0:50

Good afternoon, everybody, and, um,

0:52

uh, welcome to the case-based review.

0:54

So we'll get started right away.

0:57

Uh, the goal is to try and show case examples

0:59

of clinical scenarios, you know, that we need

1:02

to be aware of as majors, especially those

1:05

where we can make an impact and difference.

1:07

And I'm also going to provide some take-home points so that

1:10

you can take those and use them in your clinical practice.

1:16

So the first case is, um, it's actually a two-part case.

1:21

I'm going to show you two patients, uh, two different

1:24

patients who, uh, have a very similar clinical presentation.

1:28

And they both have the same primary disease entity.

1:32

So the first one is a 52-year-old female

1:35

patient who is known to be hypertensive,

1:38

has diabetes, longstanding diabetes,

1:41

and has been experiencing right upper

1:42

quadrant pain for the past three weeks.

1:45

The pain is not related to eating, and she doesn't

1:48

have any blood per rectum, diarrhea, or constipation.

1:52

So let's dwell into the images.

1:54

So looking at the axial contrast-enhanced images,

1:58

and you can see oral and IV contrast has been given.

2:01

So as I'm going to scroll through these, um,

2:04

you can see there's a little bit of ascites,

2:05

in the liver, maybe some fatty infiltration,

2:08

uh, in the liver parenchyma itself,

2:11

a little bit of peritoneal stranding.

2:14

And you can see right here, the small bowel

2:16

mesentery showing a little bit of stranding as well.

2:19

As we march our way down, contrast-filled

2:22

uh, small bowel loops, and we start getting

2:26

into the area of the bowel that is abnormal.

2:29

So what you're seeing here is

2:31

basically the bowel is not distended.

2:34

Um, there is no, uh, mucosal thickening, uh, because if

2:41

you have linear or nodular mucosal thickening, then that

2:44

has a certain differential, or if you have, um, dilatation

2:49

that goes along with it, that has a certain differential.

2:51

So again, ascites.

2:53

What you're seeing is thickening of, um, uh, you're

2:57

seeing basically, uh, low-density thickening of

3:02

the submucosal layer of the bowel wall, which is

3:04

referred to as the "water halo sign," if you will.

3:08

So these are the axial images.

3:09

Now let me show you the coronal, and again,

3:13

scrolling through this, you are seeing the

3:15

distal jejunum, essentially the area of bowel

3:18

that is affected, a fairly long segment of bowel.

3:22

Again, no nodular or linear mucosal thickening.

3:25

There is no distension, but there is,

3:28

uh, the so-called water halo sign, or

3:30

low-density thickening of the bowel wall.

3:34

And again, has, uh, ascites to go along with that.

3:37

And there is a little bit of mesenteric, uh, stranding

3:40

with prominence of the, of the Vasa Recta.

3:45

So that's sort of the first patient.

3:47

You're seeing the axial and coronal images.

3:50

Again, these are just the summary images showing

3:52

the finding on the axial and the coronal, uh, plane.

3:56

The second patient is a 46-year-old woman who has

4:01

a longstanding history of recurrent abdominal

4:03

discomfort that has led to multiple hospitalizations.

4:08

And now she comes back with the same

4:10

complaint and gets admitted this time over.

4:13

So she has severe abdominal pain.

4:15

Again, there is no history of, uh, any, uh, passing any

4:19

blood or any vomiting or nausea, just severe abdominal pain.

4:23

So let's look at the axial image of this

4:26

particular patient as we march our way down.

4:28

Again, oral

4:29

and IV contrast has been administered.

4:33

So compared to the prior patient, this patient has,

4:37

um, a thickening of the stomach wall, which again is

4:40

low density or sort of fluid in density, if you will.

4:44

There is ascites in this patient as well.

4:47

And again, compared to the prior case where the

4:49

predominant finding was in the distal small or in the

4:52

distal jejunum, in this case, it is the duodenum, the,

4:56

the, the, uh, the second, third, and fourth part of the

4:58

duodenum leading into the jejunum, where you see the

5:01

abnormal finding. And this is the classic water halo

5:04

sign where there is thickening of the submucosa with

5:07

low density seen in the, um, in the wall of the bowel.

5:11

Again, there is some ascites to go along with it.

5:13

So that's on the axial.

5:15

Let's see on the coronal images.

5:18

The same finding you can see here is the duodenum, the

5:21

duodenal C-loop as it makes its way to the duodenal or

5:23

jejunal junction, and the classic low-density within the

5:28

bowel wall, which is thickened, but there is no dilatation

5:31

and no linear or nodular thickening of the mucosal folds. So

5:36

and again, there is some ascites in this patient as well.

5:40

Here's just a 3D image showing the,

5:43

um, the same again, the summary.

5:45

So these two patients, we have the first patient

5:47

where the predominant finding is in the distal

5:50

jejunum, the second patient where it is the duodenum

5:53

and the proximal jejunum, which are affected.

5:56

Now, as I mentioned to you, when you have

5:58

water halo, or you see low-density bowel wall,

6:03

um, it's important when you look at a bowel

6:05

and approach a patient with a bowel, as I said,

6:07

you want to make sure there is no dilatation or

6:10

distention, which these two patients don't have.

6:13

Then do you have linear or nodular thickening?

6:15

Because that leads to a certain differential,

6:17

which these patients don't have.

6:19

And then comes the question of having, um, thickening

6:22

of the submucosal or the bowel wall and, and

6:26

depending on the, um, on the density we see on CT.

6:30

So low, low density, as you see here, which is

6:33

called the water halo sign typically has the

6:37

two I's as the, um, differential, which is

6:40

inflammatory, uh, etiologies or ischemic etiologies.

6:45

Uh, then it can be pus in which case it's infection, or it

6:50

can be blood in which case there is bowel wall hemorrhage.

6:53

which is slightly more higher in density

6:56

than what you're seeing in these cases.

6:58

And then finally, it can be cells, and

7:00

which is typically seen in lymphoma.

7:03

Now, you know, of those entities, as I said,

7:05

this is low density, so it's water halo, which

7:08

means it's either ischemic or inflammatory.

7:11

It's too long a segment typically, and proximal

7:14

small bowel ischemia is not as common as it

7:16

is in the distal bowel or in the large bowel.

7:20

So, you know, that makes ischemia lower on the differential

7:23

and neither of these two patients has had any intervention.

7:27

And so that leaves, leaves, leaves us with inflammation.

