0:00

We've been talking about ischemia to

0:02

the gut for many, many weeks

0:04

now. We've talked about celiac arteries,

0:06

superior mesenteric arteries. We've talked about

0:09

blood clots going to the abdomen

0:11

causing infarctions, even chronic mesenteric

0:13

ischemia which causes forms of angina that

0:15

normally people feel in their chest, but

0:18

with patients who have chronic mesenteric ischemia,

0:20

it's in the abdomen. Now

0:22

this week, we're going to round

0:24

out our topic of ischemia, which

0:26

is basically that reduction of blood

0:28

flow that's insufficient for the delivery

0:31

of oxygen, talking about colonic ischemia.

0:33

Now, believe it or not, colonic

0:35

ischemia is the most frequent form

0:37

of intestinal ischemia and it affects

0:39

mostly older patients. You're going to see this

0:41

a great deal. And for most of you,

0:43

you've probably run across this in your inpatient

0:45

rotations, but approximately 15% of

0:48

patients with colonic ischemia actually

0:50

develop necrotic bowel. So

0:52

it's important for us to understand how

0:55

to make the diagnosis and who needs

0:57

what kind of treatment. I'm Dr. Niket

0:59

Sanpal, your friendly neighborhood internist and gastroenterologist

1:01

and podcast host. Let's jump into the

1:03

topic. Now

1:16

we know that the colon itself is

1:18

very, very vulnerable to hyperperfusion. And when

1:21

we talk about the colon, which part

1:23

of it is most susceptible to ischemia,

1:25

it's the mucosa and the reason why

1:27

it's furthest from blood supply. Now

1:30

the blood supply of the colon and the

1:32

rectum is primarily from the SMA, the IMA,

1:34

and the internal iliac arteries. And

1:37

for the purposes of discussion, there are

1:39

two types of ischemic colitis. There's the

1:41

embolic and thrombotic arterial occlusion type, which

1:44

is very, very rare, less than 5%.

1:46

And the type that you're most

1:48

familiar with, the non-occlusive type, or the one that

1:50

we call the low blood flow type. This

1:52

has brought 95% of the cases that you've seen in the hospital.

1:56

And during rounds and during your preclinical

1:58

and even rotation days, Because you remember the

2:01

term watershedty areas, and these are the

2:03

parts of the colon that have limited

2:05

collateralization. Which ones are these?

2:07

Well, it's the splemic flexure and the

2:09

rectosigmoid junction. In large studies

2:12

looking at thousands of patients, the left colon

2:14

was involved 75% of the time in

2:17

ischemic colitis. So when your patients come

2:19

in, they're going to have that left lower quadrant

2:21

pain. So let's go ahead and talk

2:23

about some risk factors and how they're going to present. Now

2:26

the risk factors for it are actually kind

2:28

of vast. You see patients who are predisposed

2:31

to colonic ischemia could pretty much have no

2:33

identifiable risk factors or have a lot. Hemodialysis

2:35

patients are really susceptible to it

2:38

because they have massive shifts in

2:40

volume states between intravascular and extravascular

2:42

places. And so therefore they're

2:44

very, very susceptible to hypotension. In

2:47

addition, anything that's going to mess with

2:49

cardiac output, CHF, myocardial infarctions is also

2:51

going to play a role. Changes

2:53

in medications, for example, hypertension medications

2:55

can sometimes drop the pressures too

2:57

much. Any kind of major

2:59

surgeries can do this. And even extreme exercise.

3:02

Isn't that something? That's right. Marathon runners,

3:04

triathlon patients, they come in all the

3:07

time with severe abdominal pain and it

3:09

turns out it's intestinal ischemia. Now that's

3:11

not me saying don't go out on

3:14

exercise. Exercise is great for

3:16

you, but a pizza never gave you ischemic

3:18

colitis. Just saying. And

3:20

then there are numerous other risk

3:22

factors like for example, certain types

3:24

of viral infections, ischemic changes related

3:26

to sepsis and even colonoscopies have

3:28

sometimes been related to what we

3:31

call barotrauma. And that barotrauma can

3:33

sometimes happen from the air that we put into

3:35

the colon and can actually cause damage to the

3:37

lining of the colon due to blood flow changes.

