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Flashcards in Ischemic Bowel Disease Deck (52)
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1

Ischemic Bowel Disease
1. Changes how with age?
2. Mortality?
3. Patterns? 4

1. Increases with age

2. High mortality, 50~90%

3. Patterns:
-small and/or large bowel
-diffuse or localized
-segmental or focal
-superficial or transmural

2

4 Major causes of Acute Mesenteric Ischemia

1. SMA embolism—50%
2. SMA thrombosis—15-25%
3. Nonocclusive ischemia—20-30%
4. Mesenteric venous thrombosis—5%

3

1. SMA thrombosis is often imposed on what?
2. Also occurs with what? 2

1. Often superimposed on patients w/ progressive atherosclerotic disease

2. Also occurs w/ trauma or infection

4

Acute mesenteric ischemia
1. Occlusive causes? 3
2. Non-occlusive causes? 1

1. Occlusive
-Mesenteric arterial embolism
-Mesenteric arterial thrombosis
-Mesenteric venous thrombosis

2. Non-Occlusive
-Hypoperfusion

5

Circulation to the intestines
1. Primarly through what? 2

2. Requires how much of our cardiac output?

1. Primarily SMA and IMA
-Lots of collateral circulation

2. Requires 10-35% of the cardiac output

6

Regulation of intestinal circulation: In what ways?
5

1. Perfusion pressure
2. Neural and hormonal mechanisms
3. Sympathetic nervous system,
4. Renin angiotensin system,
5. vasopressin from the pituitary

7

What does vasopression do for the intestinal vasculature?
2

Vasopressin
1. Causes mesenteric (arterial) vasoconstriction and venous dilation
2. Reduces portal venous pressure in patients bleeding from portal hypertension

8

Acute mesenteric ischemia: Hallmarks of clinical presentation
3

1. Severe cramping abdominal pain,
2. out of proportion of physical findings,
3. poorly localized

9

Acute mesenteric ischemia: Clincial presentation
1. Abdominal exam?
2. Occult blood sample?
3. As bowel ischemia worsens what will happen? 4

1. Abdominal exam may be normal initially
2. Occult blood in stool

3. As bowel ischemia worsens
-Abdominal distention
-Absent bowel sounds
-Peritoneal signs
-+/- feculant odor to the breath

10

Risk factors associated with acute mesenteric arterial embolism
11

1. Advanced age
2. Coronary artery disease
3. Cardiac valvular disease
4. History of dysrhythmias
**Atrial fibrillation
5. Post-myocardial infarction mural thrombi
6. History of thromboembolic disease
7. Aortic surgery
8. Aortography
9. Coronary angiography
10. Aortic dissection
11. CHF

11

Mesenteric arterial embolism
1. What demographic affected mostly?

2. What artery does it involve and affects what structure?

3. Where?

1. Median age: 70, 2/3 are woman

2. Superior Mesenteric Artery often involved and affects the jejunum

3. 6-8 cm beyond the arterial origin, near middle colic artery

12

Mesenteric arterial embolism
1. Comes from where?
2. What also occurs to promote the embolism?
3. Clinical presentation? 4

4. Prognosis compared to SMA thrombosis?

1. Thrombus from L atrium, L ventricle or cardiac valves:
--Over 20% of cases have emboli multiple

2. Arteriolar vasoconstriction also occurs

3.
-Sudden onset of severe pain, that is out of proportion to the physical findings 75%
-Nausea, vomiting,
-frequent bowel movement
-Occult blood in stool 25%

4. More favorable prognosis than SMA thrombosis

13

Mesenteric arterial thrombosis usual suspects
4

1. Atherosclerotic disease
2. Trauma
3. Infection
4. Does not appear to be associated with a coagulopathy

14

Mesenteric arterial thrombosis
1. Hx of?
2. Usual site of blockage is what? 2
3. Prognosis?
4. When do symptoms develop?

1. Usually can elicit a history of chronic mesenteric ischemia

2. Usual site of blockage is the
-origin of the SMA or
-celiac axis

3. Less favorable prognosis

4. Symptoms do not develop until significant blockage (collateral circulation) which can complicate revascularization

15

Mesenteric venous thrombosis
1. In what population of ppl?
2. Onset?
3. Thrombosis of superior mesenteric vein or?

4. 30% of the cases involve thrombosis of what?

1. Younger population 48~60 y/o
Primary 20%
Secondary 80%

2. Onset can be acute or develop over the course of a few weeks

3. Thrombosis of superior mesenteric vein or
- intestinal strangulation from hernia or volvulus

4. thrombosis of the portal vein

16

Mesenteric venous thrombosis:
Longer symptoms presentation
5

Sympotom onset?

