What is Mesenteric Artery Ischemia?
Intestinal ischemia is a condition that affects the blood flow to the intestines. This problem can impact the small intestine or the colon. In medical terms, “colonic ischemia” is when the blood supply to the colon is interrupted, and “mesenteric ischemia” occurs when the blood vessels delivering blood to the small intestines are affected. This can be due to a blockage, which may or may not affect the arteries, or because the veins carrying blood away from the intestines are obstructed.
Acute mesenteric ischemia refers to a sudden reduction in blood flow to the small intestines. If this happens, patients usually feel sudden abdominal pain. This is a serious condition and patients may quickly get worse; thus, urgent surgical intervention is often required.
Chronic mesenteric ischemia is a long-term condition that is usually associated with narrowing of the small intestinal vessels due to plaque build-up, a condition known as ‘mesenteric atherosclerosis’. This leads to intermittent decrease in blood flow to the intestines, usually becoming more pronounced after eating.
What Causes Mesenteric Artery Ischemia?
The main causes of mesenteric ischemia, a condition where blood flow to your intestines is reduced, include:
1. Mesenteric Arterial Embolism: This typically happens when a blood clot gets stuck in the superior mesenteric artery, the main vessel that supplies blood to your small intestines, causing sudden severe pain. Risk factors include heart muscle disease, irregular heart rhythm, recent procedures involving the blood vessels, inflammation of the blood vessels, and valve-related heart conditions.
2. Mesenteric Arterial Thrombosis: This is often caused by a condition called atherosclerosis, which is the hardening of your arteries due to plaque buildup. This can lead to the formation of clots, either by causing the plaque to rupture suddenly, or by gradually narrowing the artery until the blood flow becomes critically restricted. Risk factors include conditions like atherosclerosis, disease of the arteries in your arms and legs, tendency to form excessive clots, use of estrogen therapy, and prolonged low blood pressure.
3. Mesenteric Venous Thrombosis: This involves the formation of blood clots in the veins that drain blood from the intestines. This increases the pressure in these veins and slows down the blood flow. Patients with inflammatory conditions in their abdomen (such as inflammatory bowel disease) or people who are prone to forming excess blood clots due to underlying genetic conditions, acquired conditions, or cancers are at a higher risk.
4. Nonocclusive Mesenteric Ischemia (NOMI): This usually happens due to a sudden narrowing or “spasm” of the superior mesenteric artery. This can severely reduce blood flow to the small intestine and large intestine. Risk factors include diseases of the arteries in your limbs, severe infection leading to shock, medicines that narrow your blood vessels (like digoxin), illicit drug use such as cocaine, or kidney disease requiring dialysis, among many other conditions.
Risk Factors and Frequency for Mesenteric Artery Ischemia
Mesenteric ischemia, a condition affecting the blood supply to the intestines, is rare. While the exact percentage is unknown, it’s believed that about 0.09% to 0.2% of all hospital admissions in the U.S. are due to this condition.
The causes of mesenteric ischemia vary and they are estimated as follows:
- 50% are due to mesenteric arterial embolism, which is a blood clot in an artery supplying the intestines.
- 15% to 25% are due to mesenteric arterial thrombosis, a blockage in an artery that supplies the intestines.
- 5% are due to mesenteric venous thrombosis, a blood clot in a vein that drains blood from the intestines.
- 20% are due to nonocclusive mesenteric ischemia, a condition caused by decreased blood flow to the intestines.
This condition usually affects older people, especially those with cardiovascular disease. In younger people without any known heart disease, the main cause of mesenteric ischemia is most often venous thrombosis.
Signs and Symptoms of Mesenteric Artery Ischemia
When assessing patients for mesenteric ischemia, a condition dealing with poor blood flow to the intestines, it’s crucial to thoroughly examine both their personal and family medical history. Interestingly, about 30% of patients showing symptoms of acute mesenteric ischemia due to a blood clot have experienced a similar event before. Similarly, those who display signs of acute mesenteric venous thrombosis, which is a blood clot in the intestinal vein, often have a personal or family history of deep vein thrombosis or pulmonary emboli about 50% of the time.
The most frequently reported symptom of this condition is abdominal pain. However, the nature of the pain and additional symptoms can differ depending on the cause of the ischemia. For example, a blockage in the arterial blood supply to the intestines, or arterial embolism, typically triggers sudden and intense belly button pain, often accompanied by nausea and vomiting. If a patient’s abdominal pain worsens after eating, they might be dealing with a clot or blockage in the mesenteric artery. On the other hand, individuals with mesenteric venous thrombosis, a clot in the intestinal vein, typically experience a unique type of abdominal pain which gradually develops and varies in intensity.
A physical examination may not always reveal abnormal findings, as the severity of the pain experienced by patients tends to exceed what’s observable in the initial physical check-up. Mild distension, or swelling, might be present, but signs of peritoneum, the membrane lining the abdominal cavity, usually only become evident when there’s severe damage to the bowel tissue, typically due to intestinal blood supply blockage and the subsequent death of tissue.
