An Overview of Intestinal Ischemia

Intestinal ischemia is a serious condition caused by insufficient blood flow to part of the intestine. Whether it affects the small or large intestine, the chief symptom is pain. The pain may be severe and sudden, or it may be a milder and intermittent pain that usually occurs after meals. If the intestinal blood supply becomes sufficiently compromised, Intestinal ischemia can lead to intestinal rupture, sepsis (severe infection), and death. For this reason, it is important for intestinal ischemia to be diagnosed and treated as quickly as possible.

Symptoms

Intestinal ischemia can be acute or chronic, with the symptoms of each being slightly different.

Acute Intestinal Ischemia

Pain caused by acute vascular occlusion to the intestines usually is located in the region of the umbilicus (belly button). Symptoms are severe enough that people who have this condition will virtually always seek immediate medical help.

Intestinal ischemia sometimes causes part of the small or large intestine to die—a condition called intestinal infarction. Intestinal infarction allows the contents of the intestine to leak into the abdominal cavity, spreading inflammation and infection (a condition called peritonitis). Peritonitis, a life-threatening condition, is extremely painful, and is accompanied by nausea, vomiting, fever, and a rigid, very tender abdomen.

Chronic Intestinal Ischemia

Intestinal ischemia can also be a milder, more chronic condition. This milder form is caused by partial blockages, resulting from atherosclerotic plaques, in the arteries supplying the intestines.

People with chronic intestinal ischemia often experience intermittent, dull, nondescript abdominal pain after they eat a meal. The pain occurs after eating because the intestines require more blood flow during digestion, and the partially blocked arteries cannot supply that extra blood. 

People with this milder form of intestinal ischemia often do not seek medical help right away, and instead may subconsciously cut back on meals to avoid discomfort. They often have substantial weight loss before they finally ask their doctor for help. Unfortunately, many never get a medical evaluation until they finally develop acute intestinal ischemia.

Causes

Intestinal ischemia usually occurs when one of two major arteries becomes obstructed: the superior mesenteric artery (SMA), which supplies most of the small intestine; or the inferior mesenteric artery (IMA) the major supplier of the large intestine. Sometimes a blockage in the venous drainage from the intestines can also lead to intestinal ischemia.

There are several general vascular conditions that can cause acute intestinal ischemia. These include:

• Arterial embolism: An embolus—a blood clot that breaks loose and travels through the circulation—can become lodged in a mesenteric artery, causing a blockage. Because an embolus tends to be a sudden event, symptoms are usually acute and quite severe. Embolism is estimated to be the cause of about half the cases of intestinal ischemia.
• Arterial thrombosis: A thrombus (a blood clot that forms within a blood vessel) probably accounts for 25% of cases of acute intestinal ischemia. Similar to coronary artery thrombosis, thrombosis of the mesenteric arteries seems to occur when an atherosclerotic plaque in the lining of the artery ruptures. Just as people with coronary artery disease will often experience intermittent angina with exertion before they have an actual heart attack, people with thrombosis of a mesenteric artery will often describe prior symptoms of intermittent abdominal pain following meals—so-called "intestinal angina."
• Venous thrombosis: If one of the veins draining blood from the intestines (the mesenteric veins) becomes blocked, blood flow through the affected intestinal tissue slows markedly, leading to intestinal ischemia. This condition is most often seen in people who have had recent abdominal surgery, people with cancer, or people with an increased risk of forming clots.
• Nonocclusive intestinal ischemia: Sometimes, blood flow through the mesenteric arteries drops markedly without any local blockages at all. This condition is usually seen in people who are severely ill and in shock, most often from severe cardiac disease or sepsis. In these catastrophic conditions, circulating blood is shunted away from "non-vital" organs in favor of the heart and brain and, as a result, intestinal ischemia may occur.

Risk Factors

Almost any form of cardiac disease, vascular disease, or disorders of blood clotting can increase a person's risk of developing intestinal ischemia.

