0:02

Hello and welcome to Noon Conferences hosted by MRI online. 2 00:00:03,360 --> 00:00:05,610

0:05

In response to the changes happening around

0:07

the world and the shutting down of in-person

0:08

events, we have decided to provide free daily

0:10

noon conferences to all radiologists worldwide.

0:12

Today we're joined by Dr. Sherry Wang.

0:14

She's an assistant professor at

0:15

abdominal imaging at the University of Utah.

0:18

Previously, she did her body imaging fellowship at

0:20

the University of Washington in Seattle, and her

0:22

radiology residency in Australia. Reminded there will

0:24

be time at the end of this hour for a Q and A session.

0:27

Please use the Q and A feature to ask all

0:28

of your questions, and we'll get to as

0:29

many as we can before our time is up.

0:31

That being said, thank you so much

0:33

for joining us today, Dr. Wang.

0:34

I'll let you take it from here.

0:37

So, hi everyone, I'm Sherry Wang, and, um, I'm currently

0:40

an assistant professor at the University of Utah

0:43

doing abdominal imaging, and today we're gonna be

0:46

talking about imaging of gastrointestinal bleeding.

0:50

For full disclosure, I chose this topic because

0:53

this was something that was very confusing

0:56

and challenging as a radiology resident.

0:59

And honestly, honestly, these were

1:01

not my favorite studies to read.

1:04

I hope this lecture can help those who find this topic

1:07

challenging and hopefully embrace—I won't go as far

1:11

as to say love—um, reading these particular studies.

1:16

So, um, my only disclosure is that I

1:18

received book royalties from Elsevier.

1:22

Before I start, I would like to, um, give

1:24

acknowledgements to Dr. Araf Ali from the

1:27

University of Cincinnati, as well as Dr.

1:30

Jonathan Res from the University of New Mexico.

1:36

So here are our objectives for today.

1:39

So we wanna understand how gastrointestinal

1:42

bleeding can be imaged using different modalities.

1:46

Wanna explain the CT protocols used in the cases

1:51

for, um, suspected gastrointestinal bleeding.

1:55

Illustrate the main radiological signs to identify

1:58

the presence of bleeding, its source, and its cause.

2:03

And lastly, highlight the major pitfalls of CT

2:06

in the evaluation of gastrointestinal bleeding.

2:12

So GI bleeding is a serious clinical problem.

2:16

In fact, it is a leading GI disease-

2:18

related cause of hospitalization in the US.

2:23

GI bleeding can be divided up by

2:25

where the location of the bleed is.

2:28

This is actually very, very important because the

2:30

location would change the management and associated

2:34

prognosis. For location of GI bleed, it's broken up into

2:40

upper GI bleed, lower GI bleed, and small bowel bleed.

2:46

In the management of GI bleeding,

2:48

there is a multidisciplinary approach

2:50

needed, and radiology is very important.

2:55

Um, as part of this multidisciplinary approach,

2:59

the evaluation of location of bleeding and etiology

3:03

is important because we want to help the, um,

3:05

clinicians find the best therapeutic approach.

3:10

Non-invasive imaging techniques, especially CT, are

3:15

now heavily utilized in the evaluation of GI bleeding.

3:21

So upper GI bleed is defined as

3:24

bleeding proximal to the ligament of Treitz.

3:28

Upper GI bleed occurs more frequently compared

3:31

to lower GI bleed with an incidence of 100

3:35

to 100 cases per hundreds annually.

3:41

Upper GI bleed also accounts for over

3:44

300,000 hospitalizations each year with

3:49

a mortality ranging between 3.5 to 10%.

3:55

Patients can present with hematemesis. They can be

3:59

coffee ground or frank blood, as well as melena.

4:04

In the clinical setting, nasogastric lavage

4:08

can be performed to assess for blood in the stomach.

4:12

However, when this is negative, this

4:15

does not exclude upper GI bleed.

4:18

If the source is distal to the pylorus.

4:24

Lower GI bleed is defined as

4:26

bleeding from the colon or rectum.

4:30

The incidence of lower GI bleed is less than that

4:34

of upper GI bleed and ranges between 20.5 to 27

4:40

cases per 100,000 persons annually.

4:44

The mortality of lower GI bleed is

4:47

also lower than that of upper GI bleed.

4:50

It ranges between 2 to 4%.

4:53

This difference is due to the limiting nature of lower

4:57

GI bleed, and up to 80 to 85% of cases will spontaneously

5:03

resolve, and only supportive measures are needed.

5:07

The clinical symptoms that the patient may

5:10

experience for lower, um, GI bleed are hematochezia

5:13

and melena if the bleeding source

5:17

is from the ascending colon/cecum.

5:24

So, small bowel bleeding is another category, and

5:27

it's defined as bleeding that is not upper or lower

5:31

GI.

5:32

I know it sounds very self-explanatory, and

5:35

this term is usually given, um, by the clinician

5:39

when the upper and lower GI tracts have been

5:41

assessed and they couldn't find a bleeding source.

5:45

And this can be a huge clinical dilemma.

5:51

So here's some terminology.

5:53

Um, overt means, um, visible.

5:56

So when the clinician writes this, it means the

5:58

patient has symptoms that they can see blood,

6:02

such as hematemesis, hematochezia, and melena.

6:07

Occult bleeding is bleeding that cannot be visualized.

6:12

But there are symptoms and signs that

6:14

the patient can have that show that

6:16

they are indeed bleeding from somewhere,

6:19

um, such as a positive fecal test or anemia.

6:25

This is actually a table showing some of the common

6:28

etiologies, um, for causes of upper and lower GI bleed.

6:34

So for upper GI bleed, we have

6:36

things like peptic ulcer disease.

6:38

This could be either duodenal or gastric in

6:41

location, esophageal lesions due to reflux,

6:46

such as esophagitis or esophageal ulcers.

6:50

Portal hypertension can also be a potential

6:53

cause for upper GI bleed because their,

6:56

um, portal hypertension patients will often

7:00

have paraesophageal and gastric varices.

7:04

Tumors are something to be

7:06

aware of in the upper GI tract.

7:08

Um, adenocarcinomas and gastrointestinal

7:11

stromal tumors can also be a source of bleeding.

7:16

Other causes in, um, the upper GI system include

7:20

aortoenteric fistula, Dieulafoy lesions, and hemobilia.

7:26

For lower GI bleed, tumors are kind of top at our

7:30

list, so things like colonic adenocarcinoma is

7:34

probably one of the most common, but we must

7:37

not forget inflammatory infectious causes such as

7:41

inflammatory bowel disease and colonic diverticulitis.

7:45

I think vasculitis can be both

7:47

inflammatory and vascular.

