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
Nonocclusive mesenteric ischemia
- Mortality?
- Severity and location of pain may be different than occlusive mesenteric ischemia. Presentation? 4
- high mortality -up to 70%
- Progressive abdominal pain,
- bloating,
- N/V,
- mental status changes
Up to 25% of patients do not have abdominal pain
What if the ischemia is in the colon?
- 90% of pts are of what age?
- How do patients appear?
- Presentation? 4
- Dx?
- 90 percent of patients over age 60 years
- Acute precipitating cause is rare
- Patients do not appear severely ill
- Mild abdominal pain,
- tenderness present
- Rectal bleeding,
- bloody diarrhea typical
- Colonoscopy is procedure of choice
Summary of the etiology of acute mesenteric ischemia
- Aterial emboli? 2
- Arterial thrombosis? 1
- Venus thrombosis? 2
- Nonocclusive mesenteric flow? 1
- Arterial emboli:
- Atrial fibrillation,
- MI - Arterial thrombosis:
- Atherosclerotic disease - Venous thrombosis:
- Underlying disorder in coagulation (hypercoagulable),
- neoplasm - Nonocculsive mesenteric ischemia:
- Low flow states
Acute mesenteric ischemia workup?
2
- Lab
2. Imaging
Which labs for Acute mesenteric ischemia ?
5
- ↑WBCs with predominance of immature cells
- ↑HCT (hemoconcentration)
- ↑Amylase (50%), ↑phosphate (80%)
- ↑Serum lactate
- -77-100% sensitivity/42% specificity - Metabolic acidosis
Which imaging tests for Acute mesenteric ischemia?
2
- Plain abdominal x-rays
2. CT scan of the abdomen
Any patient with 1._____________ and 2._____________ has intestinal ischemia until proven otherwise
- abdominal pain
2. metabolic acidosis
Imaging – Plain X-rays will show?
6
- Pneumatosis intestinalis
- Portal venous gas
- Thickened bowel wall with thumb-printing
- Air fluid levels
- Dilated bowel loops
- Gasless abdomen
In cases of surgically proven acute mesenteric ischemia:
what will you find on the XRAY? 5
- Air fluid levels 67%,
- Dilated bowel loops 18%,
- Gasless abdomen 10%,
- Pneumatosis 2%,
- Portal venous gas 2%
- What is Pneumatosis intestinalis?
2. Suggestive of what?
- Gas cysts in the bowel wall
(It is not gas in the bowel lumen) - Suggestive of necrotizing enterocolitis
- Portal venous gas is what?
2. A variety of causes such as what? 2
- Accumulation of gas in the portal vein and it’s branches
- A variety of causes such as
- ischemic bowel,
- intra-abdominal sepsis
What are the first step in evaluation of the acute abdomen?
Upright and supine plain abdominal x-rays
What will you see on xrays that are suggestive of bowel ischemia?
5
- Free air,
- obstruction,
- ileus,
- intussusception,
- volvulus
Mesenteric ischemia is difficult to diagnose on plain films alone
What is the next step if the dx is not made on plain films?
CT
CT is the preferred imaging study: appearance will vary based on what?
7
- Cause
- Severity
- Localization
- Extent and distribution
- Presence and degree of submucosal or intramural hemorrhage,
- superimposed bowel wall infection, or
- bowel wall perforation
- CT with or without contrast?
2. What about if ordering a CT angiogram?
- Oral and IV contrast
Oral contrast necessary for evaluation of the mucosal thickening of the bowel wall - If just ordering a CT angiogram (CTA) may not want to have oral contrast because it can obscure the view of the mesenteric vessels
CT findings
5
- Bowel wall thickening
- Bowel dilation (can be assoc. with wall thinning)
- Fat stranding and ascites
- Varying degrees of attenuation
- High attenuation (white)
- Low attenuation (black) - Pneumatosis and portomesenteric gas
What is the most common finding in ischemic colitis, colonic infarction, and venous occlusion?
Bowel wall thickening
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?
transmural small-bowel necrosis
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)?
CT angiography
What test is better at diagnosing venous occlusions?
MR angiography
May need mesenteric percutaneous arteriography. When? 2
- If the diagnosis is in doubt after non-invasive radiologic evaluation
- If diagnosis is fairly certain and need consideration for percutaneous treatment or for surgical planning
mesenteric percutaneous arteriography cannot be used for what?
Can’t be used for venous occlusions
Treatment of acute mesenteric ischemia?
9
- Hemodynamic monitoring and support (Correct hypotension, hypovolemia)
- Correction of metabolic acidosis
- Broad spectrum antibiotics
- NG tube for gastric decompression
- Vasopressors that have less effect on mesenteric perfusion:
- Anticoagulation unless actively bleeding
- Correction of arrhythmias
- Then imaging
- At angiography can give papaverine directly to relieve mesenteric vasoconstriction
- If peritoneal signs, may proceed directly to the OR for surgical repair
Which vasopressors would you use in treatment?
3
- dobutamine,
- low dose dopamine,
- milrinone
How should imaging proceed?
-May start with plain films or CT, but if strong clinical suspicion should proceed DIRECTLY to angiography
If you have peritoneal signs proceed directly to what?
may proceed directly to the OR for surgical repair
At angiography can give what to relieve vasoconstriction?
papaverine
- Gold standard diagnostic study for acute arterial ischemia?
- What is MAE?
- MAT?
- MVT?
- Mesenteric Angiography/Treatment
- MAE: Surgery & embolectomy; or local infusion of thrombolytic therapy
- MAT: Surgery w/ thrombectomy + revascularization or heparinization
- MVT: heparinization + resection of infarcted bowel
Nonocclusive mesenteric ischemia: treatment?
4
- Papaverine infusion during angiography
- Reverse underlying conditions
- Repeat angiography can be done in 24 hrs
- Surgical exploration reserved for patients with peritoneal signs
Overview of the care of these patients
6
- Cardiac monitor,
- venous access,
- oxygen
- May require fluid resuscitation
- Broad-spectrum antibiotics
- Surgery
Chronic mesenteric ischemia
- Presentation? 2
- Secondary to what?
- Strongly associated with what?
- Intestinal angina
- Episodic or constant intestinal hypoperfusion
- Secondary to atherosclerosis
- Strongly associated with meals
