What is Acute Mesenteric Ischemia (AMI)?
Acute mesenteric ischemia (AMI) is a life-threatening surgical emergency caused by sudden interruption of blood supply to the intestine, leading to cellular damage, intestinal necrosis, and death if untreated, with mortality rates consistently exceeding 50%. 1
Definition and Pathophysiology
AMI represents a group of diseases characterized by an interruption of blood supply to varying portions of the intestine, resulting in ischemia and secondary inflammatory changes that progress to life-threatening intestinal necrosis without treatment. 1
The condition occurs when blood flow to the intestine is suddenly compromised, causing:
- Cellular ischemia and damage 1
- Progressive inflammatory changes 1
- Intestinal necrosis if blood flow is not restored 1
- Overwhelming systemic inflammatory response and death 2
Epidemiology
AMI is uncommon but deadly, accounting for only 0.09-0.2% of all acute surgical admissions, yet carries mortality rates of 50-80% despite modern treatment advances. 1, 3
Key epidemiologic features include:
- Incidence increases significantly with age 1
- Represents an infrequent cause of abdominal pain but a common cause of emergent intestinal resection 1
- More than 20% of superior mesenteric artery emboli are associated with concurrent emboli to other arterial beds 1
Etiologic Classification
AMI is classified as either occlusive or non-occlusive (NOMI), with specific etiologies having distinct frequencies: 1
Occlusive Types:
- Mesenteric arterial embolism (50% of cases) - Most common etiology, typically originating from cardiac sources including atrial fibrillation, left ventricular dysfunction with poor ejection fraction, or cardiac valves due to endocarditis 1
- Mesenteric arterial thrombosis (15-25%) - Usually occurs in patients with pre-existing atherosclerotic disease 1
- Mesenteric venous thrombosis (5-15%) - Affects younger patients with hypercoagulable states 1, 4
Non-Occlusive:
- Non-occlusive mesenteric ischemia (NOMI) - Results from mesenteric vasoconstriction in low-flow states, typically associated with cardiac dysfunction and vasopressor use 1, 5
Clinical Significance
The critical importance of AMI lies in its extremely high mortality when diagnosis is delayed, making early recognition and prompt intervention the cornerstones of survival. 1, 3
Why AMI Matters:
- Mortality remains 50-80% if untreated despite advances in diagnostic and treatment modalities 3
- Time to diagnosis and intervention is the most critical determinant of survival 3, 5
- Delayed diagnosis is the single most significant contributor to high mortality 3
- Early intervention can reverse the ischemic process and lead to full recovery, but once intestinal necrosis develops, outcomes are catastrophic 2
Diagnostic Challenges:
- Symptoms are nonspecific, making early diagnosis extremely difficult 3, 5
- Classic presentation is sudden onset of severe abdominal pain that is disproportionate to physical examination findings 4
- Laboratory findings are of limited diagnostic value in early disease 3
- Radiographic findings typically appear late, when bowel infarction has already occurred 3
Modern Management Paradigm
CT angiography is the first-line diagnostic tool, and endovascular approaches have emerged as preferred initial treatment for patients without peritonitis, showing improved outcomes compared to traditional open surgery. 5
The World Society of Emergency Surgery emphasizes that a focused multidisciplinary approach based on early diagnosis and individualized treatment is essential, incorporating: 1