What is Vein Obstruction?
The circulatory system has different types of blood vessels, and one group is called the venous system. These are the vessels that carry blood back to the heart from the body’s tissues and organs. Most veins carry blood without a lot of oxygen, except for the umbilical vein that is open during the growth of a baby and closes after birth, and the pulmonary vein.
Veins are made up of three layers. The outer layer is made of connective tissue (tunica adventitia or tunica externa); the middle layer is smooth muscle (tunica media); and the inner layer is made of cells that line the interior of the blood vessel (tunica intima). The middle layer of muscle is thinner in veins compared to arteries which helps increase its capacity to hold blood; however, veins need valves to ensure blood only flows in one direction.
Sometimes, these veins can get blocked. This means that the vein is partially or completely closed off, which can cause less blood to flow and more blood to pool in the vein. The most common type of blockage happens deep in the veins of the lower legs, causing the blood to thicken and form small blood clots. This happens when something slows down or blocks the flow of blood in the veins. Damage to the inside lining of the vein from injury or disease is one of the most common causes.
Sometimes, the balance between the substances in our blood that cause clotting and those that prevent it can be off, leading to a state where clots form easily. Chronic venous insufficiency, a condition where the veins don’t function well, is a result of a weak vein wall and dysfunctional vein valves.
Obstruction can also happen in the portal vein, a major vein leading to the liver, usually manifesting as a blood clot.
What Causes Vein Obstruction?
Venous thromboembolism (VTE) is a condition where blood clots form, often due to particular risk factors.
These risk factors can be inherited or acquired through one’s lifestyle or experiences. Inherited risk factors include a condition called Factor V Leiden, which is the most common. However, this condition doesn’t typically cause blood clots by itself – other risk factors usually play a part too.
Acquired risk factors include prolonged immobilization. During periods where you’re not moving much like when you’re on bed rest, on long plane flights, or in the intensive care unit of a hospital, your risk of blood clots can go up. This happens because your muscles aren’t actively helping to move your blood around, which can lead to blood pooling and clot formation.
Additionally, any direct or indirect injury to your veins, or certain surgical procedures, can also increase your risk of developing clots.
Being pregnant can also raise your risk of VTE. This is because pregnancy causes your blood to clot more easily. For example, the amount of fibrinogen, a protein that aids in clotting, can triple during pregnancy, while levels of Protein S, which helps prevent clotting, decrease.
Taking birth control pills or hormone replacement therapy can also increase your risk because they raise fibrinogen levels in your blood. Being overweight is also linked to a higher risk of VTE.
Smoking can increase your risk too, as nicotine and other chemicals in cigarettes increase the levels of certain substances in your blood that help form clots.
Certain types of cancer, as well as some cancer treatments, can also heighten your risk because they increase substances in your body that promote clotting.
Another risk factor is heart failure, which can reduce the heart’s functioning and lead to an increase in blood pooling.
Finally, having inflammatory bowel diseases like Crohn’s disease or ulcerative colitis can raise your chances of having deep vein thrombosis, a type of VTE where the blood clot forms deep within your veins.
Risk Factors and Frequency for Vein Obstruction
Every year in the United States, about 4 million surgical patients and 8 million medical patients are at medium or high risk for Venous Thromboembolism (VTE), which is a condition where blood clots form in the veins. According to a worldwide study, a large number of hospital patients worldwide are also at moderate or high risk. Specifically, 42% of medical patients and 64% of surgical patients are at risk.
- The top four risk factors for VTE among hospitalized medical patients include:
- Previous history of VTE
- Bed rest
- Placement of a medical device called a ‘peripherally inserted central venous catheter’
- Cancer
- VTE can also happen in people who aren’t in the hospital. For example, in a community study, about 3 out of 4 patients developed VTE at home.
- Over half of these individuals had either undergone surgery or been in the hospital in the past three months.
- If a person has cancer, a severe infection, or heart failure, their chance of not doing well if they get VTE is higher.
A research study in Norway found out that for every 1000 person-years, there were 1.43 first time occurrences of VTE, with 0.93 of these being Deep Vein Thrombosis (DVT). The chance of dying within 30 days of developing DVT was about 4.6%. As people got older, the chances of developing VTE went up. Furthermore, women had a slightly higher risk of developing VTE than men.
Signs and Symptoms of Vein Obstruction
Venous obstruction often takes the form of deep venous thrombosis (DVT), leading to common symptoms like one or both legs swelling. This usually happens after long periods of inactivity, such as a long flight. Other symptoms can include leg pain, which half of patients experience and which worsens when the foot is flexed upwards. Swelling (edema) is a key sign of DVT if present. However, the size of the blood clot doesn’t necessarily relate to the level of pain experienced or tenderness felt.
The symptoms are usually only found in the leg affected by the DVT. For example, the calf may be tender and pain may be felt when the foot is flexed upwards (a positive Homans sign). Swelling of 2 centimeters or more in the affected leg is a strong indicator of DVT, and a positive D-dimer test is highly correlated with DVT.
