There are four causes of acute mesenteric ischemia: arterial embolus, arterial thrombosis, mesenteric venous thrombosis, and nonocclusive mesenteric ischemia.
History, physical exam, and laboratory findings lack the sensitivity and specificity to exclude acute mesenteric ischemia. CT angiography can rapidly and accurately confirm the diagnosis.
Survival is associated with rapid diagnosis and surgical treatment, which involves restoring perfusion and removing necrotic bowel.
Advances in imaging, operative techniques, and critical care have led to a steady decline in overall mortality.
“As occlusion of the mesenteric vessels is usually associated with heart-disease or atheromatous arteries or cirrhosis of the liver, we must not expect much from operative treatment.”
J.W. Elliot 1895
For more than a century since Elliot’s description of two patients operated on at the Massachusetts General Hospital for “gangrene of the intestine,” the diagnosis and treatment of acute mesenteric ischemia (AMI) have challenged even the most astute clinicians.1,2 The vague, nonspecific symptoms of AMI overlap with common illnesses, which results in diagnostic delays that historically led to abysmal outcomes.3–5 As a disease primarily affecting the elderly with multiple comorbidities, the mortality of AMI exceeds 50% in recent series, even with early diagnosis.6–8 While societal aging has not led to an exponential rise in the incidence of AMI, thanks in part to lifestyle changes,9 physicians must still maintain a high index of suspicion. Thorough understanding of the presentation, diagnosis, and treatment of AMI is necessary, especially considering that AMI occurs more commonly than appendicitis in those over 75 years of age.10,11 This chapter reviews the most common causes of AMI: arterial embolism (AE), arterial thrombosis (AT), mesenteric venous thrombosis (MVT), and nonobstructive mesenteric ischemia (NOMI). Other causes of bowel necrosis such as volvulus, hernias, or obstruction will not be discussed, although these represent important pathologic considerations.
EPIDEMIOLOGY AND COMORBIDITIES ASSOCIATED WITH AMI
The rates of AMI vary significantly depending on the origin of the report, but the condition occurs more frequently than expected.9 An autopsy study from Harvard in 1967 noted an AMI incidence of 88/100,000 patient-years.12 In their study from Malmö, Sweden, Acosta and colleagues noted a 12.9/100,000 patient-year incidence of AMI, which was more than double the rate of ruptured abdominal aortic aneurysm (5.5/100,000).13 While AMI is a disease of the elderly, the incidence appears to be declining despite the aging population. A recent study utilizing the National Inpatient Sample registry showed that the incidence of AMI decreased from 8.4/100,000 to 6.7/100,000 patient-years between 1995 and 2010, respectively.9 A 1993 study from San Francisco reported an incidence of 1/1000 admissions,14 but the rate in Japan in 2009 reported at ∼0.1/1000 admissions.10 This decrease in incidence may be reflective of changing lifestyles (decreased tobacco use) and disease modification through statins and anticoagulation.9 The etiology of AMI varies ...