3:40

But essentially your take home lesson is

3:42

anything that's going to drop the flow

3:44

of blood to the gut leading to

3:46

hypotension, leading to low flow states in

3:48

which the mucosal layer gets less blood

3:50

than the rest. And like

3:52

the Nicolas Cage movie Gone in 60 Seconds, without

3:55

oxygen you lose that ability to have ATP, they

3:57

become ischemic, they die, you get pain, you get

3:59

pain. bleeding, but it's much more than that. So

4:01

let's talk about how the patients are going to

4:03

present. Your patient's presentation is going to

4:05

be very, very classical. The first thing that's going

4:07

to happen is there'll be an antecedent history of

4:09

some reason for them to have dropped their blood

4:12

pressure or dropped blood flow to the gut. Let's

4:14

say a really bad gastroenteritis. Maybe they ran a

4:16

marathon. Maybe they just started recovering from

4:18

a bad flu. The point is

4:20

they're going to start to have that low

4:23

flow state. The lining of the gut gets

4:25

ischemic and that ischemic pain occurs.

4:27

And then there's this mild

4:29

cramping abdominal pain and tenderness

4:31

over the affected part that became

4:34

ischemic. Most commonly, the lower left

4:36

quadrant. That is then going to cause them

4:38

to feel like they have to go to the bathroom.

4:40

Some patients have even told me that cramping

4:42

feels like the quote unquote pressure you get

4:44

after having a cup of coffee in the

4:46

morning, but it's more painful. And so they

4:49

run to the bathroom and sometimes that need

4:51

to defecate and that cramping can then

4:53

be followed by a bowel movement,

4:55

but it's actually hematochesia. Most

4:57

patients will actually have about mild to

5:00

moderate amounts rectal bleeding. And remember,

5:02

when there's more ischemia on the left, you're obviously

5:04

going to have more bleeding. Right colonic

5:06

ischemia, which is rarer, has less bleeding,

5:08

which just simply makes sense based on the

5:10

presentation. And of course, the side of the

5:12

colon we're talking about. Now, the most common

5:15

question I get asked on rounds is, is

5:17

the blood loss severe? It usually tends to

5:19

be mild and doesn't necessarily require blood transfusions

5:21

unless this is an acute on chronic anemia

5:24

that's being exacerbated. Once this

5:26

phase passes, most patients, if they have some

5:28

reason to get their blood pressures back up

5:30

on their own, they'll do okay. But if

5:32

the ischemia continues, then the bowels

5:34

basically become iliotic. In other words, they get

5:37

a paralytic state, the patient becomes distended, they

5:39

may even become nauseated. And if

5:41

it still continues, and let's say their blood pressures

5:43

are still not recovering. Now the

5:45

ischemia becomes that 10 to 20% of

5:47

patients I mentioned earlier, in which they

5:50

go into shock, and the bowel actually

5:52

dies completely. And they present with metabolic

5:54

acidosis and usually need surgery. But

5:56

for the vast majority of the patients, it's

5:59

usually just cramping and lower GI bleeding.

6:01

And so when you see these patients,

6:03

you're gonna do anything you normally would

6:06

do for a patient who comes with

6:08

a lower GI bleed. You're gonna resuscitate

6:10

the patient, you're gonna check blood counts,

6:12

coagulation profiles, metabolic profiles. There's no specific

6:14

lab to check, but if you're suspecting

6:16

ischemia based on the cramping followed by

6:18

bloody diarrhea state, you can check a

6:21

LDH and it could be mildly elevated,

6:23

but it's gonna be nowhere near as

6:25

high as somebody comes in with mesenteric

6:27

ischemia. They're having gut death. In patients

6:29

with ischemia colitis, it might be mildly

6:32

elevated from that temporary period of anaerobic

6:34

respiration. The other thing you

6:36

wanna make sure these patients are ruled out

6:38

for is gonna be clostridioides difficile. Remember, a

6:41

lot of times, bloody diarrhea can be common

6:43

with ischemia colitis or lower GI bleeds, but

6:45

some patients can sometimes present with C.

6:47

diff with bloody diarrhea, not commonly,

6:50

but it does need to be ruled out. The next

6:52

step in management after this is gonna be the

6:54

workup. You're gonna get an X-ray, and

6:56

this is primarily to make sure that you're not

6:58

dealing with a distended abdomen and obstruction, and more

7:01

importantly, you wanna rule out free air so you

7:03

haven't missed a perforation. Once all

7:05

your labs come back and that X-ray shows nothing in

7:07

the C. diff testing, which is probably cooking is going

7:09

on, your next step in management is to get

7:11

the most accurate test, which is gonna be a

7:13

CT scan of the abdomen with oral contrast and

7:16

IV contrast if the patient's crayon and can tolerate,

7:18

and oral contrast primarily is important because you wanna

7:20

be able to see the edema on the walls,

7:22

but that's also if they're not having nausea and

7:25

vomiting. Most of them do not, but it's important.

