

to molds and birds.

4:55

And there are other causes as well, like, so in, in Denver,

4:58

one of the common causes are not common causes

5:01

but not uncommon causes, especially

5:02

during the wintertime was hot tub lung.

5:04

So I dunno if you guys heard of this,

5:06

but very interesting pattern here.

5:07

So in Denver, what do you do during the wintertime?

5:09

You go up to the mountains, you go skiing or snowboarding.

5:12

And so afterwards, because we're, we're all sort

5:14

of outta shape now, at least I am, I'm middle aged,

5:16

what do you do to sort of rest your,

5:18

your sore muscles and your sore knees?

5:20

You go into that hot tub

5:21

and that hot tub has probably not been cleaned since 1992.

5:24

And so there's all this weird stuff in there.

5:26

You know, chlorine doesn't kill everything, right?

5:28

It just doesn't. And heat doesn't kill everything.

5:29

In fact, heat sometimes will create the right milieu

5:32

for weird bacterias to form and grow.

5:35

And so in hot tubs what likes

5:36

to grow there are these weird like gram negative rod species

5:39

and nontuberculous microbacterial species will grow in

5:42

that cesspool of stuff.

5:44

And then as the water sort of boils off

5:46

and steams, uh, people oftentimes will weave that in,

5:49

especially 'cause you know, you kind of like dip down into

5:51

that hot tub and you breathe all that in.

5:54

And so those antigens can actually cause

5:56

A pretty severe hypersensitivity pneumonitis.

5:59

So again, it's, that's not a mold, right?

6:01

It's not a bird, but it's not uncommon.

6:03

Depends where you live and what you guys do

6:05

and what you guys are exposed to, right?

6:07

So if you googled hypersensitivity,

6:09

pneumonitis probably get like a hundred different things

6:11

that can cause hypersensitivity pneumonitis.

6:14

But again, just for, I mean testing and purposes

6:18

and for the purposes in, in most clinics

6:20

that don't have a lot of hot tubs

6:22

or other types of exposures, it's gonna be mold and birds.

6:26

Alright? Another example here of fibrotic hp,

6:29

this is not okay, I repeat not a high confidence pattern

6:33

of fibrotic hp, but I bring this up

6:36

because I just wanted to kind

6:38

of remind the audience of this.

6:39

So this is actually a UIP pattern of pulmonary fibrosis.

6:42

Here's the axial plane, here's the coronal plane.

6:44

So clearly peripheral, clearly based is predominant,

6:46

not the best coronal, but I just want

6:48

to bring this up in terms of the distribution.

6:50

And so this is just to remind everyone that

6:54

even if we don't have a high confidence pattern

6:57

of hypersensitivity pneumonitis, we cannot exclude hp.

7:02

I've heard people look at, look at a CT like this

7:05

and say, oh, well this is UIP, it can't be hp.

7:07

There's no way this is fibrotic hp.

7:09

And that is actually a very wrong statement.

7:12

And so that sort of ignores the sensitivity

7:15

and specificity profile of HRCT in the setting

7:18

of interstitial lung disease.

7:20

And so as a general rule

7:24

in HRCT, specificity can be quite high, like

7:28

above 90% if you have all the classic findings

7:32

of a specific subtype of pulmonary fibrosis.

7:35

Again, there are some exceptions to this rule,

7:38

but as a general rule, this, this holds.

7:41

So if it's one of these patterns where you're like, oh,

7:43

I'll eat my hat if it's not that thing,

7:44

that's why we made a big deal about a high competence

7:47

patterns in our practical approach, right?

7:49

So if it has the high compass pattern,

7:52

specificity is gonna be very high.

7:53

And so accuracy is gonna be very high.

7:55

Again, if it has the high compass pattern,

7:57

if it doesn't have that specific pattern,

7:59

you can really never rule out a

8:01

different type of pulmonary fibrosis.

8:03

You can never look at an UIP pattern, say,

8:05

this patient does not have fibrotic hp, you know this,

8:08

this patient doesn't have connect tissue disease.

8:09

You can't do that, right? We need to go

8:11

to multidisciplinary diagnosis, discuss it

8:14

with our pathologist with if we have pathological data,

8:18

discuss it with our pulmonologist, look at the serologist.

8:20

Really do like the full core press workup to try

8:23

and figure out what the best disease is for

8:26

that patient in the setting of pulmonary fibrosis.

8:29

And so with that, I just wanted to reiterate

8:32

what our practical approach was.

8:34

Remember, it's really easy, number one,

8:38

is it typical UIP or problem UIP?

8:40

If it's not that, then number two, you ask ourselves,

8:42

is it a, I will eat my hat if it's not this

8:45

thing NSIP pattern.

8:47

So high confidence NSIP pattern,

8:48

high confidence fibrotic a HP pattern

8:50

or a high confidence sarcoidosis pattern,

8:52

which I'll show you in the diffuse nodule lung disease.

8:55

And if it's not one of those two

8:56

things, we go to step three.

8:57

Step three is essentially punting with an indeterminate

9:00

for UIP pattern or calling an alternative diagnostic

9:04

category, which essentially is saying it does not feel like

9:06

UIP does not look like UIP looks like something else.

9:10

But maybe you can't put your exact finger on the exact

9:13

diagnosis or imaging pattern.

9:15

Okay? Three step pattern. Very, very simple in my mind.

9:19

Just an algorithm. Thank you so much.