Acute mesenteric ischemia has multiple causes. The most common are
Arterial embolism is a blood clot or piece of atherosclerotic plaque material (the buildup of cholesterol and other fatty materials in an artery) that travels from its origin in the heart or aorta to lodge in the smaller arteries (in this case those of the intestines).
Arterial thrombus is a blood clot that forms spontaneously in the arteries or veins, including those of the intestines, blocking flow.
Sometimes flow is not blocked completely but is simply too low because of low heart output (as in heart failure or shock) or because certain drugs (such as cocaine) narrow the blood vessels. In general, people older than 50 years are at greatest risk.
Blockage of blood flow for more than 6 hours can cause the affected area of intestine to die, allowing intestinal bacteria to invade the person's system. Shock, organ failure, and death are likely if intestinal death occurs.
At first, the person has severe abdominal pain, usually developing suddenly, but only mild pain occurs when the doctor presses on the abdomen during the examination (unlike in disorders such as appendicitis or diverticulitis, in which pressing makes the pain much worse). Later, as the intestine starts to die, the doctor's examination of the abdomen causes more severe pain.
If the person has typical symptoms of acute mesenteric ischemia or if the abdomen is very tender, doctors usually take the person right to surgery.
If the diagnosis of acute mesenteric ischemia is not clear, doctors do CT angiography (a special CT scan using radiopaque dye injected in an arm vein to produce images of blood vessels) to look for swelling of the intestines or blockages in the arteries that supply blood to the intestines.
If the doctor can make the diagnosis and begin treatment early, people usually recover well. If the diagnosis is not made or if treatment is not started until some of the affected intestine has died, 70 to 90% of people die. A person cannot survive if almost all the small intestine dies or is removed.
If mesenteric ischemia is diagnosed during surgery, the blood vessel blockage can sometimes be removed or bypassed, but other times the affected intestine must be removed.
If mesenteric ischemia is diagnosed during CT angiography, doctors may try to relieve the blockage in the blood vessels using angiography. In angiography, a small flexible tube (catheter) is threaded through the artery in the groin and into the arteries of the intestines. If a blockage is seen during angiography, sometimes it can be opened by injecting certain drugs, suctioning out a blood clot using a special angiography catheter, or inflating a small balloon within the artery to widen it and then placing a small tube or manufactured mesh (stent) to keep it open. If doctors cannot successfully open the blockage using these procedures, the person needs surgery to open the blockage or to remove the affected portion of the intestine.
After recovery, many people need to take a drug to help prevent blood clotting.