Ischemic Bowel Disease

Question 1

Ischemic Bowel Disease

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

Answer 1

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

Question 2

4 Major causes of Acute Mesenteric Ischemia

Answer 2

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

Question 3

1. SMA thrombosis is often imposed on what?

2. Also occurs with what? 2

Answer 3

1. Often superimposed on patients w/ progressive atherosclerotic disease
2. Also occurs w/ trauma or infection

Question 4

Acute mesenteric ischemia

1. Occlusive causes? 3
2. Non-occlusive causes? 1

Answer 4

1. Occlusive
   - Mesenteric arterial embolism
   - Mesenteric arterial thrombosis
   - Mesenteric venous thrombosis
2. Non-Occlusive
   - Hypoperfusion

Question 5

Circulation to the intestines
1. Primarly through what? 2

2. Requires how much of our cardiac output?

Answer 5

1. Primarily SMA and IMA
   - Lots of collateral circulation
2. Requires 10-35% of the cardiac output

Question 6

Regulation of intestinal circulation: In what ways?

5

Answer 6

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

Question 7

What does vasopression do for the intestinal vasculature?

2

Answer 7

Vasopressin

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

Question 8

Acute mesenteric ischemia: Hallmarks of clinical presentation
3

Answer 8

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

Question 9

Acute mesenteric ischemia: Clincial presentation

1. Abdominal exam?
2. Occult blood sample?
3. As bowel ischemia worsens what will happen? 4

Answer 9

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

Question 10

Risk factors associated with acute mesenteric arterial embolism
11

Answer 10

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

Question 11

Mesenteric arterial embolism
1. What demographic affected mostly?

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

Answer 11

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

Question 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?

Answer 12

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

Question 13

Mesenteric arterial thrombosis usual suspects

4

Answer 13

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

Question 14

Mesenteric arterial thrombosis

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

Answer 14

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

Question 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?

Answer 15

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

Question 16

Mesenteric venous thrombosis:
Longer symptoms presentation
5

Sympotom onset?

Answer 16

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

Question 17

Mesenteric venous thrombosis
risk factors?
9

Answer 17

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

Question 18

Intestinal ischemia in mesenteric venous thrombosis pathophysiology

6 steps to the end result?

Answer 18

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

Question 19

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

Answer 19

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.

Question 20

Nonocclusive mesenteric ischemia: Pathogenesis

1. In general?
2. How does this happen? 2

Answer 20

1. mesenteric vasospasm
2. • Homeostatic mechanism maintains cardiac and cerebral blood flow
   • Vasopressin & angiotensin involved

Question 21

Nonocclusive mesenteric ischemia

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

Answer 21

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

Question 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?

Answer 22

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

Question 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

Answer 23

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

Question 24

Acute mesenteric ischemia workup?

2

Answer 24

1. Lab

2. Imaging

Question 25

Which labs for Acute mesenteric ischemia ? | 5

Answer 25

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

Question 26

Which imaging tests for Acute mesenteric ischemia? | 2

Answer 26

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

Question 27

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

Answer 27

1. abdominal pain | 2. metabolic acidosis

Question 28

Imaging – Plain X-rays will show? | 6

Answer 28

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

Question 29

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

Answer 29

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

Question 30

1. What is Pneumatosis intestinalis? | 2. Suggestive of what?

Answer 30

1. Gas cysts in the bowel wall (It is not gas in the bowel lumen) 2. Suggestive of necrotizing enterocolitis

Question 31

1. Portal venous gas is what? | 2. A variety of causes such as what? 2

Answer 31

1. Accumulation of gas in the portal vein and it’s branches 2. A variety of causes such as - ischemic bowel, - intra-abdominal sepsis

Question 32

What are the first step in evaluation of the acute abdomen?

Answer 32

Upright and supine plain abdominal x-rays

Question 33

What will you see on xrays that are suggestive of bowel ischemia? 5

Answer 33

1. Free air, 2. obstruction, 3. ileus, 4. intussusception, 5. volvulus Mesenteric ischemia is difficult to diagnose on plain films alone

Question 34

What is the next step if the dx is not made on plain films?

