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  The classic presentation of mesenteric ischemia is acute abdominal pain that is “out of proportion” to exam.

  
  
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  The majority of patients with mesenteric ischemia have an embolus due to atrial fibrillation.

  
  
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  Morbidity and mortality remains very high despite advances in care, and survival is dependent on early recognition and treatment.

  
  
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  Obtain early surgical consultation if mesenteric ischemia is suspected.

Acute mesenteric ischemia is a syndrome characterized by inadequate blood flow to the mesentery with resultant hypoxemia of the tissue. Over time, the hypoxemia results in tissue break down with loss of bowel integrity.

The incidence of mesenteric ischemia is reported to be 0.1% of hospitalized patients, and this number is thought to be increasing as the average age of the population increases. The mortality is more than 60%. Delay in diagnosis is common, but with reports that early intervention increases survival rate, it is important to always have this diagnosis in the differential for elderly patients presenting with abdominal pain.

Four etiologies of mesenteric ischemia are described, and each has different risk factors and variation in presentation. The most common cause of mesenteric ischemia is arterial emboli (50%), usually owing to atrial fibrillation. Arterial thrombosis at the narrowing of mesenteric arteries in patients with atherosclerosis is responsible for 20% of acute presentations. These patients frequently have other forms of atherosclerosis such as coronary artery disease. Mesenteric venous thrombosis, which may be associated with peripheral deep vein thrombosis, accounts for 5–10% of presentations. Nonocclusive mesenteric ischemia is seen in up to 20–25% of presentations. It is due to low flow states typically seen in shock syndromes. It occurs most commonly in hospitalized patients and is difficult to diagnose.

The mesenteric vessel affected is responsible for the presenting symptoms and area of injury. The superior mesenteric artery (SMA) is the most commonly involved site because of the sharp takeoff of this vessel from the aorta. Approximately 80% of mesenteric blood flow supplies the bowel mucosa, making it the most sensitive to ischemia.

History

Symptoms are nonspecific and common to many conditions. Abdominal pain, nausea, vomiting, and diarrhea are frequently seen. Any patient older than 50 years with risk factors (eg, atrial fibrillation) who experiences acute onset abdominal pain lasting >2 hours should be suspected of having acute mesenteric ischemia. Pain out of proportion to the physical examination is very concerning for mesenteric ischemia. Late findings include peritonitis (eg, pain with movement), fever, weakness, and altered mental status.

Patients with chronic mesenteric ischemia will give a history of “abdominal angina” or pain after eating. This is due to narrowing of the mesenteric artery usually associated with chronic atherosclerosis. With eating there is increased demand for blood flow, causing a relative ischemia until demand is lowered. These patients go on to have thrombotic occlusion of their narrowed vessels, presenting then with the common acute symptoms.