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Acute mesenteric ischemia (AMI) is caused by a decrease in blood flow to the intestines such that perfusion no longer meets their metabolic demands.1 This leads to gut ischemia, necrosis, sepsis, and if left untreated, certain death. The incidence of AMI is low; it occurs in 3-5 individuals per 100,000 population and accounts for only 0.09% to 0.2% of all acute admissions to the ED.2 Yet the mortality rate is high and directly correlated to the time to diagnosis and treatment. Thus, a high index of suspicion is required. A delay in diagnosis of more than 24 hours from onset increases mortality from 50% to 70%.3 AMI can be categorized into four types: embolic, thrombotic, nonocclusive mesenteric ischemia (NOMI), or mesenteric venous thrombosis (MVT). Rare causes of AMI include arterial dissection, vasculitis, or aneurysm. Table 37-1 provides a general overview of the four most common types of AMI, while the flow chart in Figure 37-1 depicts the general paradigms for workup and treatment for each respective category, and can be used as a visual guide throughout this chapter.


Work-up and treatment algorithm for AMI, going from left to right. Note alternative pathways for “high suspicion for bowel necrosis” designated with the red text, as compared to “low suspicion for bowel necrosis” as designated with the green text, for each type of mesenteric ischemia. AMI, acute mesenteric ischemia; MVT, mesenteric venous thrombosis; NOMI, nonocclusive mesenteric ischemia; SMA, superior mesenteric artery.

TABLE 37-1

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