7:30

So the question is can we resolve the etiology of the water

7:36

halo sign in these two patients in terms of inflammation?

7:41

Uh, can it be Crohn's or inflammatory bowel disease?

7:43

Again, the distribution is a little atypical.

7:46

That typically happens distally in the

7:48

small bowel as opposed to proximally

7:50

in the, uh, in the small bowel.

7:53

So let's look at the history a little bit.

7:55

Case A, this patient was, I told

7:57

you, was a diabetic and hypertensive.

7:59

So she has been taking an ACE inhibitor for hypertension.

8:04

And case B, which is the second case who

8:06

has been getting recurrent episodes, has

8:08

a brother who has a similar condition.

8:11

He gets a rash and abdominal symptoms.

8:14

And then in addition to the abdominal pain, she

8:17

also gets swelling in the tongue on separate occasions

8:20

and also gets a rash that, that accompanies it.

8:24

So given the history in these two different

8:27

patients, the question is in terms of differential

8:30

diagnosis, which do you think is the most common,

8:34

um, or most likely diagnosis in these two patients?

8:38

So you have these five options: Crohn's enteritis,

8:42

infectious enteritis, angioedema of the bowel

8:45

wall, bowel wall metastasis, or lymphoma.

8:48

All right.

8:50

So a hundred percent got it right.

8:51

It is angioedema of the bowel wall.

8:53

And, um, again, the water halo sign, typically with

8:57

the history in these two different, uh, different

8:00

patients, uh, the same etiology, which is angioedema.

9:03

And if you look at the classification of angioedema,

9:07

you can see that it can be, uh, acquired in

9:10

which case medications are the commonest one we

9:13

see in our emergency setting and ACE inhibitors.

9:16

are the most common, although NSAIDs

9:18

are, NSAIDs can also lead to it.

9:21

If it is hereditary, it's because of C1, um,

9:24

uh, you know, enzyme, um, uh, C1 esterase,

9:30

inhibitory enzyme deficiency, which leads

9:32

to, um, uh, the, the symptoms that we see.

9:35

And typically they have skin rash as well as,

9:38

um, you know, recurrent bouts that happen, which

9:41

was seen in the, in the, in the second patient.

9:44

Irrespective of what is the etiology in terms of,

9:47

you know, whether it's idiopathic, it's secondary

9:49

to medications, or is it a, a hereditary angioedema,

9:53

the underlying mechanism is increased capillary

9:56

permeability, which leads to, um, edema of the bowel wall.

10:00

And ultimately that is what is

10:02

seen as the, uh, water halo sign.

10:04

The important point to remember is, uh, that although

10:08

the diagnosis is clinical awareness of this entity.

10:11

is, and its characteristic imaging appearance can lead or

10:15

sway the, uh, uh, the, uh, clinicians to this particular

10:19

diagnosis when the radiologist raises the concern.

10:22

And although imaging follow-up may not usually be

10:25

indicated, um, complete remission of the abnormal findings

10:28

may support the clinical diagnosis of, uh, angioedema.

10:32

So that's sort of in a nutshell.

10:33

So the take-home message here is if you

10:35

get proximal small bowel water halo sign,

10:38

correlate with the history and think of.

10:41

angioedema, whether secondary or

10:43

hereditary in the differential diagnosis.

10:45

So that was the first case.

10:46

Excellent.

10:47

We move on to the second case.

10:49

Second case is a 57-year-old male patient who

10:53

comes with abdominal pain and microhematuria.

10:56

And as is the case in a lot of instances, you

10:59

know, an ultrasound is asked and I'm going

11:01

to show you the ultrasound static images.

11:04

So we are looking at the right. There's no hydronephrosis,

11:07

looks like the right kidney is fairly unremarkable.

11:10

There are no stones we see, no masses, no cysts.

11:14

And then we come to the left side.

11:15

Compared to the right side, you can see, if you

11:18

see the outline of the left side, there appears

11:19

to be dilatation of the collecting system.

11:22

And there appears to be a hypoechoic

11:24

lesion centered in the renal sinus.

11:27

And if you put the Doppler flow on,

11:28

it's not a very vascular lesion.

11:31

You can see vessels around it, but not typically within it.

11:35

You know, a little bit of flow at the periphery,

11:37

but really not a very hypervascular lesion.

11:40

But clearly there is hydronephrosis and dilatation of

11:42

the collecting system, as you're seeing in these images.

11:47

And so, you know, he has microhematuria, has abdominal

11:51

pain, and the question is what is causing, uh, the

11:54

dilatation of the collecting system on the left?

11:56

And what is the reason that you're seeing

11:59

that hypoechoic area in the left renal sinus?

12:02

Okay.

12:02

And so because of those reasons, the

12:04

patient gets a hematuric protocol CT.

12:07

And so what I'm showing you on the, on the left

12:09

is the, um, uh, is the contrast-enhanced images.

12:13

The image on your right are the delayed,

12:15

delayed, uh, nephrographic, um, uh, phase images.

12:19

So a little bit of blunting of the, um, of

12:22

the window level so that you can appreciate

12:23

the filling of the collecting system.

12:25

So as we march our way down, you can see that there is

12:29

clearly an infiltrative mass, uh, that is present, centered

12:34

in the renal sinus, and you can see the parenchyma,

12:39

a normal parenchyma on the periphery, is enhancing.

12:43

You can see the right kidney is

12:45

showing excretion of contrast.

12:46

There is paucity of excretion of contrast on

12:49

the left, and you can see that the mass extends

12:53

beyond the renal sinus into the proximal ureter.

12:56

You can still see there is enlargement of the, uh, the

12:59

ureteric lumen there with filling defects seen within it.

13:03

And as we come down, you can see that there

13:06

is now the ureter becomes normal in caliber.

13:09

So I'm going to show you the coronal

13:11

images where it's a little bit better seen.

13:12

In addition, if you look on the axial images,

13:15

there also is an enlarged lymph node in the left

13:19

common iliac location and also a few scattered

13:22

small nodes higher up, which are not enlarged, but

13:24

the largest is seen in the common iliac location.

13:27

Immediately distal to the point where the ureter is

13:30

transitioning to, uh, from the enlarged to normal caliber.

13:33

And these are the coronal images showing the

13:35

same, the portal venous and sort of the, um,

13:38

the delayed excretory phase, if you will.

13:41

And again, you can see that the infiltrative mass

13:44

originating in the renal sinus, uh, extends to the, uh,

13:47

parenchyma, uh, and also extends into the proximal urethra.

