Mesenteric ischemia causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Feham Tariq, MD [2]

Overview

Narrowing of the arteries that supply blood to the intestine causes mesenteric ischemia. The arteries that supply blood to the intestines run directly from the aorta. Mesenteric ischemia is often seen in people who have hardening of the arteries in other parts of the body (for example, those with coronary artery disease or peripheral vascular disease). The condition is more common in smokers and in patients with high blood pressure or blood cholesterol. Mesenteric ischemia may also be caused by an embolus that suddenly blocks one of the mesenteric arteries. The emboli usually come from the heart or aorta. These clots are more commonly seen in patients with arrhythmias, such as atrial fibrillation.

Causes

Mesenteric ischemia can be broadly classified into four categories:

• Arterial thrombosis
• Arterial embolism
• Venous thrombosis
• Non-occlusive ischemia

Classification based on etiology
Etiology	Cause	Incidence	Examples	Mechanism
Occlusive causes	Aterial embolism	50-70%	Superior mesenteric artery obstruction (most common cause) Arrhythmia Myocardial infarction Infective endocarditis Valvular heart diseases Ventricular aneurysms History of embolic events Recent angiography	Acute mesenteric arterial embolism: Attributes to 50% cases of mesenteric ischemia. Mesenteric embolus can oringinate from the left atrium, associated with cardiac arrythmias such as atrial fibrillation. Recent myocardial infarction resulting in segmental wall motion abnormality leading to poor ejaction fraction and embolus formation. Infective endocarditis: vegetations on the cardiac valves resulting in turbulence in blood flow predisposing to formation of emboli into the blood stream.
	Arterial thrombosis	15-25%	Atherosclerosis Advanced age Prolonged hypotension Hypercoagulabilty states Peripheral arterial disease Traumatic injury	Acute mesenteric arterial thrombosis: 25% cases of mesenteric ischemia result from mesenteric arterial thrombosis. Most likely due to underlying atherosclerosis(plaque formation) leading to stenosis. An underlying plaque(fatty streak) in the superior mesenteric artery leads to critical stenosis over the years forming collaterals.
	Venous thrombosis	5%	Right-sided heart failure Previous deep venous thrombosis (20-40% risk) Primary clotting disorder Pancreatitis Polycythemia Sickle cell anemia Recent abdominal surgery or infection
Non-Occlusive causes	Non-occlusive ischemia	20-30%	Low cardiac output states(most commom cause) Hypovolemia Vasoconstrictive drugs (Digoxin, alpha-adrernergic agonists) Septic schock Aortic insufficiency Cocaine abuse or ergot poisoning Inflammatory bowel disease
Rare causes	Splanchnic artery stenosis