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GI 2 > Ischemic Bowel Dz > Flashcards

Ischemic Bowel Dz Flashcards

1
Q

What are the 4 major causes of acute mesenteric ischemia?

A

Superior Mesenteric artery embolism (50%)

Superior Mesenteric Thrombosis (15-20%)

non-occlusive ischemia (20-30%)

Mesenteric venous thrombosis

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2
Q 
Circulation to the intestines:
-what are the main 2 arteries? 
-regulated by which hormones? 
-innervated by which nerves? 
-
A

2 main arteries SMA and IMA.
*more blood is shunted there after eating.

Regulation:

  • if not adequate perfusion pressure renin and vasopressin come in to improve perfusion.
  • Vasopressin causes mesenteric vasoconstriction and venous dilation, reduces portal venous pressure in patients bleeding from potral HTN.

-innervated by sympathetic nervous system.

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3
Q

Hallmark Clinical Presentation of Ischemic bowel?

Other sx

A

severe cramping, abd pain(worst they’ve ever had) out of proportion of PE findings, poorly localized.
*wont find peritoneal signs, might have bruits.

Sx:

  • sudden or gradual onset
  • prior episode
  • n/v
  • bloody diarrhea
  • as ischemia worsens:
  • -abd distension
  • -absent bowel sounds
  • -peritoneal signs
  • -+/- feculant odor to breath
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4
Q

Risk factors associated with acute mesenteric arterial embolism

A
  • advanced age
  • Coronary artery dz
  • cardiac valvular dz
  • hx of afib
  • aortic surgery
  • aortic dissection
  • CHF
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5
Q

What are the clinical syndromes associated with occlusive and non-occlusive ischemic bowel?

A
  • Occlusive:
  • -mesenteric arterial embolism
  • -mesenteric arterial thrombosis
  • -mesenteric venous thrombosis
  • Non-occlusive:
  • -hypoperfusion
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6
Q

Mesenteric Arterial embolism

  • median age & gender
  • often occludes which artery?
A

median age 70YO and 2/3 are women

Occludes SMA, 6-8cm beyond arterial origin near the middle colic artery and affects the jejunum.

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7
Q

Mesenteric arterial thrombosis

  • etiologies
  • usual site of blockage?
  • sx
A

Etiologies:

  • atherosclerotic dz
  • trauma
  • infection

Usual site of blockage: SMA or celiac axis

Sx:
dont usually develop until significant blockage.
-discomfort so bad that they lose weight b/c they dont want to eat. 15min post prandial they get crampy pain and diarrhea.

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8
Q

Which has a more favorable prognosis, Mesenteric arterial embolus or thrombus?

A

-Mesenteric arterial EMBOLUS has more favorable prognosis.

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9
Q

Mesenteric Venous Thrombosis:

  • MC in which age group
  • onset
  • MC site?
  • sx
A

MC age group 48-60YO

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

MC site: superior mesenteric vein or intestinal strangulation from hernia or volvulus.
*if involves portal vein d/t liver dz.

Sx:

  • insidious onset of sx
  • pain diffuse and nonspecific but later becomes constant
  • anorexia
  • vomiting
  • diarrhea/constipation
  • hematemesis
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10
Q

Mesenteric Venous thrombosis:

  • Risk factors
  • pathophysiology
A

Risk factors:

  • hypercoagulable state*
  • portal HTN*

Pathophysiology:
-decreased mesenteric venous blood flow results in bowel wall edema**, results in systemic hypotension & increase in blood viscosity. This results in diminished arterial flow leading to submucosal hemorrhage and bowel infarction.

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11
Q

Non-occlusive mesenteric ischemia

  • etiology
  • risk factors
  • pathophysiology
  • mortality rate?
  • sx
A

etiology:
- result of splanchnic hypoperfusion & vasoconstriction

Risk factors:
-atherosclerotic dz

HPathophysiology
-mesenteric vasospasm

High mortality; 70%

Sx:

  • progressive abd pain, bloating, n/v, mental status changes(d/t poor perfusion of brain)
  • 25% dont have abd pain
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12
Q

Sx of ischemic colon?

Dx?