13:52

Here is the enlarged node that we saw on the axial image.

13:55

And here it is on delayed.

13:56

You can see that there is contrast excretion on the

13:58

right, but there is no perceptible contrast seen in

14:02

the collecting system on the left, indicating that

14:05

clearly this mass is compromising the renal function.

14:08

The renal vein appears to be normal in caliber.

14:10

There is no extension into the renal vein.

14:13

So all we see in summary is an infiltrative mass.

14:17

Which is, um, sort of, uh, centered in the renal sinus,

14:21

is encroaching on the renal sinus, obliterating the renal

14:25

sinus, is causing obstruction to the renal collecting

14:28

system on the left, compromising the renal function.

14:32

There is a small little stone here, which is, you know, just

14:34

probably an incidental thing seen in the left upper dilated

14:36

upper polar calyx, and there is accompanying adenopathy.

14:40

There is no extension into the renal vein.

14:41

So those are some of the summary of the findings.

14:44

And given that this patient has not frank,

14:47

but microhematuria and abdominal pain, the

14:49

question is what is your most likely diagnosis?

14:52

So these are the options,

14:57

renal cell carcinoma, transitional cell carcinoma,

15:00

some kind of chronic renal infection or lymphoma.

15:07

So the majority of you, um, thought about transitional

15:10

cell carcinoma and about 15 percent thought about lymphoma.

15:15

Now, it's interesting, um, you know, if you look

15:17

at the size of the lesion that is infiltrating the

15:20

renal sinus, um, one would expect, uh, typically

15:25

with transitional cell carcinomas to have frank

15:27

hematuria, which this patient didn't have.

15:28

Now, that's not a, you know, it's not a distinguishing

15:32

feature, but that should lead you to the, to the

15:34

fact that something else perhaps is going on here.

15:37

And the correct answer is lymphoma.

15:40

Although, you have to give a differential and this

15:42

patient ideally needs to have tissue sampled to make

15:45

the answer or to, to arrive at the correct answer.

15:48

This patient did have a nephroureterectomy and I, I'm

15:50

going to tell you a little bit about why that was done.

15:53

Uh, and, and this turned out to be follicular lymphoma.

15:56

Clearly, you can see that the mass is sort of

15:58

arising in the renal pelvis and ex, was extending

16:01

fairly low down into the, um, uh, into the ureter.

16:05

So when you look at the differentials of infiltrative

16:07

renal masses, uh, you know, this was, somebody

16:10

has actually looked at that and what they found

16:12

was the overwhelming majority was between renal

16:15

cell carcinoma and transitional cell carcinoma.

16:17

Those two would be the commonest

16:19

infiltrative renal masses that you would see.

16:22

But the, but lymphoma is a distinct third and you know,

16:25

it's important to keep that in mind and, and sort of,

16:28

uh, mentioned that in the differential, if, if somehow

16:33

the clinical symptoms or the clinical features don't fit

16:36

or something else is going on, which doesn't make sense.

16:39

And then metastasis is being the least common.

16:41

So, you know, keep in mind about lymphoma.

16:44

And so in terms of taking home point is

16:46

don't forget lymphoma in the differential

16:48

diagnosis of infiltrative renal masses.

16:50

Now, biopsy may help.

16:52

Now, this patient interestingly presented in the last

16:55

week of March. And, you know, there was a time when

16:58

COVID things were sort of evolving and, uh, the, the

17:02

surgeons were apprehensive that if they waited for a

17:04

biopsy and if the patient didn't get a biopsy and, and

17:07

this was indeed a transitional cell carcinoma, then

17:10

he would have probably, um, the lesions would have,

17:13

the lesion would have spread and perhaps become, uh,

17:17

inoperable at that point and therefore a biopsy was not

17:21

done and they went straight to a nephroureterectomy.

17:23

One could make the argument if they had biopsied and

17:26

found it to be a lymphoma, the, you know, they could

17:28

have spared the surgery, but in this case, um, I, what,

17:32

which I didn't show you was a split renal function.

17:34

Um, nuclear medicine study was performed on, there was

17:37

barely any renal function on the kidney on that side.

17:40

And so it wouldn't have helped much, even if

17:42

they had found a diagnosis of lymphoma, they

17:44

probably would have taken the kidney out.

17:46

But under normal circumstances, you know, that is one

17:49

indication for doing a renal biopsy is if you see, if you're

17:52

suspecting lymphoma because clearly that can be managed non

17:55

surgically, uh, rather than doing an aggressive surgery.

18:00

But the bottom line is, you know, if

18:01

you have an infiltrative lesion, keep

18:03

in mind RCC, TCC are the commonest.

18:06

Don't, uh, don't forget lymphoma in the differential.

18:11

Alright, moving on to the next case.

18:13

This is a 58-year-old, uh, uh, female patient who comes to

18:17

the emergency room with persistent lower abdominal pain.

18:20

It's dull, aching, uh, is not related to

18:24

eating, is not related to, um, any kind of

18:26

exercises, just there throughout the day.

18:29

And she was worried what was going on.

18:31

So let's look at the CT images.

18:33

So let's start with the axial first.

18:36

So, um, and you can see this is, you know, sort

18:39

of a, um, uh, hematuria, uh, dual, uh, split

18:43

bolus, uh, study where, um, part of the contrast

18:47

has been given earlier to pacify the collecting

18:49

system because we were not sure what to expect.

18:52

And so there's contrast excretion here and

18:54

also enhancement of the parenchymal organs.

18:56

And so as we march our way down.

19:00

You can see that there is a large low-density lesion.

19:03

You can perhaps appreciate some septation if

19:06

you window it within this lesion and they,

19:10

they likely are showing some enhancement.

19:14

Here's the uterus.

19:16

You can see the sigmoid right here.

19:18

And, um, These are the round ligaments on either side.

19:21

So the question is, and you can see the ureters are coming

19:24

all the way, um, to the bladder and they seem to be, uh,

19:28

And so it is, you know, a, a mass that is arising from

19:33

the renal pelvis, uh, extending up into the lower abdomen.

19:37

Uh, we couldn't identify the, the, uh, ovaries.

19:40

So the assumption is being a, uh, you know, middle-aged

19:44

woman, this likely is a, um, adnexal or primary ovarian.

19:48

pathology.

19:48

Here is the coronal showing the same thing.

19:52

A large low-density mass which is arising

19:56

from the right sort of right adnexal region.

