Chapter 354 - Mesenteric Vascular Insufficiency

Question 1

What is the incidence of mesenteric ischemia?

Answer 1

2-3 people per 100 000.

Question 2

How can one define the etiology of intestinal ischemia?

Answer 2

“intestinal ischemia is further classified based on etiology, which dictates management: (1) arterioocclusive mesenteric ischemia, (2) nonocclusive mesenteric ischemia, and (3) mesenteric venous thrombosis.”

Question 3

Which conditions might be associated with arterioocclusive mesenteric ischemia?

Answer 3

“Risk factors for arterioocclusive mesenteric ischemia are generally acute in onset and include atrial fibrillation, recent myocardial infarction, valvular hear disease, and recent cardiac or vascular catheterization, all of which result in embolic clots reaching the mesenteric circulation.”

Question 4

What are the causes of nonocclusive mesenteric ischemia?

Answer 4

Intestinal angina, cardiogenic or septic shock, high-dose vasopressor infusion and cocaine overdose. It might also complicate cardiovascular surgery.

Question 5

What is the association between cardiovascular surgery and gastrointestinal ischemia? How frequent is this association?

Answer 5

“Nonocclusive mesenteric ischemia is the most prevalent gastrointestinal disease complicating cardiovascular surgery. The incidence of ischemic colitis following elective aortic repair is 5-9% and the incidence triples in patients following emergent repair.”

Question 6

Name two colonic points susceptible to ischemia and explain the reason why it is so.

Answer 6

“Collateral vessel within the colon meet at the splenic flexure and descending/sigmoid colon. These areas, which are inherently at risk for decreased blood flow, are known as Griffith’ point and Sudeck’s point, respectively, and are the most common locations for colonic ischemia.”

Question 7

The splenic flexure might receive more percentage of cardiac output than the kidneys.
True or False?

Answer 7

True.

The splenic flexure can receive up to 30% of the cardiac output, in comparison to 20-25% of renal vascular flow.

Question 8

What is the most frequent origin of intestinal embolization? Where does it embolize to more frequently?

Answer 8

“Emboli originate from the heart in more than 75% of cases and lodge preferentially in the superior mesenteric artery just distal to the origin of the middle colic artery.”

Question 9

Even in the early phases of intestinal ischemia, there might be bacteremia due to translocation of bacteria across the intestinal mucosa.
True or False?

Answer 9

True.

Question 10

How high is the mortality associated with intestinal ischemia?

Answer 10

> 50%

Question 11

What are the main symptoms of acute intestinal ischemia?

Answer 11

“severe acute, nonremitting abdominal pain strikingly out of proportion to the physical findings. Associated symptoms may include nausea and vomiting, transient diarrhea, anorexia, and bloody stools.”

Question 12

Which findings might occur in early and late acute intestinal ischemia?

Answer 12

“With the exception of minimal abdominal distension and hypoactive bowel sounds, early abdominal examination is unimpressive. Later findings will demonstrate peritonitis and cardiovascular collapse.”

Question 13

What would you look for in an abdominal radiography if you suspected of intestinal ischemia?

Answer 13

“A plain abdominal film may show evidence of free intraperitoneal air, indicating a perforated viscs and the need for emergent exploration. Earlier features of intestinal ischemia seen on abdominal radiographs include bowel-wall edema, known as “thumbprinting.” If the ischemia progresses, air can be seen within the bowell wall (pneumatosis intestinalis) and within the portal venous system. Other features include calcifications of the aorta and its tributaries, indicating athersclerotic disease.”

Question 14

What is the greatest limitation of duplex imaging?

Answer 14

Body habitus (obesity for example).

Question 15

The key to early diagnosis of arterial embolus as the cause of arterioocclusive mesenteric ischemia is mesenteric angiography.
True or False?

Answer 15

False.

Early laparotomy.

Question 16

Mesenteric duplex with a high peak velocity of flow in the superior mesenteric artery is associated with an approximately 80% positive predictive value of mesenteric ischemia. This is the significant use of this technique.
True or False?

Answer 16

False.
While the predictive valor is indeed 80%, “More significantly, a negative duplex scan virtually precludes the diagnosis of mesenteric ischemia.”