7:50

Um, and in the vascular box we also have, um,

7:54

angiodysplasia, ischemic colitis, and hemorrhoids.

7:59

Other causes include colonic diverticulosis.

8:03

This is important because you don't need the

8:06

diverticulitis in order to cause bleeding.

8:09

And, um, endometriosis is another

8:11

potential cause for lower GI bleed.

8:16

Here I'm going to go through the American

8:19

College of Radiology's appropriateness

8:21

guidelines for upper and lower GI bleeds.

8:25

I find this document and these resources very, very

8:29

helpful for myself, for the radiology resident as well

8:33

as for our referring clinicians because they can always

8:37

look up what is the best, um, imaging technique to

8:41

employ, um, depending on their clinical situation.

8:47

So the American College of Radiology has adopted these

8:50

clinical practice guidelines for the imaging in the

8:54

management of gastrointestinal bleeding, and for upper

8:58

GI bleed, endoscopy should be performed first in all

9:02

instances of non-variceal upper GI bleed, unless there's

9:07

some kind of contraindication. Endoscopic diagnosis,

9:12

um, endoscopic diagnosis is successful, um,

9:17

in identifying the sources of hemorrhage

9:20

in up to 95% of cases, and simultaneously

9:25

facilitates therapeutic hemostasis.

9:30

In the literature, there is a variability of when is

9:33

the best timing for endoscopy to be performed, but the

9:38

literature does support that there are superior outcomes

9:42

in terms of decreasing the length of hospitalization,

9:45

re-bleeding rates, transfusion requirements,

9:49

and surgical interventions when early endoscopy

9:53

is performed, that is within 24 hours of

9:57

presentation after initial hemodynamic resuscitation.

10:03

According to the ACR appropriateness guidelines,

10:07

imaging should be used when there are

10:09

contraindications to endoscopy. So contraindications

10:14

include trauma, postoperative setting, or when

10:19

endoscopy did not find the source of bleeding.

10:23

Conventional angiography has the

10:26

highest appropriateness rating.

10:29

However, CT angiography is a

10:31

comparable non-invasive alternative.

10:37

CT enterography is the next best option

10:40

for those patients with negative endoscopy.

10:44

A nuclear medicine scan, which is a tagged red

10:47

blood cell scan, may be appropriate when there

10:50

is slow bleeding, negative endoscopy, or no

10:54

clear source of bleeding could be detected.

10:59

Now moving on to the ACR appropriateness

11:02

guidelines for lower GI bleed.

11:06

The management of a lower GI bleed is largely

11:09

dependent on the patient's hemodynamic

11:12

status after initial resuscitation.

11:15

So as you can imagine, the biggest limitation for

11:19

colonoscopy is the need for bowel preparation.

11:22

Due to this, the ACR guidelines rate colonoscopy

11:26

as an appropriate initial management tool

11:29

only for hemodynamically stable patients who are able

11:34

to undergo sufficient bowel preparation.

11:39

Imaging-wise,

11:41

tagged red blood cell scans or CT angiography

11:44

of the abdomen and pelvis are comparable first-

11:47

line alternatives when colonoscopy cannot

11:50

be performed. Tagged red blood cell scans are

11:55

useful in the setting of a negative colonoscopy

11:58

and when the bleed is slow or intermittent.

12:02

This modality compared to the others has

12:05

the best sensitivity for slow bleeding.

12:09

Colonoscopy yields superior diagnosis and

12:12

hemostasis compared to conventional angiography.

12:17

So conventional angiography is usually reserved

12:21

for patients with severe gastrointestinal

12:23

bleeding and are hemodynamically unstable.

12:27

And this, um, modality is an alternative to surgery.

12:34

Um.

12:35

Conventional angiography is also appropriate

12:38

in patients with recurrent or persistent

12:41

bleeding after colonoscopy hemostasis.

12:46

It has been shown that there is superior diagnostic

12:49

yield as well as decrease in morbidity and mortality

12:54

when non-invasive imaging is performed prior to

12:58

colonoscopy, conventional angiography, or surgery.

13:02

So, um, CT really does play a role in,

13:07

um, optimizing patient management and care.

13:12

Surgical management is a definitive therapy

13:16

that is usually reserved for emergent cases

13:19

where the risk for exsanguination is high.

13:25

So this is a table showing what is the

13:28

estimated, um, detectable rates of bleeding

13:32

of the different imaging techniques.

13:35

And you can see for each modality there are

13:38

threshold rates of bleeding that is needed in

13:42

order for us to see it on that particular modality.

13:46

So nuclear medicine tagged red blood cell scan

13:50

needs an estimation rate of bleeding which

13:53

is greater than 0.2 milliliters per minute.

13:58

CT angiography requires a greater than 0.35

14:02

milliliters per minute bleeding rate to be detected.

14:07

And lastly, conventional angiography

14:10

requires a greater than 1 milliliter per

14:13

minute rate of bleeding to be detected.

14:17

As you can see, um, you need a quite fast, um,

14:23

bleed rate for conventional angiography.

14:26

But the advantage of conventional angiography is

14:29

that therapy can be performed at the same time.

14:34

Now we're going to move on to CT as a modality in

14:37

the investigation of gastrointestinal bleeding.

14:42

So, CT, as everybody knows, is

14:45

widely and increasingly utilized.

14:48

The reasons being it's universally

14:50

available and it's readily accessible.

14:53

The images can be rapidly acquired,

14:56

and it's actually very, very accurate.

14:59

There's a sensitivity of, um, 85.2%–100%.

15:05

Um, CT is not without advantages and disadvantages.

15:09

Um, for advantages, CT is able to localize

15:13

the source of arterial or venous GI bleed.

15:18

This is really important.

15:20

Because arterial bleeds can be

15:22

embolized and venous bleeds cannot.

15:26

Secondly, CT is able to diagnose the

15:29

underlying pathology that may be the cause

15:31

of bleeding to direct future management.

15:36

So you may not be able to see an active

15:38

bleed, but you may be able to see something

15:41

that may be the cause of chronic, slow, and

15:44

intermittent bleeding, such as a huge mass.

15:50

Thirdly, CT can diagnose causes of

15:53

bleeding not within the GI tract.

15:56

Um, this is very important when

15:59

the etiology is a vascular one.

16:02

And lastly, CT can delineate the underlying

16:06

vascular anatomy prior to embolization

16:09

and characterize any anatomical variants.

16:13

This is very helpful to our

16:15

interventional radiology colleagues.

16:18

The disadvantages of CT include decreased

16:22

sensitivity relative to radionuclide imaging,

16:27

as, um, you remember from the past slides.

16:30

For CT detection, the rates of bleeding need

16:33

to be faster compared to radionuclide imaging.