7:27

And what are some of the terminologies your patients are gonna

7:29

have when they get back for their reports from

7:31

the radiologist? Well, they're gonna tell you that

7:34

the bowel wall is edematous and thickened, which

7:36

we expect in colitis. There may

7:38

be something called a target or double halo sign.

7:40

What this is is basically hyperdensity from the

7:42

mucosa and muscularis. It can also find thumb

7:45

printing, and most importantly, it'll also look for

7:47

things like pneumatosis coli. This is gonna be

7:49

gas in the mesenteric or portal veins and

7:51

in the wall of the gut. The reason

7:54

why we wanna make sure the patient doesn't

7:56

have those is that's basically a sign of

7:58

colonic necrosis. Now the CT scan

8:01

is the most accurate test and the

8:03

most commonly employed before we begin treating

8:05

the patient. But there actually is the

8:07

gold standard test, which is a colonoscopy.

8:09

And you wanna offer it to patients

8:11

in all cases with colonic ischemia if

8:13

they're stable, or at least it should

8:16

be done somewhat afterwards. The reason why

8:18

is because the gold standard of diagnosis,

8:20

because it's a mucosal disease, is mucosal

8:22

biopsies, which you get through colonoscopy. Now

8:24

the decision to actually do the colonoscopy

8:26

in the setting of ischemic colitis is

8:29

patient by patient. It should be offered

8:31

if the patient's stable and should be done

8:33

with minimal air and suflation, so we don't

8:35

overly distend the colon and cause a perforation.

8:38

Now, if the patient is risk stratified to basically having

8:40

mild colonic ischemia, the CT scan may be enough.

8:42

But if it's moderate to severe, we may need

8:45

to go in and kind of get a sense

8:47

of where it is. And that's where the colonoscopy

8:49

really plays a role before we start treatment. But

8:52

regardless of the way that you get

8:54

your actual diagnosis, most commonly gonna be

8:56

through CT scan, your next step in

8:59

management, believe it or not, is supportive

9:01

care. That's right, most of these patients

9:03

will have either mild or moderate symptoms.

9:05

And the treatment for this is gonna

9:07

be primarily bowel rest, observation, making sure

9:09

the person doesn't progress to perforation and

9:12

necrosis. And of course, crystalloid or colloid

9:14

resuscitation. Crystalloids is usually preferred with IV

9:16

fluids to ensure adequate colonic perfusion and

9:18

oxygen delivery. Some patients like to drop

9:20

an NG tube. We tend to usually do

9:22

it only if the person has an ilius and it's

9:24

more severe. In addition to that, we usually try to

9:27

keep the patient NPO, as I said, with bowel rest,

9:29

and then we monitor their labs. Now

9:31

in that discussion of supportive care, I never

9:33

said the word ciproflageal or ceftriaxone and flageal,

9:35

now did I? Ciproflageal is such a knee-jerk

9:37

reaction for all of us. But antibiotics

9:40

do play a role. The thing

9:42

is, is that there's no real strong

9:44

evidence for it. However, multiple society guidelines

9:46

say that empiric broad-spectrum antibiotics should be

9:49

given to patients with colonic ischemia. And

9:51

with those management steps, the patients tend to get better.

9:53

They'll start tolerating diet and we'll be able to go

9:55

home. The next thing you have to do is find

9:57

out why they became ischemic and counsel the patients not.

10:00

to do those things. Like for example, if

10:02

it was a marathon, it might be better

10:04

just to get some pizza. Now, for the

10:06

patients who don't get better, you want to

10:08

get your surgical colleagues on board because surgery

10:10

is required in up to 20% of these

10:12

patients. Bowel necrosis and infarctions can occur and

10:14

without surgery, it can be lethal. And

10:17

with that, folks, brings us to the end of

10:19

this series on all things abdomen and ischemia. I'm

10:22

Dr. Niket Sonpaul, your friendly-neighbor internist and gastroenterologist.

10:24

I hope you've enjoyed this series. Join me

10:26

next week where we kick off the Medgeeks

10:28

podcast with a brand new series on a

10:30

whole bunch of new topics. See you then.