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Classically, in acute mesenteric ischemia, the patient has severe generalized abdominal pain out of proportion to the abdominal exam; hyperactive bowel sounds may be present initially (i.e., peritoneal signs are usually absent), nausea, vomiting, and diarrhea occur. There may be leukocytosis. If not recognized early, bowel ischemia worsens. Signs such as fever, metabolic acidosis, leukocytosis, bloody diarrhea, peritoneal signs, hypovolemia, and septic shock may occur. The clinician needs to have a high suspicion for this diagnosis as there is a high mortality rate. Causes include but are not limited to embolism secondary to dysrhythmias (especially in the elderly with atrial fibrillation), thrombosis due to low-flow states (sepsis, cardiogenic shock, congestive heart failure [CHF], and hypovolemia), hypercoagulable disorders, drugs causing mesenteric vasoconstriction (vasopressors), and by penetrating or blunt trauma (e.g., seat-belt trauma).

• Diagnostic modalities include CT angiography to assess the vasculature and bowel for evidence of ischemia, perforation, or free air, and early angiography if indicated. Plain abdominal films may demonstrate an ileus but can be normal in up to 25% of patients with acute ischemia. They are useful in excluding perforation and obstruction. Treatment includes emergency laparotomy, visceral bypass, embolectomy, resection of the ischemic bowel, fluid resuscitation, and anticoagulation.