16:39

CT has a high radiation dose associated with it.

16:42

Um, CT, when utilizing CT for GI bleeds, um,

16:47

you always need to perform it

16:50

with all three phases, so that's essentially

16:54

multiple CTs and increased radiation dose.

17:00

There is a need for IV contrast and this

17:03

can be very difficult when the patient has,

17:06

um, poor or difficult IV access, allergies to

17:10

iodinated contrast, or poor renal function.

17:15

In those cases, um, a discussion should kind of be

17:18

had with the clinician to see how urgent and how

17:21

clinically relevant the study is, and, um, that's

17:26

a discussion you need to have with the clinician.

17:28

Lastly, false negative results if the

17:31

patient is not bleeding at the time of scan.

17:34

I think this is not a true disadvantage of

17:37

CT because like all the other modalities, the

17:40

patient needs to be bleeding at the time of scan.

17:43

Um, how you pick which modality you pick really

17:46

depends on the rate of bleeding at the time of scan.

17:54

So CT angiography of the abdomen and pelvis.

17:57

Like I said before, it's a multi-phase study.

18:01

You have the non-contrast, arterial, and

18:05

portal venous phase, and I'm

18:08

going to repeat this again and again.

18:11

Do not give positive oral contrast.

18:15

Um, this is how important, how important

18:18

I think this particular thing is.

18:19

Um, as a major pitfall when,

18:21

um, dealing with GI bleed CTs.

18:25

So my motto in life is do it right and do it once.

18:29

So it takes a lot of effort to get a patient

18:32

to a scan from scheduling, getting the patient

18:35

down, IV access, IV contrast, et cetera.

18:39

So we should get it right the first time.

18:42

Not only that, say for example if

18:45

you miss the non-contrast phase.

18:48

You can't really go back and scan the patient

18:50

again if the IV contrast has already been given.

18:55

Similarly, you can't just re-scan the patient if

18:58

you missed any of the timing because when the timing

19:01

is incorrect, it may lead to wrong interpretation.

19:05

And lastly, one cannot just reinject IV contrast

19:10

either as you already have contrast on board and

19:13

that'll just muddy the water and impair interpretation.

19:18

This is actually our CT protocol for a lower

19:21

GI bleed, and you can see we have non-contrast,

19:26

arterial phase, and portal venous phase.

19:31

No oral contrast.

19:34

Some institutions also have a coronal MIP

19:38

series, which is maximum intensity projection

19:41

for the arterial phase, and this can really

19:44

help intensify the appearance of contrast

19:46

extravasation. Dual-energy CT has become increasingly

19:52

employed in the evaluation of gastrointestinal bleeding.

19:57

The idea of dual-energy CT is that it uses

20:00

two different scanning voltages, one high,

20:04

typically 140 kVp, and one low, typically 80 kVp.

20:11

And because of the two different voltages, it

20:13

can delineate between different substances.

20:16

And this is useful because you can create an

20:18

iodine map from these images when IV contrast

20:22

has been administered.

20:25

And similar to the idea of a coronal MIP, this can help

20:29

intensify the appearance of contrast extravasation.

20:34

The other advantage of dual-energy scanning is that,

20:38

uh, virtual non-contrast can be created, and this

20:43

can help decrease the number of phases, um, that

20:46

we scan the patient and, um, save radiation dose.

20:52

The dual-energy technique can also utilize the

20:56

K-edge of iodine, and by doing this, we can make

21:00

iodine more conspicuous when evaluated with a low

21:04

kVp or keV, thus, again, intensifying the contrast

21:10

extravasation.

21:15

Small bowel bleeding is when endoscopy

21:18

and colonoscopy are both negative.

21:21

The patient has persistent or recurrent GI bleeding.

21:24

So it's presumed that the bleeding

21:27

has to be from the small bowel.

21:29

And my discussions with a lot of our clinicians is

21:33

this is a really big diagnostic dilemma for them.

21:38

Um, capsule endoscopy is the preferred technique,

21:43

but it only has a diagnostic yield of 32 to 76%.

21:49

And complete examination of the small

21:51

bowel is only achieved in 74% of patients.

21:56

And then in 1.9% of patients you have capsule

22:01

retention or surgical retrievals that are needed.

22:05

There are several contraindications

22:07

for capsule endoscopy.

22:09

They include pacemakers, dysphagia,

22:12

and suspected small bowel strictures.

22:15

So the last one you can,

22:17

it's kind of self-explanatory because if

22:19

you've got small bowel strictures, it's going

22:22

to stop the capsule from advancing further.

22:25

It can cause small bowel obstruction and

22:28

therefore you need surgical retrieval.

22:31

The other big downside of, um, capsule

22:34

endoscopy is actually the long turnaround time.

22:37

So you can imagine the capsule

22:39

going through the GI tract.

22:40

That's a lot of images to be reviewed, and

22:44

this makes it unsuitable for the evaluation

22:47

of acute severe small bowel bleeding.

22:54

CT enterography is similar to the CT angiography

22:58

that we spoke about previously in that it needs,

23:01

it's a multi-phase technique and you need all phases.

23:06

Neutral oral contrast agent is used.

23:09

This is the same neutral oral contrast agent we use

23:13

for the assessment of inflammatory bowel disease.

23:17

The idea is the same.

23:18

You want to distend the small bowel loops

23:21

to evaluate not just the extravasation of

23:25

contrast, but also the small bowel mucosa.

23:29

It doesn't have a great sensitivity.

23:32

It varies between 33 to 45%.

23:37

And the other, um, problem is given

23:41

the need for oral preparation.

23:43

This is usually reserved for patients with suspected

23:46

small bowel bleeding who are hemodynamically stable.

23:51

Nevertheless, it's a very important technique, not

23:55

just for the localization of an active bleed, but

23:59

also to assess for any underlying small bowel vascular

24:03

lesions, any masses, or even for inflammatory bowel

24:07

disease, as all of the above can cause bleeding.

24:15

This is our protocol for CT enterography.

24:19

And we, we delineated this from our usual CT

24:22

enterography by putting the three phases on.

24:25

Um, the reason being that the chances of

24:28

people wanting the ordering or protocol

24:31

in the wrong, um, study is decreased.

24:34

So here we have an arterial phase, an enteric

24:38

phase, which is 20 to 25 seconds delay, and a

24:43

delayed phase, which is 70 to 75 seconds delay,

24:48

which is kind of like a portal venous phase.

24:51

And for the oral contrast, it’s a neutral.

24:54

Contrast trade name is VoLumen, and we give a

24:58

total — well, we try to give a total of 1.35 liters.

25:02

I know that is a lot, and sometimes

25:05

the patient cannot tolerate it.

