Ischemic Bowel Disease Flashcards
Ischemic Bowel Disease
- Changes how with age?
- Mortality?
- Patterns? 4
- Increases with age
- High mortality, 50~90%
- Patterns:
- small and/or large bowel
- diffuse or localized
- segmental or focal
- superficial or transmural
4 Major causes of Acute Mesenteric Ischemia
- SMA embolism—50%
- SMA thrombosis—15-25%
- Nonocclusive ischemia—20-30%
- Mesenteric venous thrombosis—5%
- SMA thrombosis is often imposed on what?
2. Also occurs with what? 2
- Often superimposed on patients w/ progressive atherosclerotic disease
- Also occurs w/ trauma or infection
Acute mesenteric ischemia
- Occlusive causes? 3
- Non-occlusive causes? 1
- Occlusive
- Mesenteric arterial embolism
- Mesenteric arterial thrombosis
- Mesenteric venous thrombosis - Non-Occlusive
- Hypoperfusion
Circulation to the intestines
1. Primarly through what? 2
- Requires how much of our cardiac output?
- Primarily SMA and IMA
- Lots of collateral circulation - Requires 10-35% of the cardiac output
Regulation of intestinal circulation: In what ways?
5
- Perfusion pressure
- Neural and hormonal mechanisms
- Sympathetic nervous system,
- Renin angiotensin system,
- vasopressin from the pituitary
What does vasopression do for the intestinal vasculature?
2
Vasopressin
- Causes mesenteric (arterial) vasoconstriction and venous dilation
- Reduces portal venous pressure in patients bleeding from portal hypertension
Acute mesenteric ischemia: Hallmarks of clinical presentation
3
- Severe cramping abdominal pain,
- out of proportion of physical findings,
- poorly localized
Acute mesenteric ischemia: Clincial presentation
- Abdominal exam?
- Occult blood sample?
- As bowel ischemia worsens what will happen? 4
- Abdominal exam may be normal initially
- Occult blood in stool
- As bowel ischemia worsens
- Abdominal distention
- Absent bowel sounds
- Peritoneal signs
- +/- feculant odor to the breath
Risk factors associated with acute mesenteric arterial embolism
11
- Advanced age
- Coronary artery disease
- Cardiac valvular disease
- History of dysrhythmias
* *Atrial fibrillation - Post-myocardial infarction mural thrombi
- History of thromboembolic disease
- Aortic surgery
- Aortography
- Coronary angiography
- Aortic dissection
- CHF
Mesenteric arterial embolism
1. What demographic affected mostly?
- What artery does it involve and affects what structure?
- Where?
- Median age: 70, 2/3 are woman
- Superior Mesenteric Artery often involved and affects the jejunum
- 6-8 cm beyond the arterial origin, near middle colic artery
Mesenteric arterial embolism
- Comes from where?
- What also occurs to promote the embolism?
- Clinical presentation? 4
- Prognosis compared to SMA thrombosis?
- Thrombus from L atrium, L ventricle or cardiac valves:
- -Over 20% of cases have emboli multiple - Arteriolar vasoconstriction also occurs
- 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%
- More favorable prognosis than SMA thrombosis
Mesenteric arterial thrombosis usual suspects
4
- Atherosclerotic disease
- Trauma
- Infection
- Does not appear to be associated with a coagulopathy
Mesenteric arterial thrombosis
- Hx of?
- Usual site of blockage is what? 2
- Prognosis?
- When do symptoms develop?
- Usually can elicit a history of chronic mesenteric ischemia
- Usual site of blockage is the
- origin of the SMA or
- celiac axis - Less favorable prognosis
- Symptoms do not develop until significant blockage (collateral circulation) which can complicate revascularization
Mesenteric venous thrombosis
- In what population of ppl?
- Onset?
- Thrombosis of superior mesenteric vein or?
- 30% of the cases involve thrombosis of what?
- Younger population 48~60 y/o
Primary 20%
Secondary 80% - Onset can be acute or develop over the course of a few weeks
- Thrombosis of superior mesenteric vein or
- intestinal strangulation from hernia or volvulus - thrombosis of the portal vein
Mesenteric venous thrombosis:
Longer symptoms presentation
5
Sympotom onset?
- Pain diffuse and nonspecific initially, but later becomes constant
- Anorexia 53-54%
- vomiting 41-77%
- diarrhea 36%, constipation 13-34%
- hematemesis 9-42%
More insidious onset of symptoms
Mesenteric venous thrombosis
risk factors?
9
- Hypercoagulable state (up to 75% have a hypercoagulable disorder)
- Portal hypertension
- Abdominal infections
- Blunt abdominal trauma
- Pancreatitis
- Splenectomy
- Malignancy in portal region
- Personal or family history of DVT or PE
- Dehydration
Intestinal ischemia in mesenteric venous thrombosis pathophysiology
6 steps to the end result?
- Decreased mesenteric venous blood flow
- Results in bowel wall edema (tons of this!!! this is how you know its venous and not arterial)
- Fluid efflux into the bowel lumen
- Results in systemic hypotension & an increase in blood viscosity
- This results in diminished arterial flow
- Leading to submucosal hemorrhage & bowel infarction
- Nonocclusive mesenteric ischemia is a result of what?
- Risk factor?
- Often the pt has what? 2
- Result of splanchnic hypoperfusion & vasoconstriction
- Risk factor—atherosclerotic disease
- Often the patient has a
- life-threatening illness/
- is being treated e.g. CHF, MI, sepsis etc.
Nonocclusive mesenteric ischemia: Pathogenesis
- In general?
- How does this happen? 2
- mesenteric vasospasm
- Homeostatic mechanism maintains cardiac and cerebral blood flow
- Vasopressin & angiotensin involved