Mesenteric Ischemia

Symptoms and Effects of Acute and Chronic Intestinal Ischemia

Jul 20, 2009 David Henry

Mesenteric ischemia is a potentially fatal condition in which the intestines and the surrounding fat do not receive enough blood and oxygen.

The pathophysiology, causes, and effects of acute and chronic mesenteric ischemia are discussed below. Other articles discuss the Symptoms, Diagnosis, and Outcomes of mesenteric ischemia and the Treatment Options.

Pathophysiology of Mesenteric Ischemia

Mesenteric ischemia can result from an arterial embolus (clot from another location), arterial thrombus, vasospasm (constriction of the blood vessels), or venous thrombosis. Vasospasm causing mesenteric ischemia is also called nonocclusive mesenteric ischemia (NOMI), since there is no clot within the arteries or veins. More than 50% of mesenteric ischemia is caused by an embolus (clot), usually from within the heart. The embolus lodges within the superior mesenteric artery (a main artery supplying the intestines) 50% of the time.

Thrombosis can also cause mesenteric ischemia in patients with atherosclerosis (plaque within the blood vessels). Vasospasm (NOMI) often occurs in very sick, hospitalized patients who are receiving “vasopressor” medications, which help to maintain a normal blood pressure. These medications constrict the blood vessels in the body to increase the blood pressure in patients with a low blood pressure. However, constricting the blood vessels can also prevent enough blood from reaching the mesentery and intestines, causing mesenteric ischemia.

The superior mesenteric vein is occluded in 95% of cases of mesenteric venous thrombosis. Some patients who develop mesenteric venous thrombosis have a blood clotting disorder, allowing blood to clot more easily.

Effects of Mesenteric Ischemia

Acute Mesenteric Ischemia

Ischemia occurs when not enough blood and oxygen can reach the mesentery (fatty tissue) and intestines. The intestinal mucosa can slough off within 3 hours, and infarction (cell death) of the intestines can occur within 6 hours.

Chronic Mesenteric Ischemia

If blood flow is reduced gradually, as in chronic mesenteric ischemia, then additional blood vessels can be recruited over time to supply the intestines with blood. If enough “collateral” blood supply is recruited, then infarction (cell death) usually does not occur. Chronic mesenteric ischemia results from atherosclerosis (plaques) gradually blocking off the celiac artery, superior mesenteric artery, and/or inferior mesenteric artery, all of which supply the intestines with blood. Symptoms occur when two or three of these arteries become severed stenosed (narrowed or blocked).

References

Acute mesenteric ischemia. Feldman: Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 8th ed. Saunders, 2006.

Chapter 27: Small intestine. Brunicardi C et al., Eds. Schwartz’s Principles of Surgery. 4th ed. McGraw-Hill, 2005.

eMedicine: Mesenteric Ischemia

Levy, Angela D. Mesenteric ischemia. Radiologic Clinics of North America 2007. 45:593-9.

Vascular Web: Mesenteric Ischemia

The copyright of the article Mesenteric Ischemia in General Medicine is owned by David Henry. Permission to republish Mesenteric Ischemia in print or online must be granted by the author in writing.

Blood flow to the intestines

Aortogram: Narrowed superior mesenteric artery

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