Testing for Mesenteric Artery Ischemia
The best way to diagnose mesenteric ischemia, a condition that reduces blood flow to the intestines, is through a procedure called mesenteric angiography. However, computed tomography angiography, a form of CT scan that looks at blood vessels, is usually good enough for initial diagnosis. Doctors might also conduct lab tests like checking your white blood cells, d-dimer (a small protein fragment present in the blood after a blood clot is degraded), and lactate (a substance produced by cells during rapid energy production) levels to help in the diagnosis. But, these tests alone are not definitive and can sometimes give false positives.
That’s why the most critical part of the diagnosis is a thorough medical history check and physical examination performed by your doctor, along with continuous monitoring of your abdomen. This allows the doctor to gather more information and make a more accurate diagnosis.
Treatment Options for Mesenteric Artery Ischemia
For people experiencing ‘acute mesenteric ischemia’, which is a rapid decrease in blood flow to the intestines, immediate surgery is usually required. Once arriving at the emergency department, treatment will start immediately to help your body deal with this serious medical condition. This includes replacing lost fluids in your body (fluid resuscitation) and fighting off potential infections with a wide range of antibiotics (broad-spectrum antibiotics).
Some patients might have a condition known as “hypotension”, where their blood pressure is unusually low. In cases where this doesn’t improve even after the fluid treatment, a medication called ‘norepinephrine’, which can help raise blood pressure, may be administered. However, doctors have to be cautious when using this medication as it might, in certain cases, worsen the existing blood flow problem (ischemia).
If the issue of reduced blood supply to your intestines is caused by a blockage called an ’embolism’, the treatment generally involves an emergency surgical procedure known as ‘laparotomy’ to remove the blockage (embolectomy). Sometimes, if the condition is diagnosed incredibly early and there are no signs of inflammation in the lining of the abdomen (peritonitis), a medication to dissolve the clot could be used directly at the site of the embolism.
When the blood flow issue is due to a blood clot forming in an artery supplying the intestines (mesenteric arterial thrombosis), the usual treatment is surgery to restore blood flow (revascularization) or a procedure to widen the artery using a small mesh tube (stenting).
If the blood flow issue is because a blood clot has formed in a vein (mesenteric venous thrombosis), the condition might sometimes be managed with medication that reduces the likelihood of your blood forming clots (systemic anticoagulation), but this highly depends on the severity of the disease.
For some people, the blood flow problem might be due to spasm of the arteries supplying the intestines (NOMI), and in such cases, treatment aims to address the underlying reason for these artery spasms, like stopping any medications that might be causing the spasms.
Generally, unless there are reasons not to use them (contraindications), medications to reduce the risk of further blood clots (systemic anticoagulation) will be given after the surgery.
What else can Mesenteric Artery Ischemia be?
Mesenteric ischemia, a condition that restricts blood flow to the intestines, can show up in many forms and can be hard to distinguish from other conditions based on a physical exam alone. It’s therefore crucial to keep this potential diagnosis at the forefront, especially in older patients who have risk factors. Other conditions that might be confused with mesenteric ischemia include:
- An abrupt rupture of an abdominal aortic aneurysm
- A tear or hole in the bowel
- An obstruction in the bowel
It’s also worth considering any sudden and serious abdominal conditions as the potential cause. The key is to consistently, in the right situations, think about the possibility of mesenteric ischemia.
What to expect with Mesenteric Artery Ischemia
The estimated death rate for this condition is between 60% and 80%, especially if the diagnosis is delayed by more than 24 hours. If surgical treatment is started within 6 hours of the appearance of symptoms, chances of survival increase significantly. Generally, the outlook for patients depends on the cause of the condition. Those with an artery-related cause have worse survival rates compared to those with a vein-related cause.
Possible Complications When Diagnosed with Mesenteric Artery Ischemia
If mesenteric ischemia, a condition that restricts blood flow to the intestines, isn’t treated promptly, it can lead to several complications. These include:
- Death of intestinal tissue, known as necrosis
- Breach or holes in the intestinal wall, which is referred to as perforation
- In severe cases, it can even be fatal
Recovery from Mesenteric Artery Ischemia
People suffering from acute mesenteric ischemia, a condition that blocks blood flow to the intestines, require specialized treatment in the hospital’s intensive care unit after undergoing surgery. Most patients then go through another operation called a “second-look laparotomy” within 24 to 48 hours following the initial procedure to improve blood flow, as this is critical for checking the state of the intestines. Unless there are specific reasons against it, patients are normally put on a long-term medication that thin the blood after their hospital stay to help prevent blood clots.
If a small metal tube known as a mesenteric artery stent is inserted to keep the blood vessel open, it’s important to regularly monitor its condition. This can be done with imaging techniques like duplex ultrasound or CT angiography which create pictures of the blood vessels. Nonetheless, there’s not a lot of research on how often this monitoring should be done.
