Acute mesenteric ischemia
Acute reduction in arterial or venous blood flow to the small intestine; may result in bowel ischemia or infarct
Epidemiology
Etiology
- Acute mesenteric artery embolism
- Most common cause of AMI (causes 50% of all cases)
- Risk factors include atrial fibrillation, myocardial infarction
- Most commonly involves the SMA
- Acute mesenteric artery thrombosis
- Causes ∼ 25% of cases
- Risk factors include visceral atherosclerosis
- Nonocclusive mesenteric ischemia
- Causes ∼ 20% of cases
- Most commonly occurs in critically ill patients with low cardiac output
- Mesenteric venous thrombosis
- Least common cause of AMI (causes < 10% of all cases)
- Risk factors include infection, malignancy, portal hypertension, estrogen therapy, and hypercoagulability disorders.
Pathophysiology
- Sudden interruption of blood flow to small bowel → intestinal hypoxia → hemorrhagic infarction and necrosis → disruption of the mucosal barrier and perforation → release of bacteria, toxins, and vasoactive substances → life-threatening sepsis
- Sites of vessel occlusion
- SMA (∼ 90% of cases)
Clinical features
AMI
- Severe periumbilical pain out of proportion to physical examination
- Diarrhea (bloody in later stages)
Tip
- Patients with acute mesenteric artery embolism typically present with the classic triad of severe abdominal pain, bloody diarrhea, and atrial fibrillation.
- Patients with acute mesenteric artery thrombosis typically have known cardiovascular or peripheral vascular disease and/or symptoms of CMI in addition to acute symptoms.
CMI
- Postprandial abdominal pain: begins 10–30 minutes after eating and lasts 1–2 hours
- Food aversion (sitophobia): fear of eating because of postprandial pain
- Unintended weight loss