Portal vein thrombosis is associated with different symptoms, such as pain in the upper right side of the abdomen, nausea, and/or a fever. Patients might experience an increase in abdominal fluid (ascites) and reduced blood supply to the intestine due to small blood clots forming in the vessels. Intestinal damage due to sudden high blood pressure in the veins leading to the liver (portal hypertension) can also occur.
Testing for Vein Obstruction
To evaluate your risk for deep venous thrombosis (DVT), which is a blood clot in a deep vein, usually in the leg, your doctor may order a variety of blood tests. These tests may include the D-dimer assay, antithrombin III (a protein that helps control blood clotting), N-terminal pro-brain natriuretic peptide (a substance that is released when your heart is under stress), and C-reactive protein (a sign of inflammation in your body), as well as the erythrocyte sedimentation rate (a measure of inflammation). The main indication for DVT is a positive D-dimer result alongside leg swelling.
Your doctor may also want to get a closer look at your veins using medical imaging. They may order an ultrasound, which uses sound waves to create an image of your veins, of the affected leg and pelvic area. In some instances, they may also want to conduct other imaging studies, such as a computed tomography (CT) scan or a magnetic resonance imaging (MRI). These are types of imaging that provide detailed pictures of the inside of your body.
If your doctor suspects that you have a blood clot in your portal vein (a large vein that carries blood to your liver), they may conduct additional tests. These can include blood clotting tests to rule out inherited disorders that can cause excessive clotting, liver function tests to see how well your liver is working, and additional imaging tests. The first choice for imaging is usually ultrasound. In some cases, the doctor may want to look at your veins in more detail using MRI or MRA (which can show blood flow), or possibly a CT scan.
Treatment Options for Vein Obstruction
The management of venous thromboembolism (VTE), a condition involving blood clots in your veins, aims to prevent the existing clot (known as deep vein thrombosis or DVT) from growing larger and to keep it from breaking off and traveling to the lungs, which is called a pulmonary embolism.
The treatment happens in two phases. The first, active phase lasts 3 months, and the second phase continues as needed, based on various factors such as the risk of bleeding or of the clot recurring.
In the initial phase, drugs known as anticoagulants, often referred to as “blood thinners”, are administered. These medications include low molecular weight heparin, fondaparinux, or unfractionated heparin, which are all administered for at least 5 days. After this, a type of drug called a vitamin-K antagonist, such as warfarin, is usually prescribed.
Warfarin takes some time to start working, so it is given along with the other anticoagulants until blood tests (known as INR tests) show that it has taken effect. Typically, INR needs to reach a level of at least 2 on two consecutive days. After the first three months, ongoing management will be based on balancing the risks of bleeding with the risks of the clot recurring.
In certain cases, such as when a patient cannot take anticoagulant medications, procedures such as thrombectomy (removal of the blood clot) or placing a filter in the inferior vena cava (IVC), a large vein that carries blood to the heart, may need to be performed.
In cases of portal venous obstruction, a condition where a clot obstructs blood flow in the vein that carries blood from the digestive organs to the liver, doctors typically use a drug known as a ’tissue-type plasminogen activator’ which helps to dissolve clots. Just like before, after this treatment, patients are usually prescribed the blood thinning drug warfarin for at least 3 months.
What else can Vein Obstruction be?
When doctors see signs of conditions involving veins and blood clots, they need to identify the specific problem. Two key issues they look for are:
- Venous thromboembolism, which might be triggered by trauma, swelling (edema), or a skin infection (cellulitis)
- Portal vein obstruction, a blockage of the vein that carries blood from your gut to your liver. This could be due to cirrhosis (liver disease), Budd-Chiari syndrome (a rare liver disorder), or sarcoidosis (an inflammatory disease)
What to expect with Vein Obstruction
With the right treatment, the long-term outlook for patients suffering from venous thromboembolism (VTE), which is a condition where blood clots form in the vein, is positive.
The overall death rate has been found to be less than 10% in cases of chronic pulmonary vein thrombosis, which is when a blood clot remains in the lung’s veins over a long period.
Possible Complications When Diagnosed with Vein Obstruction
Complications from VTE, or blood clots in the veins, can include a life-threatening event known as a pulmonary embolism where a blood clot blocks the main artery of the lung.
Complications from portal vein thrombosis, a blood clot in the liver’s vein, include an unusually large spleen, swollen blood vessels in the esophagus or stomach that may bleed, increased blood pressure in the stomach’s blood vessels, and accumulation of fluid in the abdomen.
Common Complications:
- Pulmonary embolism
- Unusually large spleen
- Swollen blood vessels in the esophagus or stomach that might bleed
- Increased blood pressure in the stomach’s blood vessels
- Accumulation of fluid in the abdomen
