0:00

We're back with our 69-year-old

0:02

man with known bladder carcinoma.

0:04

We've got a CT with contrast, slightly

0:07

different phase than the one in the

0:08

middle from 2017, a little bit earlier.

0:11

Contrast enhancement phase 2019, and then an axial,

0:16

which we'll probably set aside for right now from 2019.

0:20

I want to talk a little bit about size

0:22

and enhancement with my colleague, Dr. Finazzo.

0:24

11 00:00:25,689 --> 00:00:29,060 And on the left, we see there was a

0:29

low-density lesion in the midpole of the right

0:32

kidney that has either disappeared or is less conspicuous

0:37

in 2019. Perhaps it changed character a little bit.

0:41

The one in the upper pole got bigger, for sure.

0:45

There it is.

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And it also clearly changed character.

0:49

And then the one in the left upper pole, that

0:51

was pretty big and nice and round and juicy.

0:54

That one shrank dramatically, produced

0:57

a scar and a funny-looking pseudomass

1:00

in the upper portion of the left kidney.

1:02

There's no real mass lesion there.

1:04

So I just want to make the point that,

1:06

number one, pure size doesn't intimidate me.

1:09

As long as the lesions are smooth and they

1:10

meet criteria elucidated for Hounsfield

1:13

unit measurement and enhancement.

1:16

And I don't see any papillary projections.

1:19

Change in size also doesn't intimidate

1:21

me for the same reasons.

1:23

In other words, lesions can get bigger, lesions

1:26

can get smaller, and they can get bigger

1:27

and smaller in a very short period of time.

1:30

So pure size and pure size change is not

1:34

a very strong criterion to go chasing a

1:36

lesion with some other procedural mechanism.

1:41

The other thing I want to talk about

1:42

and ask you about is enhancement.

1:44

How can you use the dynamics of

1:46

enhancement and what are the pitfalls?

1:51

So when we speak on CT, as we talked about

1:54

earlier, many times we're just given either just

1:57

the non-contrast or the post-contrast imaging.

2:00

So teaching point number one, if you have a non-

2:03

contrast scan, and you can clearly see, confirm it's

2:07

a simple cyst being Hounsfield unit measurement with

2:10

region of interest less than 20, you can let it go.

2:13

And if you can see Hounsfield units greater

2:15

than 70, you can say it's a hemorrhagic cyst.

2:18

You can let it go.

2:19

The ones in between you need to work up.

2:21

When you measure the Hounsfield units in a

2:25

mass in the unenhanced, you want to get

2:28

a big region of interest, and that's different

2:31

in comparison to when we look at areas

2:34

of enhancement, which we'll get to later.

2:37

But if, on MRI and on just renal masses in

2:40

general, on post-contrast, we'll come back to that.

2:44

But when we are only faced with post-contrast

2:47

imaging, what are some of the tricks we can use?

2:51

First of all, measurement of lesions

2:54

should be done in the nephrogenic phase.

2:58

Because that's number one, our first step.

3:01

Best chance to identify a mass if it's

3:04

a solid mass, and number two, look at areas

3:07

where it could potentially enhance, and so

3:10

define nephrogenic phase for our audience.

3:11

So nephrogenic phase, really we want to look at lesions

3:12

71 00:03:14,774 --> 00:03:18,055 between the two and four minutes post-contrast.

3:18

And when we're given an opportunity to have a

3:21

delayed phase, to measure enhancement, you could

3:25

look at, the enhancement in the delayed phase.

3:29

And similar to Hounsfield units,

3:31

it's a relative measurement.

3:32

You count the Hounsfield units post-contrast,

3:35

you subtract that from the nephrogenic phase.

3:37

And if you have more than a 15 percent,

3:40

15 number drop in region of interest measurement in

3:44

the delayed minus the nephrogenic phase, then

3:48

you can say that the lesion is in fact enhancing.

3:55

But beware, there are pitfalls; if

3:58

you don't catch the mass at peak enhancement,

4:01

you can underestimate enhancement.

4:04

So just to summarize, you measure in the

4:05

nephrogenic phase, somewhere in the 2-4 minute

4:08

range, and then you measure later than that, in

4:11

the delayed phase, and if you see an HU drop,

4:14

a Hounsfield unit drop of 15 or more, or, you

4:17

know, that would, that would say what to you?

4:20

That the lesion is enhancing, that there

4:22

is enhancement in that lesion and that would

4:24

be considered more worrisome and not just a cyst.

4:27

So

4:27

that would be an indirect way to evaluate

4:30

the Hounsfield character of a lesion if

4:32

you just have a contrast-enhanced CT.

4:34

Now, let's say you do an ultrasound, you're

4:37

a radiologist, you do an ultrasound, you see

4:39

something that's indeterminate and you know you're

4:41

going into the CT for that specific purpose.

4:44

Then, as a practitioner,

4:46

you should be getting a pre-contrast

4:49

and a post-contrast from the get-go.

4:51

You should be instructing your technologist.

4:53

But a lot of times, you don't know.

4:54

You find these incidentally.

4:56

You have only a contrast.

4:58

So this is a little trick that

4:59

you can use to help yourself.

5:00

That's right.

5:01

Alright, Pomeranz and Finazzo out.