A 75-year-old man in the ICU with septic shock and on high-dose vasopressors develops acute abdominal pain with distension and bloody diarrhea. CT angiography shows patent mesenteric arteries but diffuse small bowel wall thickening. The most likely mechanism of this condition is:
- A Embolic occlusion of the superior mesenteric artery
- B Mesenteric venous thrombosis from hypercoagulability
- C Splanchnic vasoconstriction due to reduced cardiac output ✓
- D Atherosclerotic plaque rupture at the SMA origin
Correct answer: C. Splanchnic vasoconstriction due to reduced cardiac output
Explanation
Non-occlusive mesenteric ischemia (NOMI) accounts for 20-30% of acute mesenteric ischemia cases. It results from splanchnic vasoconstriction as a compensatory response to reduced cardiac output, commonly in critically ill patients on vasopressors. The hallmark is bowel ischemia without mechanical occlusion of mesenteric arteries. Mortality remains high (50-70%).
Reference: Sabiston Textbook of Surgery, 21st ed.
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