25:07

Um, but it should be encouraged to

25:09

help distend the small bowel loops.

25:15

Now we're gonna go through some imaging

25:17

features of, um, GI bleed on CT.

25:22

The arterial phase is typically the most useful in the

25:25

evaluation of active bleeding, but when you sequentially

25:30

compare all of the three phases, this actually

25:33

offers best, um, performance and highest sensitivity.

25:39

So the arterial phase is sensitive for

25:42

contrast in active and acute hemorrhage.

25:48

There are actually quite variable preferences

25:50

on how the contrast extravasates.

25:54

And what you are looking for is

25:56

high-density intraluminal contrast.

25:59

So this should be greater than 90 Hounsfield

26:02

units when you put your ROI on.

26:06

And linear extravasation can be very tricky,

26:10

because it can be confused with vessels.

26:13

So in those cases, you should look at the portal venous

26:17

phase to see the change in configuration.

26:20

Usually it looks very linear on arterial

26:23

phase, and then on the portal venous phase,

26:25

it looks more cloud-like and amorphous.

26:28

And if it does that, you can very

26:30

confidently say that this is active bleed.

26:37

Here is a case of active arterial bleeding.

26:40

This is a 77-year-old patient who presented

26:44

with decreased blood pressure and melena.

26:47

So we have CT angiogram in arterial

26:50

phase, axial and coronal reform.

26:53

Here we have a hyperdense clot adjacent

26:57

to a focus of active circular bleed.

27:02

This is a 45-year-old patient with a

27:06

gastric pull-through, performed for a

27:08

history of, um, esophageal carcinoma.

27:12

And this patient presented with hematemesis.

27:16

CT angiogram.

27:17

Axial image shows an area of active linear

27:22

extravasation in the stomach, and there is

27:26

pooling of contrast on the delayed phase.

27:29

So this is in keeping with active arterial bleed.

27:35

So the other two phases are also very, very

27:38

useful, and the venous phase, um, is the phase

27:42

you want to look for slow or delayed bleeding,

27:46

or bleeding from the portal venous system.

27:49

This is an important phase to characterize

27:52

bowel mucosal lesions or vascular malformations.

27:57

You may not be able to see an active bleed with

28:00

these entities because they're often chronic,

28:04

slow and intermittent, and usually below the

28:08

threshold for detection on non-invasive imaging.

28:14

Inflammatory bowel disease is a common

28:16

cause for gastrointestinal bleeding,

28:19

and CT enterography is useful for this.

28:23

So then what's the use of the non-contrast series then?

28:28

Well, the non-contrast series is particularly useful in

28:31

localizing hematoma, and blood products appear dense

28:37

and tend to layer dependently with a fluid-fluid level.

28:42

So unclotted blood is about 30 to 45 Hounsfield units.

28:48

Clotted, um, blood is more dense at 45 to 70 Hounsfield units.

28:56

The initial non-enhanced scan can also help delineate

29:02

hyperdense structures in the bowel, such as food,

29:06

surgical clips, retained contrast within diverticula.

29:12

And, um, it's important to, if you see something that is

29:15

very, very bright on the arterial phase, always go to the

29:18

non-contrast and see was it previously already there.

29:21

And this can help reduce the probability

29:25

of false positive misinterpretations.

29:31

Here we have a case, um, of a 54-year-old

29:34

patient who presented with GI bleeding

29:37

and decreased hematocrit. CT angiogram.

29:41

Um, axial image showed no contrast

29:46

extravasation.

29:48

However, on the portal venous phase,

29:51

you can see contrast extravasation and pooling.

29:55

And this is in keeping with

29:56

slow or delayed, um, bleeding.

30:00

So on the portal venous phase, you

30:02

want to look for any extra, um,

30:06

from accumulated blood that's pooling.

30:12

This.

30:13

I think this image really, um, accentuates

30:17

the power of the non-contrast study.

30:20

So here we can see a hyperdense,

30:23

um, focus within the lumen.

30:27

Um, and this is in keeping with clot.

30:30

So even if you are unable to see an active bleed

30:34

on the subsequent arterial and portal venous

30:37

phases, at least you can guide the clinician and

30:40

say, well, I see a lot of clot here, so this is

30:42

probably where the source of the bleeding is.

30:46

And the term sentinel clot is hematoma with the highest

30:52

attenuation seen closest to the site of bleeding.

30:59

As we said before, there are multiple

31:02

different extravasation appearances,

31:04

and we'll go through some cases now.

31:08

This is a 37-year-old patient with acute upper

31:12

GI bleed, and on the CT angiogram you can

31:17

see active linear extravasation of contrast

31:21

into the stomach on the arterial phase.

31:24

On the coronal image, um, in the delayed phase,

31:28

you can see there's a change in configuration,

31:31

so it went from very linear to a blob.

31:34

So this is in keeping with active arterial

31:37

bleed. On conventional angiography, a small

31:42

bleed can be seen at this location and

31:45

subsequently embolization was performed.

31:51

This case is of a 56-year-old

31:54

patient with a hematocrit drop.

31:57

The arterial axial CT demonstrates a linear

32:01

active bleed with a beautiful fluid-clot level,

32:07

so the more dense stuff is clot, and because

32:10

it's heavier, it drops down to the bottom.

32:12

And active bleeding was confirmed on

32:16

conventional angiography, also subsequently embolized.

32:24

This is a 61-year-old patient who came in

32:27

with GI bleed that had a history of total

32:30

pancreatectomy and biliary stent procedure.

32:35

So the initial CT angiogram was negative for

32:38

active bleed, but the conventional, um, angiography

32:42

demonstrated a pseudoaneurysm, um,

32:47

arising from a branch of the left hepatic artery.

32:52

There is likely a biliary fistula for the

32:54

blood to be able to track into the biliary

32:57

system and then subsequently into the GI

33:01

tract, um, by the second part of the duodenum.

33:05

And then in retrospect, perhaps there was a

33:08

small pseudoaneurysm at this location, but

33:12

everything is easier to see in retrospect.

33:14

Right.

33:17

This is a case of a 51-year-old patient with GI bleed.

33:22

Which was unable to be located on upper and lower scopes.

33:27

Post-contrast arterial phase axial CT

33:31

demonstrates, um, active extravasation.

33:34

And this one it looks very cloud-

33:36

like in the, um, hepatic flexure.

33:43

This is a 76-year-old patient

33:46

with acute on chronic bleed.

33:50

Post-contrast arterial phase CT

33:53

demonstrates active extravasation in

33:57

the rectum, and here they're very linear.

33:59

So you can see how you can really get fooled

34:02

by thinking these linear things may be, um,

34:05

vessels, but actually just the beginning of

34:08

the extravasation, and then you get to see them

34:10

better on the subsequent portal venous phase.