A

mild abd pain, tenderness present

rectal bleeding, bloody diarrhea

Dx: colonoscopy
*90% of pts are over age of 60YO

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13
Q

Summary of MC causes of each of the following:

  • Arterial emboli
  • Arterial thrombosis
  • Venous thrombosis
  • Nonocclusive mesenteric ischemia
A

Emboli: atrial fibrillation, MI

Arterial thrombosis: atherosclerotic dz

Venous thrombosis: hypercoagulable, neoplasm

Nonocclusive: low flow states

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14
Q

Work up for bowel ischemia?

A
  • Lab
  • Imaging;
  • -abd xrays
  • -CT of abd***
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15
Q

What may be seen on labs of ischemic bowel dz?

A
  • increased WBC w/ predominance of immature cells
  • increased HCT
  • increased amylase, increased phsophate
  • increased serum lactate
  • metabolic acidosis
  • any pt with abd pain and metabolic acidosis has intestinal ischemia until proven otherwise*
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16
Q

WHat may be seen on plain xrays with ischemic bowel dz?

A
  • pneumotosos intestinalis
  • portal venous gas
  • thickened bowel wall with thumb-printing
  • air fluid levels
  • dilated bowel loops
  • gasless abd
17
Q

Pneumatosis intestinalis:

  • what is this?
  • suggestive of what dz?
A

What: gas cysts in the bowel wall, not gas in the bowel lumen.
*requires surgical removal.

Suggestive of necrotizing enterocolitis.

18
Q

Portal Venous Gas:

  • what is this?
  • cause
A

WHat: accumulation of gas in the portal vein and its branches.

-Cause: ischemic bowel, intra-abd sepsis

19
Q

What is the first step in evaluation of acute abd? What is the next step?

What is the preferred imaging study?

A

Upright and supine plain abd x-rays are the 1st step in eval of acute abd.

CT is the next step if the dx is not made on plain films.

Preferred imaging study is CT.

  • can be with IV and PO contrast.
  • oral contrast necessary for eval of mucosal thickening of the bowel wall.
20
Q

CT findings?

A

Bowel wall thickening: MC in ischemic colitis, colonic infarction, and venous occlusion

Bowel dilation

Fat stranding(fluid in fat, seen on anything causing inflamm) and ascities

Varying degrees of attenuation

Pneumatosis and portomesenteric gas

21
Q

MR angiography:

A

better at dx venous occlusions

22
Q

Tx of Ischemic Bowel

A

Hemodynamic monitoring: correct hypotension, hypovolemia

Cardiac monitor, venous access, O2

  • correction of metabolic acidosis
  • broad spectrum abx
  • NG tube for gastric decompression
  • vasopressors that have less effect on mesenteric perfusion (dobutamine, low dose dopaine, milrinone)
  • anticoagulation unless actively bleeding.
  • correction of arrhythmias
  • THEN imaging
  • -may start with plain films or CT, but if strong suspicion should proceed DIRECTLY to angiography
  • at angiography can give papaverine (anti-spasmodic) directly in to relieve mesenteric vasoconstriction.

-if peritoneal signs may proceed directly to the OR for surgical repair.

23
Q

What is gold standard dx study for acute arterial ischemia?

A

Mesenteric angiography

24
Q

Tx of:

  • Mesenteric aterial embolus
  • mesenteric arterial thrombus
  • Mesenteric venous thrombus
  • nonocclusive mesenteric ischemia
A

MAE: surgery and embolectomy or local infusion of thrombolytic therapy

MAT: surgery w/ thrombectomy + revascularization or heprinization

MVT: heparinization + resection of infarcted bowel.

Non-occlusive mesenteric ischemia:

  • papaverin infusion during angiography
  • reverse underlying conditions
  • repeat angiography can be done in 24hrs
  • surgical exploration reserved for pts w/ peritoneal signs
25
Q

Chronic Mesenteric ischemia

  • sx
  • etiology
  • provoking factor causing sx
A

Sx: intestinal angina, episodic or constant intestinal hypoperfusion

Etiology: 2ndry to atherosclerosis

provoking factor:
Strongly associated with meals

GI 2 (9 decks)

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