Mesenteric ischemia


Acute mesenteric ischemia is a rare event.

Accounts for 1 in every thousand hospital admissions.

Associated with a mortality rate depending etiology of 30-90%.

Four types of acute mesentery ischemia: acute superior mesenteric artery thromboembolism, mesenteric arterial thrombosis, mesenteric venous thrombosis, and nonocclusive mesenteric ischemic disease.


Mesenteric ischemia (MI) is about ischemia of the small bowel. 



Mesenteric ischemia refers to is a medical condition in which injury to the small intestine occurs due an impaired blood supply.



Risk factors for acute mesenteric ischemia include atrial fibrillation, heart failure, chronic kidney failure, previous myocardial infarction and  chronic disease. 



Most people affected are over 60 years old, and both genders are equally affected.



If it comes on suddenly, it is known as acute mesenteric ischemia, or gradually, known as chronic mesenteric ischemia.



Acute mesenteric ischemia often presents with sudden severe abdominal pain and is associated with a high risk of death.



Acute mesenteric ischemia affects about five per hundred thousand people per year.



The chronic mesenteric ischemia typically presents more gradually with abdominal pain after eating, unintentional weight loss, vomiting, and fear of eating.



Chronic mesenteric ischemia affects about one per hundred thousand people.



Symptoms of acute MI: sudden and severe abdominal pain.



Symptoms of chronic  MI: abdominal pain after eating, unintentional weight loss, vomiting.



Usual onset of MI  is 60 years or older.old



Frequency of acute MI 5 per 100,000 per year in developed world and 1 per 100,000 for chronic MI.



Mechanisms  by which poor blood flow occurs: thromboembolism from elsewhere lodging in an artery, a new blood clot forming in an artery, a blood clot in the superior mesenteric vein, and insufficient blood flow due to low blood pressure or arterial spasm.



Diagnosis: best method is angiography, with computed tomography (CT) being used when that is not available.



Treatment of acute ischemia: included stenting or medications to break down the clot at the site of obstruction by interventional radiology.



Open surgery may remove or bypass the obstruction and may be required to remove any intestines that have undergone necrosis.



Outcomes are often poor with treatment the risk of death is 70% to 90%.



With chronic  mesenteric ischemia bypass surgery is the treatment of choice.



Thrombosis of the vein may be treated with anticoagulation, and with surgery used if they do not improve.



Three phases of MI redistribution.



A hyperactive stage occurs first:


primary symptoms are severe abdominal pain and the passage of bloody stools. 



Many patients in the hyperactive phase get better and do not progress beyond this phase.



A paralytic phase can follow: the abdominal pain becomes more widespread, the abdomen  becomes more tender, and bowel motility decreases, resulting in abdominal bloating, no further bloody stools, and absent bowel sounds on exam.



The final shock phase can develop as fluids start to leak through the damaged colon lining, with associated shock and metabolic acidosis, dehydration, hypotension, tachycardia and confusion. 



Clinically symptoms can be acute, subacute, or chronic.



Diagnosis suspected: 



Development of  severe and persisting abdominal pain that is disproportionate to abdominal findings.



Mesenteric arterial thrombosis or embolism is associated with symptoms that are relative mild in 50% of cases for three to four days before being brought to medical attention.



A patient with an arrhythmia such as atrial fibrillation that is complaining of abdominal pain is highly suspected of having embolization to the superior mesenteric artery until proved otherwise.



It is difficult to diagnose mesenteric ischemia early.



Leukocytosis is common



Lactic acid elevation is common



A number of devices have been used to assess the sufficiency of oxygen delivery to the colon during endoscopy.



Findings on gastroscopy may include edematous gastric mucosa,and hyperperistalsis.



Finding on colonoscopy may include: fragile mucosa, erythema, ulcers, and loss of haustrations.



Plain abdominal X-rays are often normal or show non-specific findings.



Abdominal computed tomography is often used for diagnosis, and its accuracy depends on whether a small bowel obstruction is present or absent.



Findings on abdominal CT scan include:



Mesenteric edema



Bowel dilatation



Bowel wall thickening



Mesenteric stranding



Findings of adjacent solid organ infarctions to the kidney or spleen, that are consistent with a cardiac embolic shower phenomenon.



In embolic acute mesenteric ischemia, CT-Angiography can reveal the emboli itself lodged in the superior mesenteric artery, as well as the presence or absence of distal mesenteric branches. 



Late mesenteric findings of dead bowel, include:



Intramural bowel gas



Portal venous gas



Free abdominal air



Mesenteric angiography can differentiate the cause of mesenteric ischemia: embolic or thrombotic occlusion of the mesenteric vessels or nonocclusive ischemia.



Angiography provides the possibility of direct infusion of vasodilators in the setting of thrombotic ischemia.



The treatment of mesenteric ischemia if bowel has become necrotic, the only treatment is surgical removal of the dead segments of bowel.



In non-occlusive mesenteric ischemia, without blockage of the arteries supplying the bowel, the treatment is medical rather than surgical. 



Patients require hospitalization, for intravenous fluids, and optimization of their cardiovascular function.



NG tube decompression and heparin anticoagulation may also be used to optimize perfusion.



Surgical revascularisation is the treatment of choice for mesenteric ischaemia related to an occlusion of the vessels supplying the bowel.



Thrombolytic treatment and vascular interventional radiological techniques have a growing role in management of mesenteric ischemia.



Gangrenous bowel requires resection.



The prognosis depends on prompt diagnosis, before gangrene, and underlying cause: 


venous thrombosis: 32% mortality, 



arterial embolism: 54% mortality, 



arterial thrombosis: 77% mortality, 



non-occlusive ischemia: 73% mortality.



With prompt diagnosis and therapy, acute mesenteric ischemia can be reversible.



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