In particular, the risk of intestinal ischemia increases with:

• Heart disease: This includes heart valve disease, atrial fibrillation, or cardiomyopathy. These conditions allow blood clots to develop within the heart, which can then embolize. While stroke is the main concern of doctors and patients when blood clots form in the heart, an embolus from the heart can also cause acute intestinal ischemia.
• Peripheral artery disease (PAD): When PAD involves the mesenteric arteries, intestinal ischemia can result.
• Blood clotting disorders: Inherited blood clotting disorders, such as factor V Leiden, account for the majority of people who have intestinal ischemia without underlying vascular disease.
• Hypovolemia, or low blood volume: Reduced blood volume can be caused by excessive bleeding, severe dehydration, or cardiovascular shock, and can produce nonocclusive intestinal ischemia.
• Inflammation of the blood vessels: Vasculitis (inflammation of blood vessels) can be produced by infections or autoimmune disorders such as lupus. The vascular inflammation can lead to thrombosis of the mesenteric arteries.

Diagnosis

The key to diagnosing acute intestinal ischemia is for the doctor to think of the diagnosis, and then do the appropriate testing to confirm it or rule it out.

The key symptom of intestinal ischemia is abdominal pain. However, there are scores of medical conditions that produce abdominal pain, so in order for the doctor to focus on the possibility of intestinal ischemia, he or she must always be ready to consider this diagnosis. 

People with intestinal ischemia often have very few findings on physical exam and, in fact, young doctors are taught to think of this condition any time a patient complains of severe pain that is out of proportion to the physical findings. The doctor's level of concern should increase in a patient with unexplained sudden abdominal pain who also has risk factors for intestinal ischemia, and in patients who describe a history of abdominal pain after meals.

Once intestinal ischemia is deemed to be a reasonable possibility, specialized imaging studies of the abdomen should be performed immediately. In many cases, abdominal CT scanning or MRI scanning can help make the diagnosis. CT angiography (a CT scan combined with the injection of a dye into a vein) or conventional arteriography (a catheterization technique in which dye is injected into an artery and x-rays are done) is often required to confirm the diagnosis.

If suspicion of acute intestinal ischemia is high enough, or if there are signs of peritonitis or cardiovascular instability, immediate exploratory surgery may be necessary before a definitive diagnosis can be made.

Treatment

In treating acute intestinal ischemia, it is important to stabilize the patient as rapidly as possible, while working to restore blood flow to their intestines. 

Typically, fluids are administered to restore and maintain blood circulation, pain control is achieved with opioids, antibiotics are given to try to prevent any leakage of intestinal bacteria into the abdominal cavity from producing peritonitis, and anticoagulant medication is given to prevent further blood clotting.

If signs of deterioration or of peritonitis should appear, surgery should be performed right away to remove the dying portion of intestine and to surgically restore blood flow through the occluded SMA or IMA. 

If emergency surgery is not required, options for restoring blood flow include anticoagulant drugs, bypass surgery, angioplasty and stenting, or administering "clot-busting" drugs. The optimal choice can be difficult, and often requires a team approach involving a gastroenterologist, cardiologist, and surgeon. 

In a person who has been diagnosed with chronic intestinal angina, that is, partial occlusion of the SMA or IMA caused by an atherosclerotic plaque, treatment can be accomplished either with bypass graft surgery, or with angioplasty and stenting. This treatment will make it easier to eat meals without symptoms and should help to prevent acute intestinal ischemia from occurring.

Outcomes

Acute intestinal ischemia is a severe medical condition that can be challenging to diagnose rapidly and difficult to treat. The outcomes usually depend on the underlying cause. Unfortunately, the risk of dying with this condition is quite high with acute arterial ischemia—approaching 50%—but the risk appears to be substantially lower in people who are diagnosed rapidly. This risk is also lower in patients with venous thrombosis.

Once a person with acute intestinal ischemia has been treated and stabilized, the long-term outcome depends largely on the nature of the underlying cardiovascular problem (or other medical conditions) that led to the intestinal ischemia in the first place.

In any case, recovering from acute intestinal ischemia can be a challenge. These individuals tend to be older, and usually have substantial underlying cardiovascular disease. They may also have a temporary (or in some cases a permanent) colostomy or ileostomy, if a partial intestinal resection has been required. 

In all cases, they will need thorough management of any underlying cardiovascular conditions that have contributed to their intestinal ischemia. They will also need a full evaluation of contributing risk factors—including hypertension, cholesterol, obesity, smoking, and diabetes—and will need to aggressively manage these. 

A Word From Verywell

Intestinal ischemia is a serious condition caused by reduced blood flow to part of the intestine. While the condition may begin with mild symptoms, it may lead to catastrophic results. Early diagnosis and treatment are the keys to a successful outcome.