Mesenteric ischemia is caused by a reduction in intestinal blood flow, which most commonly arises from occlusion, vasospasm, and/or hypoperfusion of the mesenteric vasculature. The clinical consequences can be catastrophic, including sepsis, bowel infarction, and death, making rapid diagnosis and treatment imperative.
Intestinal ischemia can be divided into acute and chronic, based upon the rapidity and the degree to which blood flow is compromised.
●Acute mesenteric ischemia refers to the sudden onset of intestinal hypoperfusion, which can be due to occlusive or nonocclusive obstruction of arterial or venous blood flow. Occlusive arterial obstruction is most commonly due to acute embolic or thrombotic occlusion of the superior mesenteric artery (SMA), while nonocclusive mesenteric ischemia from arterial hypoperfusion is most commonly due to primary splanchnic vasoconstriction, often associated with a low cardiac output state. Occlusive venous obstruction is most commonly due to acute thrombosis of the superior mesenteric vein (SMV) or segmental intestinal strangulation (eg, strangulated hernia, volvulus).
●Chronic mesenteric ischemia (also called intestinal angina) refers to episodic or constant intestinal hypoperfusion, which usually develops in patients with chronic mesenteric atherosclerotic disease; the symptoms of this condition are strongly associated with meals.
Acute mesenteric ischemia involving the small intestine will be reviewed here. Chronic mesenteric ischemia, which generally refers to small bowel ischemia, and colonic ischemia are discussed separately. (See "Chronic mesenteric ischemia" and "Colonic ischemia".)