19:59

It's causing some extrinsic compression of the bladder.

20:03

Again, you can appreciate the subtle

20:05

septations which are likely enhancing.

20:09

And there's no obstruction to bowel.

20:12

We don't see any changes of bowel wall thickening

20:15

or anything within large bowel and a good amount

20:17

of contrast has been administered as you can

20:19

see there's adequate opacification of both

20:22

the small and large bowel in this instance.

20:24

And here is a sagittal image again showing its

20:27

relationship to the uterus, um, causing

20:30

an extrinsic, uh, compression. You can see it's

20:33

causing extrinsic compression on the bladder.

20:35

And again, the septations are seen nicely.

20:37

So that's sort of in a nutshell

20:39

what was seen on the, in the CT.

20:42

So the question is, um, what is the

20:44

site of origin of the lesion seen on CT?

20:47

And that should be a fairly straightforward and easy answer.

20:50

Let's see what

20:54

in a low-density lesion arising from the pelvis with

20:57

septations that seem to be enhancing we don't see any

21:00

neural nodularity or any kind of neural enhancing nodule,

21:11

okay, so 100 percent got it right it's the it is an

21:13

ovarian mass. And, you know, that was a fairly easy ask.

21:18

Um, so, uh, subsequently, we performed an MR

21:22

just to get a better, um, you know, better

21:26

assessment of the morphology of the lesion.

21:28

And as opposed to CT, you can see on MR, this is a CT scan.

21:31

fat-saturated T2-weighted image.

21:33

You can nicely appreciate the septation within the mass.

21:36

There are some areas that are a little bit less

21:38

brighter than the other areas, although predominantly

21:41

the mass is showing homogeneous, uh, signal intensity.

21:44

And here's the normal appearing,

21:47

uh, uterus reading into the cervix.

21:48

Here is the SAG fat-saturated T2-weighted image

21:51

again, showing nicely the outline of the uterus.

21:54

There is some free fluid, but here is the primary

21:57

lesion, multiloculated, um, So again, as you all

22:01

know from a differential perspective, um, when you're

22:03

looking at pelvic masses, ovarian masses, the, it's

22:08

the, the four sort of buckets we try and put them for

22:11

assessment in terms of differential is, is it unilocular?

22:14

Is it multilocular?

22:16

Is it a mixed solid and cystic lesion, or is it a predominantly solid lesion?

22:23

And so, this would fall into the multilocular category.

22:25

And, you know, just statistically, the commonest lesions

22:28

typically in a female pelvis are epithelial lesions.

22:31

So, epithelial neoplasms arising from the ovary.

22:35

So, again, here's a coronal fat-saturated T2, nicely showing

22:38

the multiloculated nature of the lesion. We don't

22:42

see a discrete solid nodular component on the T2.

22:46

This is a post-gadolinium enhanced fat-saturated image.

22:49

Again, the septae are enhancing, but we don't

22:53

see any distinct nodule within the lesion or in the wall of the lesion.

22:59

Here is the coronal again showing the same

23:07

finding, where you can see the septations are

23:10

predominantly peripheral and enhancing.

23:13

And here is a sagittal delayed image.

23:23

I'm not sure what this probably was, like a proton density

23:26

type of image, but... So here's, in summary, the appearance of the lesion,

23:31

which, so far, we have ascribed her pain to a pelvic lesion

23:36

that is likely arising from the ovary.

23:41

And in terms of differential, we have put this lesion

23:44

from a morphologic perspective into a multilocular

23:48

cystic lesion, likely arising from the right ovary.

23:52

And so, you know, the common etiology in that

23:55

instance is, as I said, you have to think about

23:59

epithelial lesions, typically a borderline or a

24:02

benign epithelial lesion arising from the right ovary.

24:08

If it was malignant, you would expect to see

24:10

more nodularity with early enhancement, um,

24:13

which is not seen in this case.

24:16

Now, it's interesting, if you look at the coronal,

24:18

CT images of the same patient, I just want to show you

24:22

these images one more time because that gives you a

24:25

clue as to the etiology of this specific entity.

24:30

So take a couple of seconds

24:32

to look at these coronal images.

24:36

And having seen that, what is the most

24:39

likely diagnosis in this particular case?

24:42

Is it a primary ovarian epithelial neoplasm?

24:45

Is it a large pelvic nerve sheath

24:47

tumor arising very close to the ovary?

24:50

Is it an ovarian metastasis with a GI

24:52

primary, or is it an ovarian germ cell neoplasm?

24:58

So it looks like, um, you know, there is a sort

25:02

of an equal distribution, um, uh, of the bulk, the

25:05

majority answered A, which is a primary ovarian

25:08

epithelial neoplasm, or D, ovarian germ cell neoplasm.

25:12

And then a few of you selected one each.

25:16

It's a pelvic nerve sheath tumor and ovarian metastasis.

25:19

Now, it's not an ovarian germ cell

25:21

because we don't see any fat, neither.

25:24

I showed you only the fat-saturated images on the

25:26

MR, but on the CT, there clearly is no fat density

25:30

seen, so that's going to be extremely unlikely.

25:32

So that can be excluded very safely.

25:35

The primary ovarian epithelial neoplasm still remains high

25:37

on the cards, but the reason I'm showing you this

25:40

case is, uh, you know, you have to be very careful.

25:43

You pay attention to the GI tract when you're

25:46

looking at ovarian lesions.

25:50

This was an ovarian metastasis of the GI primary.

25:53

So, where is the primary?

25:54

So, if you look at the coronal images again, uh, again, there

25:58

is oral contrast here, and you can see right here, there is

26:01

a fluid-filled distended appendix with some calcification.

26:05

And this was a, um, a mucinous adenocarcinoma

26:09

arising in the appendix with ovarian metastases.

26:12

So, you know, keep in mind, uh, this is

26:15

one, um, very important take-home point I

26:18

would like you to, uh, uh, to keep in mind.

26:20

So, uh, this was the finding on the scan and

26:24

here is a PATH report, uh, when they went in.

26:27

Uh, she had a right, uh, salpingo-oophorectomy,

26:30

which showed secondary involvement.

26:31

by a low-grade appendiceal neoplasm, and the

26:34

appendix did have a mucinous adenocarcinoma

26:38

with perforation and mucin extravasation.

26:40

The left ovary was fine, only had surface deposits.

26:43

So why am I showing you this case?