34:17

This is a 47-year-old with acute on chronic bleed.

34:22

So on the non-contrast study we see hyperdense

34:26

material within the mid small bowel lumen in

34:29

keeping with a clot. On the arterial phase,

34:34

we don't see any extravasation in the mid small bowel.

34:38

However, at this location there is active bleed

34:44

on the portal venous phase, in keeping with an

34:47

active bleed, which is either vascular or slow.

34:52

There's actually another focus of active bleed more

34:57

distal to the above-mentioned location in the distal

35:00

small bowel with active linear arterial bleeding.

35:05

So be cautious of satisfaction of search.

35:10

I know the bowel is very, very long, but, um,

35:15

sometimes you can find multiple locations of bleeding.

35:21

Now we'll go through some entities that

35:24

often cause chronic, slow, and intermittent

35:27

bleeding, which can be below the threshold

35:30

for detection on non-invasive imaging.

35:35

This is a 57-year-old patient with per rectum blood,

35:40

and the CT, um, angiography demonstrates a large

35:45

enhancing right anal/rectal mass, and

35:49

there were no areas of active bleed seen on CT.

35:56

This is a 54-year-old patient with

35:59

melena and abdominal pain.

36:02

So for this particular study, a dual

36:04

energy CT was performed for suspicion of a

36:08

small bowel, uh, mass, and an enhancing mass

36:13

was seen in the ileum on post-contrast axial CT.

36:20

The loops proximal to the lesion

36:22

are dilated, and the loops

36:26

distal to the lesion are collapsed.

36:29

So this lesion may be causing

36:31

mechanical small bowel obstruction.

36:34

And this was the iodine map that I was talking about.

36:37

So it kind of just shows where

36:38

the iodine kind of lights up.

36:40

And this mass was definitely better visualized on the

36:44

iodine-only images from the dual-energy CT examination.

36:49

This was in keeping with a small bowel carcinoid.

36:57

This was a 65-year-old patient with anemia.

37:01

So post-contrast CT axial images and sagittal

37:04

reformat demonstrate a mass in the rectum, which

37:09

is highly suspicious for rectal adenocarcinoma.

37:13

And this was an etiology for the patient's symptoms.

37:20

It can also be vascular causes.

37:23

Um, so this is a 73-year-old patient

37:26

with severe hematemesis and hypotension.

37:32

CT angiogram demonstrates a small pseudo-

37:35

aneurysm arising from a branch of the IMA artery.

37:42

This was also seen on the conventional

37:45

angiography and subsequently embolized.

37:49

This was deemed to be the source

37:51

of the patient's GI bleed.

37:57

This is a 57-year-old patient with Hepatitis C and

38:02

liver cirrhosis presenting with acute GI bleed.

38:08

CT angiogram demonstrates

38:09

large varices in the gastric wall.

38:13

No active bleed seen on CT.

38:17

The varices are much more prominent

38:19

on the portal venous phase.

38:21

These large gastric varices were the

38:24

source of the patient's GI bleed.

38:30

And lastly, infective/inflammatory.

38:34

This is a 60-year-old patient with known,

38:39

uh, multiple myeloma with new complaints

38:42

of fever and abdominal pain and GI bleed.

38:46

Post-contrast CT axial and sagittal reformats

38:51

show diffuse thickening in the rectum and

38:54

sigmoid colon with the comb sign in the adjacent

38:59

mesentery suggestive for active inflammation.

39:02

So the patient was diagnosed with infectious

39:05

colitis and this was the etiology for the.

39:13

Now we're going to move on to some pitfalls of CT.

39:18

And, um, these are factors that will affect our ability

39:22

to visualize and detect, um, active extravasation.

39:27

Firstly, the nature of bleeding — how severe

39:32

it is, is the rate of bleeding

39:36

above that of the threshold for detection?

39:39

Is it intermittent or not?

39:41

If it's intermittent, it's very hard to catch it,

39:44

um, while you are doing the imaging because you

39:46

don't really know when the patient is going to bleed.

39:50

Um, patient factors such as hemodynamic

39:54

status — how is the patient's output?

39:56

Is it, um, adequate to see extravasation or is

39:59

it gonna be quite slow? Patient's body mass index,

40:05

as we all well know, the bigger the patient,

40:08

the poorer the image quality due to the attenuation of photons.

40:13

And this can really limit what we see.

40:17

Pre-existing intestinal contents.

40:20

So hyperdense foods can definitely obscure

40:24

intraluminal contrast extravasation, and this is why

40:28

you do not give positive oral contrast.

40:33

Other factors include dilution of

40:36

contrast in fluid-filled bowel loops.

40:40

So this is kind of like a catch-22 because you need to

40:44

distend, especially in the setting of CT enterography,

40:48

because you want to give, um, adequate amount of neutral

40:52

oral contrast to, um, distend the small bowel loops.

40:56

But at the same time, because you have, um, large

40:59

volume of fluid already in the bowel, it could really

41:03

dilute the, um, extravasated intraluminal contrast.

41:09

Um, inadequate bowel distention with poor

41:12

visualization of tumors or inflammatory lesions.

41:16

I'm sure many of you have tried reading a CT

41:19

enterography for IBD that was not well distended.

41:25

It's very, very difficult, um, to make interpretations,

41:29

um, because of the lack of distention, and, um,

41:34

which goes hand in hand with the second point.

41:36

Um, mucosal enhancement of collapsed

41:38

bowel may simulate extravasated contrast.

41:43

And lastly, hyperdense material like sutures

41:47

and metallic clips or positive oral contrast

41:50

can really, um, impair, um, our detection

41:55

for intraluminal extravasation of contrast.

42:02

Here is a 30-year-old with, um, GI bleeding.

42:07

There's previous resection due to vasculitis.

42:10

So on the post-contrast axial CT, we've

42:15

given positive oral contrast, which is bad,

42:19

bad, bad, and there's also suture material.

42:23

So both of these really obscure the extravasation of

42:27

intravenous contrast. On conventional angiography,

42:33

um, extravasation was seen in keeping with active bleed.

42:39

This was also confirmed on nuclear medicine study.

42:45

This is a 71-year-old patient with a hematocrit drop.

42:50

Post-contrast.

42:51

Axial CT demonstrates a possible

42:53

gastric mass with a hyperdensity

42:58

hyperdense focus adjacent to it.

43:01

So these, these areas may represent

43:04

active arterial bleed, but unfortunately

43:09

positive oral contrast was administered.

43:13

Therefore, the hyperdense foci could not be

43:17

definitively diagnosed as an active bleed.

43:20

Um, here we can see the white arrow.