1. Pain diffuse and nonspecific initially, but later becomes constant
2. Anorexia 53-54%
3. vomiting 41-77%
4. diarrhea 36%, constipation 13-34%
5. hematemesis 9-42%

More insidious onset of symptoms

17

Mesenteric venous thrombosis
risk factors?
9

1. Hypercoagulable state (up to 75% have a hypercoagulable disorder)
2. Portal hypertension
3. Abdominal infections
4. Blunt abdominal trauma
5. Pancreatitis
6. Splenectomy
7. Malignancy in portal region
8. Personal or family history of DVT or PE
9. Dehydration

18

Intestinal ischemia in mesenteric venous thrombosis pathophysiology

6 steps to the end result?

1. Decreased mesenteric venous blood flow

2. Results in bowel wall edema (tons of this!!! this is how you know its venous and not arterial)

3. Fluid efflux into the bowel lumen

4. Results in systemic hypotension & an increase in blood viscosity

5. This results in diminished arterial flow

6. Leading to submucosal hemorrhage & bowel infarction

19

1. Nonocclusive mesenteric ischemia is a result of what?
2. Risk factor?
3. Often the pt has what? 2

1. Result of splanchnic hypoperfusion & vasoconstriction
2. Risk factor—atherosclerotic disease
3. Often the patient has a
-life-threatening illness/
-is being treated e.g. CHF, MI, sepsis etc.

20

Nonocclusive mesenteric ischemia: Pathogenesis
1. In general?
2. How does this happen? 2

1. mesenteric vasospasm

2.
-Homeostatic mechanism maintains cardiac and cerebral blood flow
-Vasopressin & angiotensin involved

21

Nonocclusive mesenteric ischemia
1. Mortality?
2. Severity and location of pain may be different than occlusive mesenteric ischemia. Presentation? 4

1. high mortality -up to 70%

2.
-Progressive abdominal pain,
-bloating,
-N/V,
-mental status changes


Up to 25% of patients do not have abdominal pain

22

What if the ischemia is in the colon?
1. 90% of pts are of what age?
2. How do patients appear?
3. Presentation? 4
4. Dx?

1. 90 percent of patients over age 60 years

2.
-Acute precipitating cause is rare
-Patients do not appear severely ill

3.
-Mild abdominal pain,
-tenderness present
-Rectal bleeding,
-bloody diarrhea typical

4. Colonoscopy is procedure of choice

23

Summary of the etiology of acute mesenteric ischemia
1. Aterial emboli? 2
2. Arterial thrombosis? 1
3. Venus thrombosis? 2
4. Nonocclusive mesenteric flow? 1

1. Arterial emboli:
-Atrial fibrillation,
-MI

2. Arterial thrombosis:
-Atherosclerotic disease

3. Venous thrombosis:
-Underlying disorder in coagulation (hypercoagulable),
-neoplasm

4. Nonocculsive mesenteric ischemia:
-Low flow states

24

Acute mesenteric ischemia workup?
2

1. Lab
2. Imaging

25

Which labs for Acute mesenteric ischemia ?
5

1. ↑WBCs with predominance of immature cells
2. ↑HCT (hemoconcentration)
3. ↑Amylase (50%), ↑phosphate (80%)
4. ↑Serum lactate
--77-100% sensitivity/42% specificity
5. Metabolic acidosis

26

Which imaging tests for Acute mesenteric ischemia?
2

1. Plain abdominal x-rays
2. CT scan of the abdomen

27

Any patient with 1._____________ and 2._____________ has intestinal ischemia until proven otherwise

1. abdominal pain
2. metabolic acidosis

28

Imaging – Plain X-rays will show?
6

1. Pneumatosis intestinalis
2. Portal venous gas
3. Thickened bowel wall with thumb-printing
4. Air fluid levels
5. Dilated bowel loops
6. Gasless abdomen

29

In cases of surgically proven acute mesenteric ischemia:
what will you find on the XRAY? 5

1. Air fluid levels 67%,
2. Dilated bowel loops 18%,
3. Gasless abdomen 10%,
4. Pneumatosis 2%,
5. Portal venous gas 2%

30

1. What is Pneumatosis intestinalis?

2. Suggestive of what?

1. Gas cysts in the bowel wall
(It is not gas in the bowel lumen)

2. Suggestive of necrotizing enterocolitis