0:01

Alright, well cardiopulmonary imaging,

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we're going to do a session on the mediastinum,

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and this is going to be the radiographic

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approach to the mediastinum, session one.

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We'll have other sessions on the

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mediastinum with CT and maybe MR as well.

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So, I'm going to introduce the term

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vascular pedicle to you because it's

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something that I find very useful.

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It reflects intravascular fluid physiologically.

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I'm going to try to introduce also the concept

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of density and contour rather than width.

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I'm going to give you the four most

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common causes for wide mediastinum.

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None of them pathologic.

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And I'm going to emphasize to you and

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plead to you not to use the term wide

0:40

mediastinum on any of your reports.

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It causes anxiety and that's

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not what we are about.

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Okay.

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So let's take a look.

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Normal anatomy.

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This is the vascular pedicle, by the way,

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it is the superior vena cava into the right

0:55

atrium, superior vena cava, and your aortic arch.

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Please know.

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Research has shown there is no knob in the chest.

1:03

So do not say aortic knob.

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It, uh, it's really a low brow.

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It's an arch.

1:09

So the arch measured here to the superior

1:11

vena cava, that is your vascular pedicle.

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And your superior vena cava is very compliant and

1:16

it changes with your intravascular fluid volume.

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So as we go through this, you're going

1:23

to hear a lot of different things.

1:24

So just, he who joyfully marches to music and

1:27

rank and file has already earned my contempt.

1:29

He has been given a large brain by mistake since

1:31

for him, the spinal cord would have sufficed.

1:35

So let's, let's do a little brain thinking here.

1:37

The dogma, wide mediastinum.

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In the trauma setting, that's the means,

1:42

eh, there might be a hematoma, which may

1:44

mean it could be a great vessel injury.

1:46

So these are indirect signs.

1:49

When you use the term wide mediastinum,

1:51

clinicians get anxious, and when they

1:53

get anxious, they start ordering things.

1:55

So what about this concept?

1:58

A wide mediastinum in the trauma

2:00

patient is actually a good prognosis.

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Well, let's look into that.

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What is the mediastinum width

2:07

again, the vascular pedicle?

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What does that reflect?

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Intravascular fluid volume.

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You have a trauma patient who's laid out supine.

2:13

With increased flow from the legs, IV

2:16

pumping in normal saline or Ringer's

2:18

lactate or whatever their choice is.

2:21

Man, you better have a wide mediastinum,

2:24

a wide vascular pedicle.

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If it's narrow, what does that suggest?

2:28

They're bleeding out some.

2:30

So it's, it's, seeing a wide vascular

2:32

pedicle in the setting of trauma

2:34

is not necessarily a bad thing.

2:36

It's probably physiologically a good thing.

2:40

Okay, you can use the vascular pedicle or the

2:43

mediastinal width if you wish, but vascular

2:45

pedicle when you're looking at ICU patients.

2:47

Notice it's wider here in a patient with

2:49

pulmonary edema, congestive heart failure.

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After diuretics, and what does a diuretic do?

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It decreases the intravascular volume, your

2:57

mediastinum or vascular pedicle gets smaller,

2:59

and the fluid gets reabsorbed, and it's gone.

3:04

Rotation is a huge cause for a wide mediastinum.

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82 00:03:08,220 --> 00:03:09,170 What do I mean by that?

3:09

You look at your clavicles

3:10

medially and the spinous process.

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When you are rotated to the right, your superior

3:14

vena cava, which forms that right border, is then

3:17

thrown out far and the descending thoracic aorta,

3:20

which forms the left, is actually also thrown out.

3:23

So you actually widen it out.

3:25

What do I mean by this?

3:27

You look at this patient who's rotated to the

3:29

right, and you can see it's a wide mediastinum.

3:32

But that's the same person just a few

3:34

minutes later, we just did this because we

3:36

were bored, um, we threw someone on there,

3:38

and it narrowed the mediastinum when you

3:41

rotate to the left because you overlap them.

3:43

So rotation to the right will widen the

3:45

mediastinum. But that's not pathologic.

3:49

A tortuous thoracic aorta.

3:52

What do you, why does it get tortuous

3:54

or why does it unfold with age?

3:55

And no, it has nothing to do with hypertension.

3:58

It has nothing to do with compliance.

4:00

It has nothing to do with all of these

4:01

other things that people make up.

4:03

It is simply the fact that you

4:05

lose height as you get older.

4:07

You get kyphotic, lose height in your

4:09

vertebral bodies, and then as the

4:11

roof comes down, the aorta bulges out.

4:15

That's as simple as that.

4:17

But when it bulges out,

4:18

it can widen the mediastinum.

4:20

Lastly, mediastinal ligamentosis.

4:24

Body habitus has changed these days, people.

4:26

It's not the same as when I was a kid,

4:28

and I'm not lecturing, just observing.

4:30

And mediastinal fat is now commonly

4:33

seen, and it widens the mediastinum.

4:35

So, what does a wide mediastinum mean?

4:39

It means the vascular pedicle or

4:41

intravascular fluid volume is increased.

4:42

It means there is mediastinal fat.

4:44

It means the person is rotated to the right.

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Um, or there's a tortuous aorta or some combination.

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None of those are pathologic.

4:51

So, and, and Ho and all did a study at

4:53

Harborview and they looked with six blinded

4:57

radiologists at 30 trauma and 47 randomly.

4:59

And they only two criteria, one,

5:02

just your gestalt overall impression.

5:04

And two was the mediastinum wide.

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Was it wide?

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And look what the results were.