43:23

There is a contrast-fluid level, so this may

43:26

either be due to extravasated IV contrast

43:29

or simply trapped positive oral contrast.

43:37

This is a 71-year-old patient with GI

43:39

bleed, previous bowel surgery in the jejunum.

43:44

So CT angiography was negative for active bleed.

43:50

Firstly, there's a lack of bowel distension, and that

43:53

could potentially obscure IV contrast extravasation.

43:57

And, um, we have some hyperdense sutures as well.

44:03

Active bleed was seen in the right upper quadrant

44:07

on the nuclear medicine examination, and this was

44:11

also confirmed on, um, conventional angiography.

44:15

And the active bleed is likely adjacent to where the

44:19

suture material was, which we can see on the CT.

44:23

And on the CT,

44:24

the suture material most likely obscured the bleed,

44:28

and, um, therefore we were unable to really detect it.

44:32

So those are the pitfalls we have to keep in mind

44:35

every time we interpret one of these studies.

44:37

Studies.

44:37

Are there any factors, um, either patient or technique,

44:41

that's going to limit our, um, detection for GI bleed?

44:48

So I'm gonna move on to nuclear medicine.

44:52

So nuclear medicine is actually one of the earliest

44:55

reported methods to detect GI bleed.

44:59

It was actually first described in 1977,

45:03

which is, um, way before any of us were born.

45:06

And, um, it is the most

45:08

sensitive, non-invasive technique.

45:10

Just a reminder, it can detect rates

45:13

as slow as 0.1 milliliters per minute.

45:18

So traditionally these were performed with technetium-

45:21

99m sulfur colloid, but this was replaced by tagged red

45:26

blood cells due to, um, limitations from overlying liver

45:31

and spleen uptake when the sulfur colloid was used.

45:36

Um, like CT, the patient has to be

45:39

actively bleeding at the time of scan.

45:42

The advantage is that it is highly sensitive.

45:45

If you've got any patients that have very slow or

45:47

intermittent bleed, this will be the modality to go to.

45:52

One of the biggest disadvantages for

45:55

this is actually localization issues.

45:57

So you see an area of radio-

45:59

tracer uptake, like where is it?

46:01

Is it small bowel, large bowel?

46:03

I mean, you can really only say upper

46:05

quadrant, lower quadrant, left or right.

46:08

But, um, I, I found that the localization

46:12

of bleed can be improved with the use of SPECT.

46:18

Here is a 67-year-old patient with gastrointestinal

46:22

bleed while on anticoagulation therapy.

46:26

Um, planar images of a tagged, um, red blood cell

46:29

scan demonstrate accumulation of tracer in the

46:35

cecum, which is consistent with cecal hemorrhage.

46:39

Um, the CT angiogram and conventional

46:41

angiogram were performed at an outside

46:43

institution and they were negative.

46:46

Um, I don't have those images.

46:48

Um, and this case really illustrates the superior

46:53

sensitivity of nuclear medicine study for slow GI bleed.

47:00

This is a 50-year-old patient

47:03

with gastrointestinal bleeding. Contrast-

47:06

enhanced, um, CT angiogram demonstrates...

47:10

PET, PET — positive oral contrast.

47:13

This was from a prior CT, so this is not really

47:16

their fault, um, which obscures the active

47:19

bleed that we actually see on nuclear medicine study

47:22

and also on conventional, um, angiography.

47:29

Conventional angiography.

47:31

I won't be talking much about this in depth as

47:34

this is not a non-invasive imaging technique.

47:38

Um, it does require a faster

47:41

bleeding rate to be detected.

47:43

It has to be greater than one milliliter per minute.

47:47

Um, however, it does have the advantage of providing

47:50

therapeutic intervention at the time of the examination.

47:57

So, in conclusion, CT angiography is a good first

48:01

line modality for the detection of GI bleed.

48:05

There are limitations to all modalities,

48:08

including nuclear medicine, CT

48:10

angiography, and conventional angiography.

48:15

Contrast extravasation indicating active bleed can occur

48:19

in either or both arterial and venous phases.

48:25

It's important to identify pitfalls when interpreting a

48:29

negative CT angiogram, and intermittent bleeding can be

48:34

common and there are a myriad of causes that we should

48:38

try and look for when we're reviewing a CT for GI bleed.

48:45

Thank you very much.

48:49

Perfect.

48:49

Thank you so much for that.

48:50

I do see some questions in the Q and A

48:51

feature if you'd like to open that up.

48:54

Um, yeah, I am trying to, uh.

49:04

It's not letting my cursor go to my other screen.

49:09

Uh, lemme see.

49:12

You can read.

49:13

You want to

49:13

start?

49:14

Oh, you can do that.

49:14

Oh,

49:15

there we go.

49:15

That will, um, does that work?

49:19

Let me have a look at the Q and A. So, um, maybe I'll

49:24

start from the earliest one, which was from 10:39.

49:27

AM. Um, the question is, many patients take calcium

49:33

supplements. How to differentiate these with GI bleed.

49:37

So I think for, um...

49:39

This particular question, the calcium

49:42

supplements will be hyperdense, correct.

49:45

And you should be able to see them

49:46

on your non-contrast study first.

49:49

And again, if they're there and you do have active,

49:53

um, bleed at that location, it's going to be obscured.

49:56

And that will be a, um, a limitation to your study.

50:01

And, um, I will report it as such.

50:05

And, um, the second question is, how often is nuclear

50:11

medicine study more diagnostic than CT in your center?

50:16

So for us, um, CT...

50:19

Sorry.

50:20

Um, there was another question there.

50:22

So, if CT for us is always a

50:24

workhorse, that's where it goes first.

50:26

And if we don't see anything and they still have

50:28

clinical concerns, then, um, nuclear medicine

50:32

is the secondary study. And oftentimes, actually,

50:36

many times you'll see an area of active extra-

50:41

uh, active bleed that you didn't see on CT.

50:44

So I have found nuclear medicine to be, um,

50:47

very, very useful in these negative CT studies.

50:52

Okay, so the next question that I have here.

50:58

As a negative oral contrast, what you use specifically,

51:02

what's your opinion about, um, 1.5-liter washer with

51:07

0.5 liters of mannitol, and what is their preferred

51:11

time delay which oral contrast is given?

51:16

So, um, this is a really good question.

51:19

We, we use Volumen because we already have,

51:23

um, Volumen on site, um, because we use

51:28

them for the, for the, um, IBD studies.

51:34

And for us, the instruction for Volumen is we want

51:39

the patient to take, um, 450 cc in 20 minutes.

51:47

And then 40 minutes prior, they need to

51:51

drink another 450 cc in 20 minutes, and then

51:56

20 minutes prior, another 450 cc bottle.