26:45

I'm showing you this case because this is a paper

26:47

from the PATH literature written by one of our

26:49

pathologists, and the important point here to take

26:52

home is that the appendiceal mucinous neoplasms have

26:56

a propensity to spread to the peritoneum and ovaries.

27:00

And, and the, the reason you need to understand

27:03

that is because it doesn't, um, there can be a

27:07

disconnect between the size of the appendiceal

27:09

lesion and the size of the ovarian metastasis.

27:12

And so you can have a relatively, you know, benign

27:15

fluid-filled distended appendix as was seen in this

27:18

case, but have a large metastatic deposit in the ovary.

27:22

And why is it important to make that distinction?

27:26

When they go in and do cytoreduction, there is a slight

27:29

varying point of view in terms of surgical approach and

27:33

post-surgical or neoadjuvant therapy if

27:36

a GYN oncologist is dealing with it or a

27:38

GI oncologist is dealing with the patient.

27:42

So let me show you two other

27:43

examples, a couple of other examples.

27:45

Here is a patient who has a fluid-filled distended appendix.

27:48

Do not ever discount that.

27:50

This patient also has a little bit of

27:51

peripheral calcification, and this also was

27:53

a mucinous adenocarcinoma of the appendix.

27:56

Here is a different patient which

27:58

this patient was called appendicitis.

28:00

In the emergency room.

28:02

And again, if you look closely, there is a, um,

28:05

fluid-filled distended appendix, and this was

28:07

actually perforated, uh, uh, uh, tumor with, with

28:11

mucin surrounding the cancer mimicking appendicitis.

28:15

They went in assuming it was appendicitis and found

28:18

cancer and then had to do a staged, uh, a staged

28:22

right colectomy at a later time point with, uh, you

28:26

know, with debulking, uh, of the mucinous deposits.

28:30

And here is another example.

28:31

This patient was thought to have a right ovarian lesion.

28:34

So here is an ovary on the ultrasound.

28:37

You can see there is a lesion in

28:38

very close proximity to the ovary.

28:40

And this is what was measured as a complex ovarian lesion,

28:44

or right adnexal mass arising from the ovary.

28:46

On CT, you can see it's a fluid-filled distended lumen

28:50

of the appendix with calcifications at the periphery.

28:52

So it can dip down fairly low on the

28:55

right side and mimic an ovarian neoplasm.

28:59

So the take-home points are: remember

29:00

ovarian metastases can and do occur.

29:04

They can be predominantly cystic.

29:05

They can be multiloculated cystic.

29:08

Or they can be solid and cystic masses.

29:11

The low-grade appendiceal mucinous neoplasms can spread

29:14

to the peritoneum and the peritonea, even though the

29:18

primary tumor does not look sinister or obviously invasive.

29:22

So this is very important to keep in

29:23

mind is there can be a disconnect.

29:25

So don't ever, ever discount the fluid-filled appendix.

29:28

In fact, you know, nowadays, whenever we see an

29:31

ovarian lesion, the first thing we do is look

29:33

at the appendix and make sure there is nothing

29:35

going on there or look at the rest of the bowel

29:37

and make sure there's nothing going on there.

29:39

So, so that's sort of the take-home message here.

29:43

All right, moving on to the next case, we have a 19

29:46

year-old, um, uh, young male patient from Chile who

29:51

was referred for abdominal pain and microhematuria.

29:55

The patient doesn't have any history of any surgery

29:57

in the past or any other medical condition.

30:00

You know, the mother says that he goes to school and then

30:03

comes back in pain and, you know, she took him to the

30:08

emergency room in Chile and they found microhematuria and

30:11

he has been worked up, and no one knew what was going on.

30:16

And so the patient had a CT,

30:17

which was a hematuria protocol CT.

30:19

So let me show you the non-contrast run first.

30:22

Obviously, in this case,

30:25

but this is sort of the early phase of enhancement.

30:28

And as we go down, you can see the kidneys

30:31

bilaterally show symmetric enhancement.

30:33

And, you know, if there were any obvious

30:36

stones, we would have seen it by now.

30:37

And we clearly don't see any hydro.

30:39

We don't see any renal masses.

30:41

We don't see any stones as we go down into the pelvis.

30:45

Here is the enhanced aorta.

30:52

So here is the right psoas muscle.

30:53

Here is the left psoas muscle.

30:55

I'm not going to have you, you know, spot the abnormality,

30:58

but it's right here in front of the right common iliac.

31:02

So keep an eye on that particular,

31:04

focal lesion, if you will.

31:08

And coming down into the pelvis, again, nothing obvious

31:11

to explain the patient's hematuria.

31:16

So let's look at the bone windows

31:19

sort of opacifying the collecting system

31:21

to see if there's any filling defects.

31:23

And again, we haven't seen any hydronephrosis.

31:25

I'm marching my way down.

31:26

You can see the ureters are bilaterally opacified, really.

31:30

And this was the lesion I was pointing out earlier,

31:34

not in any proximity to the ureter, not causing

31:39

any obstruction to the right, and there is a nice,

31:41

entry into the bladder.

31:46

Now, moving on to, this is slightly, the

31:50

soft tissue of the delayed scan, and again,

31:53

the same thing here, you can see the ureters

31:58

are nicely opacified, haven't seen any mass lesion,

32:00

but this is the area that we are looking for.

32:02

You know, talking about.

32:06

And so, between the I-minus and the enhanced images,

32:11

this particular lesion showed 35 Hounsfield unit change.

32:14

So it was an enhancing lesion.

32:17

So I pointed out the area of abnormality

32:19

as was seen on the axial scan.

32:21

And let's look on the coronal.

32:24

So again, we're looking at the early arterial and

32:26

sort of the, uh, you know, slightly delayed,

32:29

uh, if you will, the nephrographic phase images.

32:33

And so as we stroll our way, you can

32:35

see the vessels are nicely enhanced.

32:37

And this is the area of concern

32:39

you can see between here and.

32:41

Moving on.

32:41

It's just showing sort of brisk enhancement

32:46

and nothing else.

32:48

So, you know, young patient with, this

32:51

is not really retroperitoneal, a little

32:52

bit lower than what you would expect.

32:54

But one thing you always think about is, you know, am

32:56

I missing something in terms of looking at the testis?

33:01

So an ultrasound was performed and this is the

33:04

ultrasound image of that particular lesion itself.

33:07

So you can see it's hypoechoic, well-demarcated.

33:10

Um, it measures about six centimeters in long axis.

