Causes

Intestinal ischemia occurs when the blood flow through the major arteries that supply blood to your intestines slows or stops. The condition has many potential causes, including a blockage in an artery caused by a blood clot, or a narrowing of an artery due to buildup of deposits, such as cholesterol. Blockages also can occur in veins, but they're less common.

Intestinal ischemia is often divided into categories:

Colon ischemia (ischemic colitis)

This type of intestinal ischemia, which is the most common, occurs when blood flow to the colon is slowed. The cause of diminished blood flow to the colon isn't always clear, but a number of conditions can make you more vulnerable to colon ischemia:

• Dangerously low blood pressure (hypotension) associated with heart failure, major surgery, trauma or shock
• A blood clot in an artery supplying the colon
• Twisting of the bowel (volvulus) or trapping of intestinal contents within a hernia
• Excessive bowel enlargement from bowel obstruction caused by scar tissue or a tumor
• Other medical disorders that affect your blood, such as inflammation of your blood vessels (vasculitis), lupus or sickle cell anemia
• Medications that constrict blood vessels, such as some used to treat heart disease and migraine
• Hormonal medications, such as birth control pills
• Cocaine or methamphetamine use
• Vigorous exercise, such as long-distance running

Acute mesenteric ischemia

This type of intestinal ischemia usually affects the small intestine. It has an abrupt onset and may be due to:

• A blood clot (embolus) that dislodges from your heart and travels through your bloodstream to block an artery, usually the superior mesenteric artery, which supplies oxygen-rich blood to your intestines. This is the most common cause of acute mesenteric artery ischemia and can be brought on by congestive heart failure, an irregular heartbeat (arrhythmia) or a heart attack.
• A blockage that develops within one of the main intestinal arteries and slows or stops blood flow, often as a result of fatty deposits (atherosclerosis) building up on the wall of an artery. This type of sudden ischemia tends to occur in people with chronic intestinal ischemia.
• Impaired blood flow resulting from low blood pressure due to shock, heart failure, certain medications or chronic kidney failure. This is more common in people who have other serious illnesses and who have some degree of atherosclerosis. This type of acute mesenteric ischemia is often referred to as nonocclusive ischemia, which means that it's not due to a blockage in the artery.

Chronic mesenteric ischemia

Chronic mesenteric ischemia, also known as intestinal angina, results from the buildup of fatty deposits on an artery wall (atherosclerosis). The disease process is generally gradual, and you may not require treatment until at least two of the three major arteries supplying your intestines become severely narrowed or completely obstructed.

A potentially dangerous complication of chronic mesenteric ischemia is the development of a blood clot within a diseased artery, causing blood flow to be suddenly blocked (acute mesenteric ischemia).

Ischemia that occurs when blood can't leave your intestines

A blood clot can develop in a vein draining deoxygenated blood from your intestines. When the vein is blocked, blood backs up in the intestines, causing swelling and bleeding. This is called mesenteric venous thrombosis, and it may result from:

• Acute or chronic inflammation of your pancreas (pancreatitis)
• Abdominal infection
• Cancers of the digestive system
• Bowel diseases, such as ulcerative colitis, Crohn's disease or diverticulitis
• Disorders that make your blood more prone to clotting (hypercoagulation disorders), such as an inherited clotting disorder
• Medications such as estrogen that can increase clotting risk
• Abdominal injuries