Intestinal Ischemia

Raika Jamali M.D.

Gastroenterologist and hepatologist

Sina Hospital

Tehran University of Medical Sciences

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• Arterioocclusive mesenteric ischemia (AOMI)
• Nonocclusive mesenteric ischemia (NOMI)
• Mesenteric venous thrombosis (MVT)
• (hypercoagulable state : protein C or S deficiency, antithrombin III deficiency, polycythemia vera, and carcinoma)
• Strangulated small-bowel obstruction
• Ischemic colitis
• Chronic mesenteric angina

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Risk factors for acute arterial ischemia:�

• Atrial fibrillation
• Recent myocardial infarction
• Valvular heart disease
• Recent cardiac or vascular catheterization

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• The incidence of intestinal ischemia parallels the incidence of atherosclerosis and aging

• Protective responses to prevent intestinal ischemia:

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• Collateralization
• Autoregulation of blood flow
• Increase oxygen extraction from the blood

• Emboli originate from the heart in >75% and lodge distal to the origin of the middle colic artery from the superior mesenteric artery
• Thrombosis of at least two of the major vessels supplying the intestine is required for the development of chronic intestinal angina
• Nonocclusive ischemia is disproportionate mesenteric vasoconstriction in response to a severe physiologic stress (dehydration or shock)

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• If left untreated, early mucosal stress ulceration will progress to full-thickness injury.

Presentation, Evaluation, and Management

• The most significant indicator of survival is the timeliness of diagnosis and treatment
• Acute mesenteric ischemia presents with severe acute abdominal pain out of proportion to the physical findings
• Symptoms: nausea and vomiting, transient diarrhea, and bloody stools
• Early abdominal examination is unimpressive

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• Abdominal distention and hypoactive bowel sounds demonstrate peritonitis
• Complete blood count
• Serum chemistry
• Coagulation profile
• Arterial blood gas
• Amylase
• Lipase
• Lactic acid
• Blood type and cross match
• Cardiac enzymes

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• ECG
• Abdominal radiographs
• CT, and mesenteric angiography
• Mesentery duplex scanning
• Visible light spectroscopy during colonoscopy

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• If the diagnosis of intestinal ischemia is being considered, consultation with a surgical service is necessary

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• Free intraperitoneal air
• Bowel-wall edema (thumbprinting)
• Air within the bowel wall (pneumatosis intestinalis)
• Calcifications of the aorta

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• Dynamic CT with three-dimensional reconstruction is a highly sensitive test for intestinal ischemia.
• In acute embolic disease, mesenteric angiography is best performed intraoperatively
• Duplex imaging serves as a screening test
• Negative duplex scan virtually precludes the diagnosis of mesenteric ischemia
• Endoscopic techniques using visible light spectroscopy can be used in the diagnosis of chronic ischemia.

• The "gold standard" for the diagnosis and management of acute arterial occlusive disease is laparotomy .
• Surgical exploration should not be delayed if:
• Clinical suspicion is high
• Clinical deterioration is present
• Peritonitis is present
• Arteriography and systemic heparinization may assist the vascular surgeon in restoring blood supply to compromised bowel
• In SMA 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.

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• The surgical management of AMI is embolectomy (intraoperative angiography or arteriotomy)
• Although more commonly applied to chronic disease, acute thrombosis may be managed with angioplasty, with or without endovascular stent placement.
• If this is unsuccessful, a bypass from the aorta to the SMA is performed.

• Nonocclusive or vasospastic mesenteric ischemia presents with:
• Generalized abdominal pain
• Anorexia
• Bloody stools
• Abdominal distention

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• patients are obtunded, and physical findings may not assist in the diagnosis

• Markers in support of the diagnosis of advanced intestinal ischemia
• Leukocytosis
• Elevated amylase
• Elevated creatinine phosphokinase levels
• Lactic acidosis
• Investigational markers :
• D-dimer
• Glutathione
• S-transferase
• Platelet-activating factor (PAF)
• Mucosal pH

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• Early manifestations of intestinal ischemia include fluid sequestration within the bowel wall
• Managment
• Nasal O2 and blood transfusions
• Broad-spectrum antibiotics
• Monitoring of the vital signs, urine output, blood gases, lactate levels & abdominal examination
• Vasoconstricting agents should be avoided

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Ischemic colitis

• In ischemic colitis, colonoscopy should be performed to assess the integrity of the colon mucosa
• Severe ischemic colitis (full-thickness bowel-wall necrosis) presents with severe ulcerations
• Follow-up colonoscopy can be performed to rule out progression of ischemic colitis.
• Ischemic colitis is treated with resection of the ischemic bowel and formation of a proximal stoma.
• Primary anastomosis should not be performed in acute intestinal ischemia.

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Nonocclusive mesenteric ischemia

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• Laparotomy is warranted for:
• Signs of peritonitis
• Worsening endoscopic findings
• If the patient's condition does not improve with aggressive resuscitation.

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MVT

• MVT may present with a gradual or sudden onset
• Diagnosis of MVT is made on abdominal spiral CT
• Intravenous contrast will demonstrate a delayed arterial phase and clot within the superior mesenteric vein
• Management
• Optimize hemodynamics
• Intravenous antibiotics
• Anticoagulation
• Compromised bowel is resected.
• Of all acute intestinal disorders, mesenteric venous insufficiency has the best prognosis

Chronic intestinal ischemia

• presents with intestinal angina associated with need for increased blood flow to the intestine.
• Abdominal cramping & pain following ingestion of a meal.
• Weight loss and chronic diarrhea
• Abdominal pain without weight loss is not chronic mesenteric angina.
• Physical examination :
• Abdominal bruit
• Manifestations of atherosclerosis

Diagnosis

• Mesenteric angiography is the Gold standard for confirmation of chronic mesenteric arterial occlusion

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• Magnetic resonance angiography is an alternative if the administration of contrast dye is contraindicated

• Management
• medical management of atherosclerotic disease by:
• Lipid-lowering medications
• Exercise
• Cessation of smoking
• Cardiac evaluation should be performed before intervention
• Endovascular procedures may avoid an operative intervention in selected patients

• After revascularization, the bowel wall should be observed for return of a pink color and peristalsis.
• Palpation of major arterial vessels can be performed as well as applying a doppler flowmeter to the antimesenteric border of the bowel wall, but neither is a definitive indicator of viability.
• In equivocal cases, 1 g of IV sodium fluorescein is administered and the pattern of bowel reperfusion is observed under ultraviolet illumination with a standard (3600 A) Wood's lamp.
• An area of nonfluorescence >5 mm in diameter suggests nonviability.
• If doubt persists, reexploration performed 24–48 h following surgery will allow demarcation of nonviable bowel.
• Primary intestinal anastomosis in patients with ischemic bowel is always worrisome, and reanastomosis should be deferred to the time of second-look laparotomy.