Answer 34

CT

Question 35

CT is the preferred imaging study: appearance will vary based on what? 7

Answer 35

1. Cause 2. Severity 3. Localization 4. Extent and distribution 5. Presence and degree of submucosal or intramural hemorrhage, 6. superimposed bowel wall infection, or 7. bowel wall perforation

Question 36

1. CT with or without contrast? | 2. What about if ordering a CT angiogram?

Answer 36

1. Oral and IV contrast Oral contrast necessary for evaluation of the mucosal thickening of the bowel wall 2. If just ordering a CT angiogram (CTA) may not want to have oral contrast because it can obscure the view of the mesenteric vessels

Question 37

CT findings | 5

Answer 37

1. Bowel wall thickening 2. Bowel dilation (can be assoc. with wall thinning) 3. Fat stranding and ascites 4. Varying degrees of attenuation - High attenuation (white) - Low attenuation (black) 5. Pneumatosis and portomesenteric gas

Question 38

What is the most common finding in ischemic colitis, colonic infarction, and venous occlusion?

Answer 38

Bowel wall thickening

Question 39

Contrast-enhanced transverse CT scan shows several infarcted small-bowel loops (arrows), which manifest with dilatation and air-fluid levels but no wall thickening, due to what?

Answer 39

transmural small-bowel necrosis

Question 40

What is a good study for evaluation of suspected intestinal ischemia but don’t do if planning on percutaneous angiography too (excessive contrast with 2 studies)?

Answer 40

CT angiography

Question 41

What test is better at diagnosing venous occlusions?

Answer 41

MR angiography

Question 42

May need mesenteric percutaneous arteriography. When? 2

Answer 42

1. If the diagnosis is in doubt after non-invasive radiologic evaluation 2. If diagnosis is fairly certain and need consideration for percutaneous treatment or for surgical planning

Question 43

mesenteric percutaneous arteriography cannot be used for what?

Answer 43

Can’t be used for venous occlusions

Question 44

Treatment of acute mesenteric ischemia? | 9

Answer 44

1. Hemodynamic monitoring and support (Correct hypotension, hypovolemia) 2. Correction of metabolic acidosis 3. Broad spectrum antibiotics 4. NG tube for gastric decompression 5. Vasopressors that have less effect on mesenteric perfusion: 6. Anticoagulation unless actively bleeding 7. Correction of arrhythmias 8. Then imaging 9. At angiography can give papaverine directly to relieve mesenteric vasoconstriction 10. If peritoneal signs, may proceed directly to the OR for surgical repair

Question 45

Which vasopressors would you use in treatment? | 3

Answer 45

1. dobutamine, 2. low dose dopamine, 3. milrinone

Question 46

How should imaging proceed?

Answer 46

-May start with plain films or CT, but if strong clinical suspicion should proceed DIRECTLY to angiography

Question 47

If you have peritoneal signs proceed directly to what?

Answer 47

may proceed directly to the OR for surgical repair

Question 48

At angiography can give what to relieve vasoconstriction?

Answer 48

papaverine

Question 49

1. Gold standard diagnostic study for acute arterial ischemia? 2. What is MAE? 3. MAT? 4. MVT?

Answer 49

1. Mesenteric Angiography/Treatment 2. MAE: Surgery & embolectomy; or local infusion of thrombolytic therapy 3. MAT: Surgery w/ thrombectomy + revascularization or heparinization 4. MVT: heparinization + resection of infarcted bowel

Question 50

Nonocclusive mesenteric ischemia: treatment? | 4

Answer 50

1. Papaverine infusion during angiography 2. Reverse underlying conditions 3. Repeat angiography can be done in 24 hrs 4. Surgical exploration reserved for patients with peritoneal signs

Question 51

Overview of the care of these patients | 6

Answer 51

1. Cardiac monitor, 2. venous access, 3. oxygen 4. May require fluid resuscitation 5. Broad-spectrum antibiotics 6. Surgery

Question 52

Chronic mesenteric ischemia 1. Presentation? 2 2. Secondary to what? 3. Strongly associated with what?

Answer 52

1. - Intestinal angina - Episodic or constant intestinal hypoperfusion 2. Secondary to atherosclerosis 3. Strongly associated with meals