33:14

And on the Doppler, it does show some flow,

33:16

although it's not markedly hypervascular.

33:19

So it's not a vascular, um, vascular structure.

33:22

Again, here you can see there is some

33:25

increased flow seen in parts of the

33:27

lesion, but not really a vascular structure.

33:32

And then I'm going to show you a clip of the

33:37

testes bilaterally, you're looking at the right

33:39

and the left testes, and as we scroll through

33:44

this, you can see that the testes are normal.

33:47

We don't see any local masses within the testes

33:51

because, you know, one in especially in the second

33:54

and third decades, you think about intra-testicular

33:57

lesions with retroperitoneal, um, masses.

33:59

But in this case, the testes are absolutely normal.

34:04

And so subsequently, a PET CT was

34:06

also done just to kind of assess.

34:08

And, uh, you can see that there is some moderate activity,

34:11

but really it doesn't show a lot of, uh, uptake as you

34:15

would expect in something that was floridly FDG avid.

34:20

So again, a 19-year-old patient complaining

34:22

of microhematuria and abdominal pain.

34:25

All you see is a solitary lesion, which is well demarcated,

34:29

uh, in the low retroperitoneum or in the common iliac

34:31

region on the right side, appears to show brisk enhancement,

34:35

change about 35 units in terms of Hounsfield units.

34:38

Uh, the testes bilaterally are unremarkable.

34:42

And so that's, this is sort of in a nutshell, what

34:44

the lesion appears like in terms of enhancement.

34:47

And this is what it looks like on the, and

34:50

this finding, as we already discussed, there is

34:52

no splenomegaly or any other adenopathy seen.

34:55

And so the question is, what is your most likely diagnosis?

34:59

Are we dealing with an extra adrenal pheochromocytoma, a

35:02

benign neurogenic tumor, metastatic adenopathy, infectious

35:07

or inflammatory adenopathy, or neurogenic lesion?

35:12

Again, the patient is 19 years of age.

35:15

Uh, as I said, the testes were negative

35:18

bilaterally, doesn't have any other symptoms

35:24

except abdominal pain.

35:29

Okay.

35:29

So, um, uh, there is sort of a tie between

35:32

a pheochromocytoma and a neurogenic tumor.

35:35

A few have called it a neurogenic lesion and

35:37

the, uh, the three and four were not selected.

35:39

And clearly it's not metastatic because

35:41

we don't see anything in the testes now.

35:43

Could it be some other primary?

35:44

It's possible, but we don't see any other.

35:47

Extradrenal pheo, which typically happens in

35:50

the organ of Zuckerkandl in close proximity

35:52

to the inferior mesenteric artery and vessels.

35:55

The patient is not symptomatic.

35:57

Now that doesn't guarantee that it's not a.

36:00

It cannot be an extra adrenal pheo if the patient has

36:02

any kind of congenital predisposition, which again,

36:05

there is no syndromic possibility it could be a benign

36:09

neurogenic tumor. That seems like the most likely

36:13

possibility and they can briskly enhance and you

36:16

know, they can be benign. But this was an inflammatory

36:19

adenopathy and this patient had Castleman's disease.

36:22

So this is the other sort of entity

36:24

I want to make you aware of.

36:26

It's not as uncommon, you know,

36:27

we have seen a fair number of cases.

36:30

And so the classic path feature is hypervascular

36:32

lymph nodes with hyalinization of vessels,

36:34

which leads to the brisk enhancement we see.

36:37

And the reason why it's, um, you know,

36:40

it's a little bit near and dear because Dr.

36:42

Kesselman was at MGH, um, I was a

36:46

pathologist here in our hospital.

36:49

And so, you know, it can be uni or multicentric, but

36:52

the key features on, on imaging are you see nodal

36:57

lesions that show homogeneous brisk or intense enhancement.

37:01

There are three distinct patterns.

37:02

The most common is you see a solitary non-invasive well

37:05

circumscribed mass, as was seen in this particular patient.

37:09

The second is a dominant infiltrative mass.

37:12

So it kind of looks like an ill-defined well

37:14

lesion, but does show brisk enhancement.

37:16

And the last type is the matted multiple lymph nodes,

37:19

which is the least common of the three features.

37:22

So just to show you some additional

37:23

examples, this is another patient here.

37:26

You can see there is a large, uh, nodal

37:28

mass in the left side, fairly bright on

37:31

T2, uh, showing, um, a brisk enhancement.

37:34

And this was biopsied to be Castleman's.

37:37

And here is an example of the multicentric nodal

37:40

lesions, where in this particular patient, you're

37:42

seeing multiple nodal lesions in the right inguinal and

37:45

right pelvic region that are showing brisk enhancement.

37:48

So when you have hypervascular nodes, especially

37:51

if they are solid, I mean, solid and, and, um, and

37:55

single, consider Castleman's in the differential.

37:58

It's not that rare an entity.

38:00

And, you know, again, from an imaging

38:02

perspective, you can guide, uh, the, um, uh,

38:06

the, uh, the diagnosis towards that direction.

38:09

Of course, you need a biopsy to, to, you know, make the,

38:13

uh, to make the correct diagnosis, but at least you can

38:16

suggest it, especially if there is lack of any primary

38:19

and there is no evidence of metastatic adenopathy.

38:22

So hypervascular nodes, especially if it is

38:24

solitary, think about Castleman's disease.

38:29

Moving on to the next case, this

38:30

is a 59-year-old male patient.

38:33

who went to get his annual physical

38:35

exam done by the primary care physician.

38:39

The PCP, as part of the exam, does, you know,

38:43

a digital rectal exam and feels increased

38:45

firmness on the right side of the prostate.

38:49

The patient did have a recent PSA drawn, and

38:51

it was 2, so it wasn't really, you know,

38:53

increased, and the PSA density was fine as well.

38:58

So, has a prostate MRI done at an outside

39:02

institution where they comment on a 3.

39:04

2-centimeter pyrexial lesion, and he's referred to us

39:08

for a fusion-guided biopsy because the institution

39:11

where the MRI was done didn't have a fusion

39:13

apparatus, so they wanted us to do a fusion biopsy.

39:16

So I'm going to show you images from the MRI.

39:19

So let's start with the axial T2-weighted images first.

39:22

So as we scroll through, you can see the normal seminal

39:24

vesicles, a little bit of bladder outlet changes,

39:28

it's some thickening and increased trabeculation.