52:01

And then on the table, right before they're scanned,

52:05

the patient should drink 220 to 250 cc of water.

52:11

Um, that's just our protocol.

52:14

Um, we don't tend to... I mean, the water

52:17

and mannitol I have seen being used.

52:19

We just don't use it at our institution.

52:24

Okay.

52:24

I'm gonna answer the next question.

52:27

In case a potential pitfall's presented in the patient,

52:32

how should we report the CT angiography scan?

52:35

Should our report specifically contain any

52:38

particular disclaimer lines or any specific

52:41

statement to avoid medico-legal hassles as well

52:45

as to offer a valid explanation to the patient?

52:49

I definitely do that, and I think that's

52:51

why it's so important no matter what you do.

52:54

Um...

52:56

Including, um, GI bleed, you should al—

53:00

always know what are your limitations.

53:03

And I always put it in my report.

53:06

Say for example, um, there is suboptimal distension

53:10

and/or there's positive oral contrast, which

53:13

limits the, um, interpretation of this study.

53:17

And the one other important thing to keep in mind is,

53:20

just because we don't see active bleed, it doesn't mean

53:23

that it's not there because it probably hasn't reached

53:26

the threshold for the bleeding rate to be detected.

53:30

Um, okay, so the next— oh, also, it's also important

53:35

to put the, like, the potential pitfalls because if

53:38

we don't just see it on CT, you are kind of nudging

53:41

the clinician to move on to nuclear medicine study.

53:47

Okay.

53:47

The next question is, in your experience,

53:50

what has been the commonest etiology you have

53:53

found with bleeding from pancreatic pseudo—

53:59

Uh, commonest etiology found?

54:02

I'm not entirely... uh, from pancreatic pseudos...

54:07

I'm not entirely sure what the question means.

54:13

Um, I've actually not seen many

54:16

bleeding from pancreatic pseudos.

54:19

I think the most common etiology I have

54:22

seen—so the majority of these, um, CT

54:25

angios are negative for active bleed.

54:28

So it could either be chronic or, um, slow

54:31

bleed below the threshold for detection.

54:34

It's actually incidental colon cancers

54:37

that I have seen quite a few of.

54:39

And so that's really important, and

54:41

that's when the radiologist can really,

54:43

really change the direction of management.

54:48

Okay, so next question.

54:51

Radial bleeding needed to be detected.

54:54

So if I come back to my— so you want

54:58

to know, I'm gonna take the question

55:00

as you want to know what the rates are.

55:04

So, um, for nuclear medicine scan, it's

55:07

greater than 0.1 to 0.2 milliliters per minute.

55:13

For CT, it's greater than 0.35 milliliters per minute.

55:19

And for conventional, it has to be

55:22

greater than one milliliter per minute.

55:28

Okay, so that's that question.

55:31

The role of SPECT and CT.

55:33

So like I said before, the biggest problem with

55:36

nuclear medicine study is the localization.

55:40

And SPECT is wonderful and, um, for me,

55:44

I feel like it really does change a lot.

55:47

So if you don't know where it is, SPECT it, um, that's

55:54

the bottom line.

55:55

Okay.

55:56

In postoperative leak, we should

55:58

not also give oral contrast.

56:01

Um, you mean they want to look for

56:04

bleed as well as a postoperative leak?

56:06

Um, in those cases, you kind of need to have

56:09

a discussion with the clinician and say, well,

56:12

which do you think is the most likely scenario?

56:15

So in postoperative leak, you have to

56:18

give oral contrast, um, because you

56:21

wanna see where it's leaking from.

56:22

That will be the definitive, um, thing to do.

56:25

And it also helps them localize

56:27

where the leak is coming from.

56:29

Um, for if they want to know if there's GI

56:32

bleed, do not give positive oral contrast.

56:37

Okay.

56:38

Uh, the next question is when to do CT

56:40

angiogram and when to do enterography.

56:44

I think, um, the most important thing is

56:47

where does a clinician think the problem is?

56:51

So if they think really it's a small bowel issue,

56:54

I would go for a CT enterography triple phase.

56:58

Okay.

57:00

In cases, if active GI bleed is greater than one

57:05

cc per minute, and patient, he...

57:12

do.

57:13

Recommend CT angiography or laparotomy.

57:18

Okay, so you are saying that,

57:20

um, they're bleeding quite fast.

57:24

Well, uh, greater than... So if the patient is

57:28

hemodynamically stable, well, um, really you should

57:33

do a CT an—um, angiogram because the angiogram

57:37

really show, like we said, have shown that, um,

57:40

non-invasive imaging when performed before any

57:43

sort of, um, intervention can be—can have higher,

57:48

um, yield in terms of, um, patient outcomes.

57:52

Laparotomy is really reserved for patients who, um,

57:57

you think there's going to be a high risk of exsanguination.

58:02

The next one.

58:03

Oh, thank you, Dr. Gomez, for your kind comment.

58:08

Um, next question is.

58:12

In some patients there is no frank GI

58:15

bleed, but only drop in hematocrit.

58:18

Do you recommend doing GI bleeding study in

58:20

such patients and do we need to detect or

58:23

occult blood to make sure it is GI bleeding?

58:26

Um, so yes and no.

58:31

Sometimes a, um, huge... sorry.

58:35

I'm gonna, uh, as such, do we need to detect

58:38

the occult blood. In my institution, basically,

58:44

anyone who has a drop in hematocrit, um,

58:47

they get a CT angiogram and that's what they

58:50

do. I think to, um, do a fecal occult blood

58:55

may not be feasible in acute cases.

59:01

Okay, next question.

59:02

Do we re—really need positive

59:04

oral contrast in any CT abdomen?

59:08

Thank you for the wonderful lecture.

59:10

Thank you so much for your, um, lovely comment.

59:13

So this is very contentious and you'll find

59:17

people sway differently about how attached

59:21

they're to or not to positive oral contrast.

59:25

We do not give positive oral contrast in the

59:27

ER setting because we know they're trying

59:30

to, um, diagnose a patient and manage them

59:34

as fast as possible.

59:38

But every other study, if the patient

59:42

is able to tolerate positive oral

59:43

contrast, we still give it to them.

59:45

In our institution, and this is completely

59:48

variable depending on the institution you talk to.

59:53

Okay, next one is radiation exposure in CT angiogram

59:59

versus CT bleed scintigraphy plus or minus SPECT CT.

60:09

I'm gonna be honest, I am not entirely sure

60:12

what the radiation exposure is for the radio.

60:16

Um, for the nuclear medicine studies plus SPECT, I

60:19

suspect it would be much less than a CT angiography.