Question 17

You have the suspicion that a patient has chronic intestinal ischemia. Mesenteric angiography is not an option since the patient has severe chronic renal insufficiency. Which technique might be useful?

Answer 17

Colonoscopy (evaluation of the splenic flexure).

Question 18

Which indicators are important in arterioocclusive mesenteric ischemia that require surgical exploration?

Answer 18

“Surgical exploration should not be delayed if suspicion of acute occlusive mesenteric ischemia is high or evidence of clinical deterioration or frank peritonitis is present.”

Question 19

The small-intestine becomes ischemic while the colon is spared in the occlusion of the superior mesenteric artery.
True or False?

Answer 19

False.
“In the case of superior mesenteric artery occlusion where the embolus usually lies just proximal to the origin of the middle colic artery, the proximal jejunum is often spared while the remainder of the small bowel to the transverse colon will be ischemic.”

Question 20

Name investigational markers for intestinal ischemia.

Answer 20

D-dimer, glutathione S-transferase, platelet-activating factor and mucosal pH monitoring.

Question 21

What is the most important intervention to maintain hemodynamics in intestinal ischemia and which one is to be avoided?

Answer 21

Fluid resuscitation and vasoconstricting agents, respectively.

Question 22

Which ischemic etiology most frequently involves the rectosigmoid region?

Answer 22

Nonocclusive mesenteric ischemia (inferior mesenteric artery).

Question 23

How does one classify the intestinal ischemia macroscopically (colonoscopy)?

Answer 23

“Ischemia of the colonic mucosa is graded as mild with minimal mucosal erythema or as moderate with pale mucosal ulcerations and evidence of extensions to the muscular layer of the bowel wall. Severe ischemic colitis presents with severe ulcerations resulting in black or green discoloration of the mucosa, consistent with full-thickness bowell-wall necrosis.”

Question 24

How reversible is ischemia depending on its classification?

Answer 24

Mild ischemia: almost 100% reversible
Moderate ischemia: approximately 50% reversible
Severe ischemia: irreversible

Question 25

True or False?

(1) Nonocclusive mesenteric ischemia due to vasospasm is documented by the use of angiography
(2) Nonocclusive mesenteric ischemia due to hypoperfusion is documented with spiral CT or colonoscopy
(3) Colonoscopy is not indicated in vasospastic disease
(4) Primary anastomisis of the colon after resection of the affected bowel is indicated

Answer 25

(1) True
(2) True
(3) False, it is especially indicated in patients who cannot undergo contrast for angiography. Colonoscopy is an excellent diagnostic tool in this instance.
(4) False, “Primary intestinal anastomosis in patients with ischemic bowel is always worrisome; thus, delayed bowel reconstruction and renastomosis should be deferred to the time of second-look laparotomy.”

Question 26

Antibiotic prohylaxis is indicated in all causes of intestinal ischemia.
True or False?

Answer 26

True.

Question 27

Venous thrombosis has a better prognosis than arterial mechanisms of intestinal ischemia.
True or False?

Answer 27

True.

Question 28

Chronic intestinal ischemia might present with abdominal pain wihouth weight loss.
True or False?

Answer 28

False.

Question 29

What is the gold standard test to identify mesenteric arterial occlusion?

Answer 29

Angiography.

Question 30

How high is the percentage of success of angioplasty with endovascular stenting in chronic mesenteric ischemia?

Answer 30

80% long-term

Question 31

How does one determine the intra-operatory success of revascularization?

Answer 31

“Determination of intestinal viability intraoperatively in patients with suspected intestinal ischemia can be challenging. After revascularization, the bowel wall should be observed for return of a pink color and peristalsis. Palpation of major arterial mesenteric vessels can be performed, as well as applying a Doppler flowmeter to the antimesenteric border of the bowell wall, but neither is a definitive indicator of viability. In equivocal cases, 1g of IV sodium fluorescein is admininistered, and the pattern of bowel reperfusion is observed under ultraviolet ilumination with a standard (3600 A) Wood’s lamp. An area of nonfluorescence >5mm in diameter suggests nonviability. If doubt persists, reexploration performed 24-48h following surgery will allow dermacation of nonviable bowel.”