39:30

And as we come to the mid prostate, you can

39:33

see on the left side, there is the normal

39:35

peripheral zone and the transitional zone.

39:37

But on the right side, what you see is there is a lack

39:40

of the zonal differentiation that appears to be a

39:43

well-circumscribed lesion that is encompassing or

39:47

involving the transitional and the peripheral zones.

39:49

Okay.

39:51

And it extends right from the base

39:53

and goes all the way to the apex.

39:55

So that's what it looks like, just a magnified

39:58

view, and let's look at the coronal now.

40:00

So again, looking at the levator muscles as we come

40:03

down, you have the seminal vesicles coming down.

40:07

Here's the ejaculatory ducts coming in.

40:10

So again, the same thing here.

40:11

Look at the left side.

40:13

This is the normal central zone.

40:15

This is the bright signal from the, um,

40:18

uh, from the normal peripheral zone.

40:20

This likely is related to prostatitis on the left

40:22

side, but on the right side, you can see that there

40:24

is, you know, you're losing out on that, on that zonal

40:28

differentiation, and there is this area that goes all the

40:31

way from the base to the apex, like you saw on the axial.

40:35

And here is a magnified view of the, uh,

40:38

the coronal image as, as you can see it.

40:41

So clearly, there is an abnormal,

40:43

um, abnormality seen on the T2.

40:46

Now let's see the diffusion and the enhanced images.

40:48

So the top, you're looking at the high B value.

40:51

This is a B value of 2000, and this is an ADC image.

40:53

So as we scroll, you can see that the entire right

40:56

side is showing very bright signal on the high B value.

41:00

Marked signal loss on the ADC images.

41:04

Anteriorly, there is an area which shows much more

41:07

darker signal on the ADC and also brighter signal

41:10

on the B value of 2000 than the rest of the region.

41:14

So that's sort of what you see on

41:16

the diffusion again here.

41:18

And then as we look on the gadolinium-enhanced

41:20

images, this is the early phase of enhancement.

41:24

You can see that that whole area is enhancing early.

41:27

But this area that shows, um, heightened or

41:31

darkened ADC or more restricted

41:34

diffusion clearly shows a lack of enhancement

41:38

or there is rim enhancement in that location.

41:40

So the whole area is abnormal, but this area, which

41:43

is, uh, showing more restricted diffusion, and the rest

41:47

clearly shows, um, lack of enhancement or there is

41:50

peripheral sort of rim-like enhancement in that location.

41:53

So that is sort of the, uh, in a

41:55

nutshell, the, uh, the finding.

41:57

So the question is, what is your most likely diagnosis?

42:00

And here, these are your four options.

42:03

Uh, diffuse high-grade Gleason grade cancer, as was

42:05

called on the outside; they call it a Pyrex 5 lesion.

42:09

Is it BPH with normal asymmetric

42:11

peripheral zone due to prostatitis?

42:13

Is this a patient with granulomatous prostatitis

42:16

or are these post-biopsy changes on the right?

42:23

So remember, the PSA was 2.1,

42:25

the PSA density was not abnormal, but the PCP

42:32

clearly felt something rock-hard on the right side

42:36

on the digital rectal exam.

42:41

So yes, I think 100 percent, you got it correct.

42:44

The patient does have granulomatous prostatitis.

42:46

The patient had a history of high-grade, um, uh, superficial

42:50

bladder cancer for which he was treated with BCG.

42:54

I didn't give you this history, but

42:55

you know, you guys didn't need it.

42:57

And this patient has a case of granulomatous prostatitis.

43:01

And on the biopsy, they found dense granulomatous

43:04

inflammation with scattered microabscesses, which was

43:07

consistent with the diagnosis of granulomatous prostatitis.

43:10

So it can mimic cancer.

43:12

That's why we have to be aware of this entity.

43:14

And, you know, it's, it's a prior BCG therapy that is typically

43:19

the clinical scenario in which we

43:21

see this particular, uh, finding.

43:23

It's not very common in those patients,

43:26

but the point is, we don't scan everybody

43:29

that gets BCG therapy with a prostate MR.

43:31

Perhaps if we do, we will see more

43:33

cases of, uh, granulomatous prostatitis.

43:37

Um, so the debate is, is it an ongoing active

43:39

infection or is it hypersensitivity, and the presence

43:42

of granulomas and, and lack of organisms that can

43:46

be cultured from these biopsies, um,

43:50

suggest that it's likely a hypersensitivity reaction.

43:53

Um, slightly higher percentage in those patients where you

43:58

see the findings on those coming for prostate

43:01

MR for prostate cancer and they have the relevant history.

44:05

Um, and, you know, the, the, um, recommendation

44:10

is, uh, if the patient does get, um, obstructive

44:14

symptoms after this therapy, is, you

44:16

know, think about gynecomastia, uh, prostatitis,

44:18

and you can do an MR and, and, and prove it.

44:22

So the take-home message here, it can mimic

44:23

clinically significant cancer, can, it

44:25

can sometimes cause elevation of the PSA.

44:28

In about half the cases, it can; in

44:30

this patient, there was no elevation.

44:32

The clue is, you know, unlike prostate cancer,

44:34

which enhances homogeneously, uh, typically these

44:38

patients show peripheral rim-like enhancement.

44:40

Now this particular sign is not very

44:42

sensitive, but it is very specific.

44:43

So when you see this, it's very likely that this is,

44:46

that it is granulomatous inflammation and not cancer.

44:50

So this is typically what cancer enhances like.

44:52

This is a Gleason 8 tumor in the left peripheral zone.

44:54

You can see it's homogeneously enhancing.

44:57

And in this particular case where

44:59

this patient had BCG therapy,

45:01

you can see there is an area on the right side on

45:04

the T2 showing marked restricted diffusion, and on

45:07

the DCE showing peripheral rim-like enhancement.

45:10

There's also a smaller area on the left, same

45:12

thing showing peripheral rim-like enhancement.

45:14

So if you see that, think about granulomatous prostatitis.

45:18

And suggest that, uh, instead of a, you know, regular,

45:21

um, run-of-the-mill, uh, high-grade prostate cancer.

45:26

Moving on to the next case, uh, this probably will be the

45:28

last case, um, uh, it's a 50-year-old male patient being

45:32

treated for presumed renal infection with antibiotics.

45:36

Uh, and shows very little improvement of symptoms,

45:39

uh, continues to have vague abdominal pain,

45:42

weight loss, and occasional low-grade fever.