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They actually did much worse on trying

5:14

to figure out if the mediastinum was

5:15

even wide with a greater interobserver

5:18

variability of, uh, or lower inter or

5:21

increased interobserver variability.

5:24

So it is not a good sign anyway.

5:27

And when you use it, you make people

5:29

nervous and, uh, they think, and I agree,

5:33

medical education has ingrained the widely

5:35

promoted concept that mediastinum widening,

5:37

which is misleading and that we believe the

5:39

term causes confusion and should be avoided.

5:42

Concur.

5:43

What is a wide mediastinum?

5:44

It actually comes from 1976, concluded

5:48

that eight centimeters are greater than 25

5:49

percent of the thoracic cavity is abnormal.

5:51

And it was a really good study back then.

5:54

What has changed since 1976?

5:57

Well, a lot has changed.

5:58

The imaging technology, the body habitus of

6:01

generalized people, and even the trauma protocol.

6:04

Okay, so the old films, the narrow

6:07

latitude, black lungs, white mediastinal

6:11

blob, what criteria could we use?

6:14

Contour and width.

6:16

Nowadays, the, the, the latitude is much wider.

6:19

We see the different densities

6:21

within the mediastinum.

6:22

We can appreciate that, but we haven't

6:25

incorporated that in our teaching or

6:27

curriculum or in a way we approach our imaging.

6:30

So what do we do?

6:32

One, wide mediastinums are going to be

6:35

common in these trauma patients, mainly

6:37

because one, we're doing it differently.

6:41

In the old days, we used to put the

6:43

film screen right behind the patient,

6:44

they barrel roll and put them up.

6:46

Nowadays, we put the screen in the table.

6:50

So the patient to screen distance

6:52

is increased quite a bit.

6:54

We studied this at OHSU and we got about a 17

6:57

to 25 percent magnification of the mediastinum.

7:01

So this is what I would suggest.

7:04

Look at the density and contour,

7:06

ignore whether it's wide or not.

7:09

The aortic arch is your standard of reference.

7:12

That's your reference.

7:13

Look at the right side of the

7:14

trachea, the superior vena cava.

7:16

Is it the same density or is it less dense?

7:19

That's normal.

7:20

Is it the same density or higher?

7:22

That needs an explanation.

7:24

Okay, this is normal.

7:26

There's your arch.

7:27

There's your superior vena cava your vascular

7:29

pedicle Notice the arch will always be brighter

7:33

and more pacified because it's horizontal and that

7:36

superimposes the blood The superior vena cava is

7:41

vertical blood with air and fat on both sides.

7:44

So it should always be less It's

7:46

opaque than the aortic arch.

7:49

What about this one?

7:50

It's not a wide mediastinum,

7:52

but this density is too high.

7:54

It's greater than the aortic arch.

7:56

There's mass effect on the trachea.

7:58

This is blood.

7:59

This is abnormal.

8:02

How about this?

8:03

Can't see the arch.

8:04

The right side has contours that are

8:07

convex and it's brighter than the arch.

8:10

This is, this is abnormal.

8:12

If this is trauma, this is blood.

8:14

If it's an outpatient, this is adenopathy.

8:19

And then lastly.

8:20

It could still be normal,

8:22

but you can't see the arch.

8:23

It's completely dense.

8:26

Uh, there's mass effect on the NG

8:28

tube, the esophagus and the trachea.

8:30

This is a contained rupture or

8:32

a large mass in the mediastinum.

8:35

So, let's take you through it real fast.

8:37

Trauma patient.

8:39

What are, are we worried about the mediastinum?

8:41

Yes.

8:42

Density is too high.

8:43

It's convex.

8:44

Can't see the arch.

8:45

That's blood, blood, and blood.

8:48

This person, trauma, wide mediastinum.

8:51

I don't care.

8:52

The arch is here, but there's lots of fat.

8:54

I see the azigous vein.

8:56

There's no mass effect in the trachea, normal.

8:59

Patient rotated to the right, fell out of

9:01

her chair, CT because of a wide mediastinum.

9:04

It's a tortuous aorta, rotated to the

9:06

right, normal density on the right.

9:08

You see the azigous arch.

9:10

There's nothing pathologic here.

9:14

Don't even send them a CT.

9:16

Look at the mass effect on the trachea.

9:19

Look at the convexity of the AP recess.

9:22

The aorta is bright.

9:23

Can't even see it.

9:24

This is great vessel injury, period.

9:29

This person, what do you think?

9:31

Narrow mediastinum, not a good sign.

9:33

They were bleeding out, by the way, quite a bit.

9:35

And notice the right side of the mediastinum.

9:38

It's the same density as the arch.

9:40

There was actually a mediastinal hematoma here

9:42

from a burst fracture in the upper thoracic spine.

9:46

So, um, summary.

9:49

Use the mediastinum as, call

9:51

it the vascular pedicle.

9:53

That will look at intravascular volume.

9:56

Very helpful in ICU imaging.

9:58

Um, compare the density.

10:01

Look at the aortic arch.

10:02

What's the right side?

10:03

If it's the same density or

10:05

more, that needs an explanation.

10:07

And lastly, you can take

10:08

a look at the aortic arch.

10:10

Is it brighter?

10:11

Is there a mass effect around it?

10:12

That also needs an explanation.

10:14

I implore you to try to avoid

10:16

the term wide mediastinum.

10:17

If you find the mediastinum suspicious,

10:20

say it's an indeterminate mediastinum

10:22

or something along those lines.

10:24

With that, thank you very much.