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The mesenteric arteries supply blood to the large and small intestines. When one or more of the mesenteric arteries narrow or becomes blocked, blood flow is restricted and the intestines fail to get enough oxygen. This is called ischemia - an inadequate blood supply (circulation) to an organ due to blockage of blood vessels in the area.
Mesenteric ischemia usually involves the small intestine and occurs when. Severe abdominal pain can result. Iif the blockage worsens, tissues in the intestine may start to die due to lack of blood flow.
Acute vs. Chronic Mesenteric Ischemia
Mesenteric ischemia can be acute or chronic. In acute mesenteric ischemia, symptoms come on suddenly and a serious health crisis may result. With chronic mesenteric ischemia, symptoms develop gradually over time, but can radidly progress to an acute crisis without warning.
Mesenteric ischemia usually occurs in persons older than 60. Key risk factors include smoking, high cholesterol and coronary heart disease.
- Severe pain in the abdomen occurring within an hour of eating, lasting for 60 to 90 minutes.
- Weight loss (patients cut back on eating due to the pain)
Many symptoms of chronic mesenteric ischemia are frequently present in other conditions. Therefore detailed tests must be performed to obain a definitive diagnosis of mesenteric ischemia. In acute mesenteric ischemia, a patient may experience sudden, severe stomach pain that cannot be alleviated with narcotic pain medications, nausea or vomiting.
- Atherosclerosis: a narrowing or hardening of the arteries when plaque forms in the artery walls. Plaque, a sticky substance, consists of fats and other products circulating in the blood. As plaque builds up, arteries can narrow and stiffen. Eventually, plaque builds up and reduces blood flow through the arteries.
- Blood Clots: A clot or embolus travels to one of the mesenteric arteries and blocks blood flow. Such clots are more common in patients with heart disease an irregular heartbeat.
Other conditions that may cause mesenteric ischemia include:
- Aortic dissection, a tear in the aorta's inner layer
- Coagulation disorders
- Congestive heart failure
- Low blood pressure
- Occlusion or blockage of the veins in the bowel
- Fibromuscular dysplasia and arteritits, disorders of the blood
- Angiogram: An angiogram uses x-rays to view the body's blood vessels. When the test is used to visualize (image) the, the test is also called an arteriogram. To create x-ray images, dye is injected through a thin, flexible tube called a catheter, which is threaded into the desired artery from an access point, ususually the groin, but sometimes the arm. The dye, called contrast, enables blood vessels to be seen on an x-ray. Treatment through the catheter may also be started during the angiogram.
- Doppler Ultrasound: Doppler ultrasound uses high-frequency sound waves which bounce off blood vessels. This test is designed to measure blood flow, reveal problems with the structure of blood vessels and identify which arteries are blocked.
- Blood Tests: With mesenteric ischemia, especially the acute type, the white blood cells is often high. Tests may also show if the acid bevel in the blood is high, a condition called acidosis. This may indicate serious bowel injury.
- CT Scan: A CT scan (Computed tomography) creates detailed three-dimensional images from x-rays of slices of the body. It can reveal problems with arteries, such as aortic dissection, and abdominal organs.
- Magnetic Resonance Angiogram (MRA) Scan: An MRA scan creates rich three-dimensional images of blood vessels using magnetic images of slices of the body. Its cannot be used, however, when a person has metal implants, such as a pacemaker or artificial hip.
The goal of treatment is to reopen the blocked mesenteric arteries to restore adequate blood flow to the intestinesy.
Trans-aortic endarterectomy is a procedure often used to treat chronic mesenteric ischemia. The surgery is designed to remove the plaque blocking the mesenteric artery. A vascular surgeon makes an incision (surgical cut ) in the abdomen, or side, and removes the plaque from the inner lining of the blocked mesenteric artery.
In bypass surgery, the vascular surgeon bypasses the narrowed or blocked section of the artery by creating a new avenue for blood flow using either a vein from another part of the body (bypass graft) or a tube made from synthetic material. This creates a new path for blood to flow to the intestines.
Angioplasty and Stenting
In this procedure, sometimes performed at the time of the angiogram, the vascular surgeon inflates a small balloon inside a narrowed mesenteric artery. After widening the artery with angioplasty,the surgeon may insert a stent, a tiny metallic mesh tube that supports the artery's walls and keeps the blood vessels open.
Treatment for acute mesenteric ischemia is generally an emergency procedure because severe intestinal damage can develop over a short time. Thrombolytic agents and other clot-dissolving medications may be injected into blood vessels, frequently at the time of the angiogram. Sometimes, these medications can disssolve the clot. Otherwise, the vascular surgeon must remove the clot surgically, especially where intestinal damage is present. With acute mesenteric ischemia, some parts of the intestine may be damaged beyond repair and must also be removed.