A health condition in which a blood clot is formed in the superior mesenteric vein (SMV) is called SMV thrombosis. This vein is located in the abdominal (belly) area and it supplies the intestines with blood. This blood clot may reduce the flow of oxygen-poor blood away from the bowels and cause damage, as well as serious complications. One of the most common symptoms of SMV thrombosis is abdominal pain. Generally, this is a medical emergency, and without immediate treatment, it may lead to death.
Sometimes, the intestines do not get enough oxygen-rich blood, which may also cause the tissue to die. In such cases, organ damage may occur throughout the body, and without immediate treatment, it can be fatal.
In some cases, this disorder is called mesenteric venous thrombosis, but it is a more general medical term. It refers to a blood clot in the superior mesenteric vein, inferior mesenteric vein, or any of their branches. In most diagnosed cases, the blood clot forms in the superior mesenteric vein.
Physicians consider this disorder rare because it affects between 1 in 5,000 and 1 in 15,000 inpatient hospital admissions. While it may occur at any age, it is commonly diagnosed in people between the ages of 40 and 50.
Types of SMV Thrombosis
Experts have divided this disorder into several types based on how the symptoms appear. These include:
- Acute – In such cases, symptoms often appear within 24 to 72 hours of blood clot formation. Approximately 60% to 80% of all diagnosed cases of SMV thrombosis are acute. This type of condition usually causes damage to the intestines because the blood cannot reach them.
- Subacute – People who develop this type of SMV thrombosis often experience symptoms over several days. Moreover, symptoms are usually less severe compared to the acute type. Therefore, in people with subacute SMV thrombosis, the blood can still reach the intestines, but it is not enough.
- Chronic – This type of SMV thrombosis usually does not cause symptoms because the blood reaches the intestines through collateral vessels. These are small blood vessels that form gradually to help the blood reach the intestines. Commonly, the chronic type of this disorder is diagnosed when doctors perform imaging tests for other reasons. Furthermore, about 20% to 40% of all diagnosed SMV thrombosis and chronic.
Symptoms
The symptoms are often different among people who develop this condition. While some of them do not have symptoms, others may have symptoms severe enough to be hospitalized. Sometimes, people with SMV thrombosis may develop portal hypertension (high blood pressure) and experience the following symptoms. Examples include:
- Bloody stools
- Bloating
- Nausea
- Vomiting
- Confusion
- Edema (swelling in the legs and feet)
- Severe abdominal pain
It is advised to see a doctor if you experience any of the previous symptoms, especially sudden and severe belly pain.
Causes
Healthcare providers have categorized into 3 main types causes of SMV thrombosis. For example:
- Direct injuries to the vein caused by inflammation or surgery.
- Certain health conditions that reduce blood flow in the mesenteric vein or its surrounding veins. These include cirrhosis, heart failure, compression caused by a tumor, and others.
- Blood clotting disorders that make you more prone to developing a blood clot in the body.
Sometimes, doctors cannot determine what exactly causes this disorder. In such cases, the condition is called idiopathic SMV thrombosis.
Risk Factors
Healthcare professionals have identified some factors that could increase your risk of developing SMV thrombosis. Check below some examples:
- Pancreatitis
- Liver disease (such as cirrhosis)
- Inflammatory bowel disease (IBD)
- Inherited or acquired blood-clotting disorders
- Heart failure
- Enlarged spleen
- Large abdominal tumors
- Pancreatic cancer
- Viral infections (such as COVID-19)
Furthermore, people who need abdominal surgery (such as a splenectomy) are also at increased risk of developing this condition.
What Are The Long-term Effects of SMV Thrombosis?
People who develop this condition may also experience some complications, especially if they do not get treatment. Examples include:
- Bowel ischemia (reduced blood flow to the intestines)
- Sepsis
- Venous hypertension that may lead to malnutrition or esophageal varices
- Organ failure
- Pulmonary embolism (this condition occurs when a blood clot forms in the lungs)
- Recurrent thrombosis
- Stroke
- Wound infections
- Gastrointestinal bleeding
- Short bowel syndrome
This article does not contain a full list of SMV thrombosis complications. However, you can consult with your healthcare professional about ways to reduce the risk or even prevent these complications.
How to Prevent SMV Thrombosis?
There is no sure way to prevent blood clots always. However, there are some tips that may help reduce the risk of developing them. Check below some examples:
- Regularly visit your physician (once per year)
- Administer medicines exactly as prescribed by your doctor
- If you notice new symptoms or worsening of the existing ones, immediately contact your doctor
- Lifestyle changes (such as quitting smoking, dietary changes, limiting or avoiding alcoholic drinks, and others)
Diagnosis
Usually, doctors suspect this condition based on the symptoms you experience. Sometimes, it is difficult to diagnose this condition because the symptoms SMV thrombosis causes are similar to other health conditions. However, to confirm this disorder, doctors may perform some imaging tests. These include:
- CT angiography – This is the most common imaging test used to confirm SMV thrombosis. It helps view blood flow through your blood vessels.
- MRI (magnetic resonance imaging) scans – This test is often done when the results of CT angiography are not clear.
Treatment
Generally, the treatment goal is to restore blood flow to the intestines, prevent further damage to the bowels, and prevent the formation of new blood clots. It is important to remember that SMV thrombosis is a medical emergency, and without immediate treatment, this disorder can be fatal. Check below some treatments:
- Blood-thinners (also known as anticoagulants) – Usually, these medicines are the first treatment for people who develop blood clots. They help get rid of the blood clots and prevent the formation of new ones. In most cases, doctors recommend a Heparin infusion or Warfarin. While some people may take anticoagulants for up to 6 months, people with blood-clotting disorders may need these medicines for the rest of their lives.
- Thrombolysis – This treatment involves a catheter (a long and flexible tube) through which doctors send medicines into the veins. They help destroy the blood clot.
- Thrombectomy – During this procedure, surgeons will remove the blood clot. Usually, doctors will use minimally invasive procedures to remove it.
- Bowel resection – This surgery is used to remove the damaged part of the intestine. It is often recommended when the blood clot completely blocks blood flow.
Frequently Asked Questions
When should I go to the ER?
Immediately call 911 or go to the nearest emergency room (ER) if you experience sudden and severe abdominal pain, especially if you are at increased risk of developing SMV thrombosis. Without immediate treatment, this condition can be fatal.
What is the mortality rate of SMV thrombosis?
Some research has shown that the 30-day mortality rate is about 27%. Moreover, roughly 36% of people have experienced recurrent SMV thrombosis. For more details, discuss it with your doctor.
What are the symptoms of SMV thrombosis?
While the primary symptom of this disorder is belly pain, some people may also experience nausea, vomiting, diarrhea, or constipation. Ask your healthcare provider if you have additional questions.