60:23

The reason being that the CT angiography is three-phase.

60:28

So you basically have three studies from the, um,

60:32

the diaphragm down to the, um, pubic symphysis.

60:37

And because a lot of our patients are slightly on

60:41

the larger side, then you really need to amp up,

60:44

um, your photons, which increases in radiation.

60:49

So I can't give you a definitive answer because

60:51

I'm, I cannot tell you the exact figures of

60:54

radiation exposure, but that is what I surmise.

60:59

Last question.

61:00

Uh, next question.

61:01

Sorry, though.

61:04

1001 01:01:04,485 --> 01:01:07,125 Appropriateness criteria clearly indicates,

61:07

endoscopy and colonoscopy as first line.

61:10

Clinical services always insist on CT angiography.

61:15

How do you deal with this in your institution?

61:18

So this is really a conversation that,

61:21

needs to be had with the clinicians.

61:24

I find that, um, first of all, they may not know that,

61:28

we have these appropriateness guidelines and, um.

61:34

It's good to have this, firstly, have,

61:35

a conversation, see what they think.

61:38

Um, endoscopy, the prep is much less.

61:41

So I find that our clinicians don't have, um,

61:44

much of an issue trying to do endoscopy, but,

61:47

colonoscopy, like I said, and in the document as well.

61:51

If the patient cannot do appropriate,

61:54

preparation, then it's gonna be super difficult.

61:57

Like when the co, um, colonoscopy goes in,

61:59

all they're gonna see is fecal material,

62:01

and it's gonna obscure everything.

62:04

And in those cases, I think CT angiogram is,

62:07

um, comparative and it's a very, it's a good,

62:10

first line, um, which is what also the, um,

62:13

appropriateness guidelines, um, talks about.

62:18

Next one.

62:19

Can you please repeat what the,

62:20

contraindications for CT angiography?

62:25

So, the biggest contraindication for any,

62:28

CT with intravenous contrast is really, um.

62:34

Anaphylaxis. Anaphylaxis, you would,

62:38

never give intravenous contrast.

62:40

Um, even you would not give them pre, um,

62:43

premedication either, because that doesn't really help.

62:46

Um, some of the other contraindications,

62:50

include like poor renal function, but that's usually,

62:54

a discussion you can have with the clinician and,

62:56

um, see how clinically relevant or, um, needed this,

63:02

CT is and usually a nephrologist gets involved.

63:07

Okay, next question.

63:10

In those cases where you find angiodysplasia,

63:13

do you always have to look for another,

63:15

cause of bleeding in your practice?

63:17

What's the most commonest cause of,

63:18

bleeding on imaging that you have found?

63:21

So, yes.

63:22

Um, the reason why I showed that particular case,

63:25

where there was bleeding from different segments,

63:27

of the small bowel is the satisfaction of search.

63:31

Even if you found one area of bleed.

63:35

It doesn't mean that they cannot,

63:36

they're not others, right?

63:38

So it's always important, and as tedious as it's,

63:42

to look through the entire, um, large and small,

63:46

bowel to see if you can find any other cause of,

63:49

bleeding because you don't really want to miss it.

63:52

Right.

63:52

And, um, common cause of bleeding or imaging.

63:57

I think with the aging population, um, colon cancer,

64:01

it's very high on the list as the cause of bleeding.

64:05

And like I said before, it really completely,

64:08

changes, um, the management course of that patient.

64:12

And that's, and it's solely based on,

64:15

you being able to detect that on CT.

64:19

Okay.

64:19

Um, next question.

64:21

Amazing lecture.

64:22

Thank you.

64:23

Thank you for the kind comment.

64:24

Um, in cases of GI bleeding, we do CT,

64:27

angiogram and CT enterography in some cases.

64:31

So when should we start with CT enterography?

64:34

So the, that had this discussion with one of,

64:36

our gastroenterologists and, and CT enterography,

64:40

should be first line if you, if the clinician,

64:43

thinks that it's small bowel etiology.

64:46

So if they say, I think it's small bowel,

64:49

um, upper lower scopes are completely,

64:52

clean, and that CT enterography triple-phase,

64:56

will be the next, um, next place to go.

65:00

Okay.

65:01

Last question.

65:02

For CT angiography for GI bleed, do you,

65:06

give negative oral contrast such as mannitol?

65:10

So we had this discussion, um, previously in one,

65:13

of the earlier, earliest earlier questions.

65:16

So in my particular institution we use, um, the lumen,

65:20

but I have seen places use, um, water and mannitol.

65:24

It's really an institution-based thing,

65:28

so everyone's gonna be slightly different.

65:34

Okay.

65:34

And then how to differentiate bleeding of arterial.

65:39

So arterial origin is going to be, if you see, if,

65:43

you see something extravasate on the arterial phase,

65:46

and it changes configuration on the venous phase,

65:49

you know, that's definitely arterial bleed, right?

65:51

Because the extravasation starts in the arterial phase.

65:56

The trouble is the, um.

66:02

When you see it on venous phase, it doesn't,

66:04

necessarily mean that it's not arterial.

66:07

It may be very slow or delayed, or venous in origin.

66:13

So I think when it bleeds, when it extravasates on,

66:17

the arterial phase, you can be much more definitive.

66:20

But when it bleeds or you can see the bleeding on the

66:23

venous phase, it's kind of, you can't really tell.

66:29

Okay.

66:29

And then one more question.

66:31

Um, what is pseudo vein appearance?

66:37

I'm not sure what that question is, as in, um,

66:43

it looks like it's a vein and it really isn't.

66:47

I, I'm gonna take that question as that.

66:49

So like, um, all linear structures,

66:51

they could possibly be, um.

66:55

Vessels rather than true extravasation.

66:58

But remember when you look at, for,

67:01

extravasation, it should be intraluminal,

67:04

so it should be bleeding into the lumen.

67:07

So, um, if it's outside of the lumen, as in the linear,

67:12

things are outside of lumen, it's probably, it's, it's,

67:15

not, um, act, it's not going to be for the, it's gonna,

67:21

be more likely a vessel than, um, active GI bleed.

67:28

And I think that's our last question.

67:30

I think it is too.

67:31

So as it brings us to a close, I'd like to,

67:32

thank you Dr. Wang for your time today.

67:33

We really appreciate it.

67:34

And thanks all you participating,

67:36

in this noon conference.

67:37

A reminder that it will be made available,

67:38

on demand complimentary @mrionline.com in,

67:41

addition to all previous noon conferences.

67:43

And tomorrow, please join us for our,

67:44

conference with Dr. Saka Sheikh, um, on,

67:47

PET/CT of Infection and Inflammation.

67:50

Thank you and have a wonderful day.

67:53

Thank you.