creation date: 2026-04-03 20:59
tags: Pathologies
Acute Mesenteric Ischemia
Background
Definitions
Acute mesenteric ischemia is characterized by a sudden loss of blood flow through the mesenteric vessels and subsequent hypoperfusion of the intestines. Without treatment, this condition can rapidly deteriorate and is life-threatening.
Occlusive mesenteric arterial ischemia refers to ischemia due to thromboembolism or thrombosis.
Non-occulsive mesenteric ischemic refers to non-thrombotic/embolic causes.
Etiology
Embolic causes
- Peripheral arterial emboli
- Cardiac emboli (most common)
- Atheromatous plaque rupture/dislodgement
Thrombotic causes
- Atheromatous vascular disease (eg. atherosclerosis, aortic aneurysm, aortic dissection)
- Decreased cardiac output due to secondary cause
Non-occlusive causes
- Drugs that reduce blood flow (eg. vasopressors and ergotamines)
- Hypotension due to secondary cause
- Recent major surgery
Pathophysiology
Emboli primarily affects the superior mesenteric artery (SMA) due to the narrowing and angle of the artery. The IMA is unlikely to be affected due to its smaller caliber.
The middle section of the jejunum is most often involved as it is furthest from collateral circulation from the celiac and inferior mesenteric arteries.
Thrombosis most typically occur due to pre-existing atherosclerotic disease. However, vascular injury may also cause thrombosis. In most cases, acute thrombosis occurs in the setting of chronic mesenteric ischemia from progressive atherosclerosis (termed acute-on-chronic ischemia). In this case, an inciting factor such as dehydration over arterial stenosis results in acute symptoms.
It should be noted that multiple major mesenteric arteries needs to be affected generally for significant symptoms due to the development of collateral circulation from chronic ischemia.
In cases of non-occlusive causes, vasospasm of the SMA is common secondary to hypoperfusion.
Clinical Presentation
Signs & Symptoms
Signs and symptoms are often non-specific early on. Findings may include:
- Acute onset abdominal pain (analogous to “abdominal angina”)
- Minimal finding on examination (“pain out of proportion”)
- Metabolic acidosis
Other associated symptoms include:
- Bowel emptying
- Nausea/vomiting
- Bloody stool (uncommon unless advanced ischemia)
History & Physical Exam
Assessment includes presence of risk factors.
Risk Factors
Risk of embolism:
- Cardiac arrhythmias and valvular disease
- Infective endocarditis
- Recent MI
- Ventricular aneurysm
- Cardiac surgery
- Cardiopulmonary bypass
- Cardiogenic shock
- Intra-aortic balloon pump placement
- Aortic atherosclerosis
- Aortic aneurysm
Risk of thrombosis:
- Atherosclerotic burden (coronary artery, cerebrovascular, peripheral artery disease)
- Advanced age
- Low cardiac output states
Diagnosis
Criteria
In patients with advanced ischemia (bowel perforation, peritonitis) and hemodynamic instability, diagnosis is made in the operating room. A presumptive diagnosis is typically made based on known risk factors and history.
In cases where immediate surgery is not indicated, diagnosis is made by demonstration of occlusion within mesenteric arteries on imaging studies.
- High-resolution CT-angiography (without oral contrast)
CT Findings
Embolic mesenteric occlusion
- Oval-shaped thrombus surrounded by contrast in noncalcified arterial segment
- Found in middle and distal portion of proximal SMA
Thrombotic mesenteric occlusion
- Thrombus superimposed on heavily calcified occlusive lesion
- Found at ostium of the SMA
- May have variable distribution if associated with hypercoagulable states
Work-up
Investigations apart from diagnostic CT are generally not useful diagnostically but may be helpful in identifying complications. Routine investigation for abdominal pathology are:
- CBC (classically: leukocytosis)
- ABG (classically: acidosis)
- Lactate (classically: elevated)
Differential
See abdominal pain.
Red Flags / Complications
Untreated acute mesenteric ischemia can rapidly progress to necrosis, sepsis, and potentially death. The mortality for mesenteric ischemia requiring surgery exceeds 50%.
Additionally, surgical management puts patient at risk of lifelong complications including dependancy on parenteral nutritional support.
Management
Initial Medical Management
In all patients with acute mesenteric ischemia, management includes:
- NPO and nasogastric decompression
- Fluid therapy to maintain adequate volume and perfusion as determined by urine output
- Supplemental oxygen
- Avoid vasopressors (exacerbates ischemia)
Pharmacological management consist of:
- Therapeutic anticoagulation (unfractionated heparin) to limit thrombus propagation
- Empiric broad-spectrum antibiotic therapy
- Proton pump inhibitor
Revascularization
Revascularization options depends on the nature of the occlusion (embolic or thrombotic) and whether the patient is a candidate.
For acute embolism:
- Open surgical embolectomy
- Percutaneous thrombus aspiration with or without pharmacologic thrombolysis
For acute thrombosis (acute-on-chronic):
- Open mesenteric bypass
- Retrograde open mesenteric stenting
- Percutaneous angioplasty and stenting