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Mesenteric Ischemia
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Related narrative: Non-Occlusive Mesenteric Ischemia Risk Factors and Clinical Presentation Mesenteric ischemia is a narrowing or blockage of one or more of the three arteries that supply the large and small intestines. It is most often an acute finding, but can also be chronic in nature-frequently when associated with multiple mesenteric vessels. Mortality rates for acute mesenteric ischemia are high-they average 71% and the literature ranges from 59-93%. Early diagnosis-before bowel infarction-improves survival rates. Nonocclusive mesenteric ischemia comprises about 20% to 30% of acute mesenteric ischemia cases, and usually is due to splanchnic vasoconstriction. Mesenteric ischemia is often seen in patients with atherosclerotic arterial disease elsewhere, such as patients with coronary artery disease, or peripheral vascular disease. Acute mesenteric ischemia can be caused by an embolus that has traveled from the heart or aorta to block one of the mesenteric arteries-usually the superior mesenteric artery because of the flow dynamics from the aorta. This type of embolus is more commonly seen in patients with heart arrhythmias, like atrial fibrillation, where the embolus is broken off the mural thrombus when the rhythm converts to sinus. It is more common in smokers and in patients with elevated serum cholesterol levels. Other risk factors include age greater than 50 years with congestive heart failure, cardiac arrhythmias, recent myocardial infarction, hypovolemia, hypotension, or sepsis. Nonocclusive mesenteric ischemia has been associated with cardiac surgery and dialysis. Acute mesenteric ischemia causes sudden and severe abdominal pain, diarrhea, and vomiting; however, pain is absent in as many as 25% of patients with nonocclusive mesenteric ischemia. The pain is severe and out of proportion to the physical findings; the abdomen is usually not tender in the beginning. In these cases, abdominal distention or gastrointestinal bleeding may be the only symptoms until the condition progresses. Chronic mesenteric ischemia (or mesenteric angina) usually causes pain after eating and occasionally, diarrhea. Diagnosis and Treatment Mesenteric angiography is considered the gold standard for diagnosis of acute mesenteric ischemia. This is the best way to determine if a mesenteric ischemia is occlusive or nonocclusive. Computed tomography is another method used in diagnosing occlusive mesenteric ischemia. Plain-film x-ray can sometimes be helpful in diagnosis if the inferior mesenteric is involved, and there is mucosal edema, but it is more often used to rule out other causes of abdominal pain. X-ray can also detect "thumbprinting" from submucosal hemorrhaging. If the mesenteric ischemia is nonocclusive, the treatment is the infusion of a vasodilator-usually papaverine hydrochloride-into the superior mesenteric artery. Infusion is maintained until there is no evidence of vasoconstriction. Limited data using this approach show that the mortality rate can be reduced to 0-55%. Patients with peritoneal signs are usually treated surgically, because these signs indicate that a loop of bowel is dying and causing inflammation of the peritoneal surfaces. Diffuse peritonitis indicates that the necrotic segment has perforated and spilled its contents. In the case of nonocclusive mesenteric ischemia, anticoagulation treatment with heparin or Coumadin is indicated, but there is controversy as to when it should be initiated-either immediately or after a 48-hour delay because of the risk of internal bleeding from the bowel. Data supporting either approach are limited. Treatments for occlusive mesenteric ischemia vary depending on the diagnosis, but may include surgical revascularization, embolectomy, resection of infarcted bowel, intra-arterial perfusion with a thrombolytic agent, intra-arterial infusion of vasodilators, and simple systemic anticoagulation. References: Brandt LJ. AGA technical review on intestinal ischemia. Gastroenterology 2000; 118(5):954-68. Brandt LJ, Smithline AE. Ischemic lesions of the bowel. In: Sleisenger & Fordtran's Gastrointestinal and Liver Disease, 6th ed. Vol 1, Feldman, M (ed). 1998; Philadelphia: W. B. Saunders Company. Greenwald DA, Brandt LJ, Reinus JF. Ischemic bowel disease in the elderly. Gastroenterology Clinics of North America 2001; 30(2):445-473. Lock G, Scholmerich J. Non-occlusive mesenteric ischemia. Hepatogastroenterology 1995; 42:234-239.
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