45:45

So remember, he, he is on antibiotics and,

45:48

you know, has been, uh, written off as

45:51

somebody having recurrent bouts of UTI.

45:54

And what he says is despite taking the antibiotics,

45:57

I'm not seeing any improvement in my condition.

45:59

And so a contrast in studies performed, so you can

46:02

see this is the axial CT images as we scroll through.

46:05

You can see on the axial images that there are

46:07

these peripheral low-density areas bilaterally,

46:11

cortical-based extending into the renal site,

46:13

into the medullary portion, not into the sinus.

46:17

It doesn't look like there is a lot of perinephric

46:19

There's some perinephric stranding, but not a lot

46:21

of perinephric stranding. But they are multiple bilateral

46:26

and not causing any hydronephrosis and not leading to

46:30

any, um, you know, any mass-like features, if you will.

46:35

So, and let's, let's look on the coronal again, better

46:38

appreciated on the coronal low-density areas, bilaterally,

46:42

uh, cortically-based extending into the med lab, but not

46:45

really into the renal sinus, no obstructive symptoms, uh,

46:48

no other adenopathy in the retroperitoneum as we saw, and

46:51

none of the other organs show any kind of visceral changes.

46:54

So, the question is, what is your diagnosis?

46:57

Is it multiple renal abscesses, IgG4 disease, is

47:01

it renal tuberculosis or is this renal lymphoma?

47:06

Again, none of the other organ systems

47:08

are involved in this particular patient,

47:12

you know, his chest x-ray was normal,

47:15

didn't show any changes in the chest x-ray.

47:18

Um, all he has is these symptoms and has been taking

47:21

antibiotics for quite some time with no improvement.

47:27

Perfect.

47:28

100 percent of you got it right.

47:29

This is IgG4 disease.

47:31

Um, so again, it's, you know, it is sort of a, not

47:36

a new, but it's a multi-system, uh, inflammatory

47:40

disorder that can lead to mass-forming lesions.

47:43

Thank you for joining us.

47:43

It's marked by IgG4-positive plasma cells in the affected

47:47

organs, typically seen in the lacrimal glands, but

47:51

you can see it in the abdomen and pelvis, the pancreas,

47:54

kidneys, and the retroperitoneum that can be affected.

47:57

The kidneys, uh, in terms of a GU infection, are a

48:00

representative organ and collectively, when you see

48:04

the lesions referred to as IgG4-related kidney disease.

48:08

And so they can present with unexplained renal

48:10

dysfunction and imaging abnormalities as we saw here.

48:13

These patients typically have elevated serum

48:16

IgG4 levels, although about, you know, one

48:20

fourth can have normal serum IgG4 levels.

48:22

So that's something important to keep in mind.

48:25

And the, the real, uh, sort of, um, therapeutic, uh,

48:29

intervention in terms of giving corticosteroids and

48:32

there is a dramatic response that these patients show.

48:36

It's important to remember that the IgG4 spectrum

48:38

in the kidneys can have varying patterns.

48:41

So what we saw was bilateral, round, or wedge

48:44

shaped areas, predominantly cortical-based.

48:47

Now remember, lymphoma can do the same thing.

48:49

So that's one common differential

48:50

that you have to keep in mind.

48:51

But that's the most common presenting feature for IgG4.

48:55

You can have diffuse patchy involvement.

48:58

You can have a rim of soft tissue surrounding

49:00

the kidney as you see in the pancreas.

49:02

And just to show an example quickly,

49:04

this is a non-contrast study.

49:06

You see that there is a lot of soft tissue or low

49:08

density that surrounds the retroperitoneum, as

49:11

well as the kidneys, um, mainly on the right side.

49:13

And this was biopsy-proven IgG4.

49:16

Again, better seen on the coronal where you

49:18

can see the soft tissue line that surrounds.

49:21

The kidney.

49:22

There is also low-density areas within the

49:23

kidney itself, but there is a lot of soft

49:26

tissue surrounding the aorta.

49:29

There is a different patient where

49:32

there is perinephric soft tissue.

49:33

In this case, there is calcification.

49:36

So that can also be seen with IgG4.

49:38

The differential here would be amyloid.

49:40

That can sometimes mimic, you know, this particular

49:44

finding, but this was biopsy-proven IgG4. You can

49:47

have bilateral nodules in the renal sinus. You can

49:50

have diffuse thickening of the renal pelvis and

49:52

I can just show you a 3D MIP of a case here. The

49:56

patient has diffuse circumferential thickening of

49:00

the renal pelvis that was proven to be IgG4 again.

50:03

It's very difficult to preemptively make the diagnosis,

50:07

you need to get a biopsy, but suffice it to say that

50:09

it can mimic an invasive renal sinus tumor.

50:15

And then finally, you can get a solitary mass-like lesion.

50:18

And that's what is seen in this case where it

50:21

looks like there is a lesion, non-contrast and

50:23

contrast-enhanced, which is infiltrating into

50:25

the adjacent liver parenchyma.

50:29

And this turned out to be IgG4.

50:33

And so that's, that's sort of the coronal image

50:36

showing, coronal and sagittal images showing depiction

50:38

of the involvement of the liver.

50:42

So the takeaway here is that IgG4 can

50:44

mimic both neoplasms and infection.

50:47

You know, if the patient is not responding to

50:49

therapy, if the symptoms persist, especially if

50:51

the lesions are multifocal and affect the kidneys

50:55

bilaterally, you know, then think about IgG4.

51:00

So I think in the interest of time, I'm going to stop here.

51:02

If there are any questions about the cases that

51:04

we have seen thus far, I'll be happy to answer.

51:09

I am not seeing any questions pop up so far, Dr.

51:11

Harrison Ghani.

51:16

So I guess everything was very clear and you

51:18

know, you guys got most of the cases right?

51:20

So it sounds like you're a great teacher

51:23

and we—Oh, here's one that just popped up.

51:26

For IgG4, is there always antibiotic administration?

51:30

And the answer is no.

51:31

But remember, these patients don't, uh, typically

51:34

present with classical findings.

51:37

So they are assumed to have either a tumor or infection.

51:41

And so not infrequently, they will be put

51:44

on, you know, antibiotic therapy, thinking

51:46

that these are abscesses.

51:48

And when they don't respond to therapy, that's

51:50

when you need to start thinking of IgG4.

51:52

So it's not always, but frequently, I would say.

51:57

Thank you.

51:57

Thanks again.

51:57

Thank you.