Thrombosis: Causes, Symptoms, Types, Diagnosis, Treatment, Prevention and Overview

A thrombus is a blood clot in the vascular system (circulatory system). It remains attached to the site where it was formed and prevents blood flow.

In these circumstances, a person is said to be experiencing a thrombosis.

A thrombus is more likely to occur in people who are immobile and who are genetically predisposed to blood clotting . A thrombus can also form if a surrounding artery, vein, or tissue is damaged.

A blood clot is generally a healthy physical response to injury. It quickly forms a plug that can reduce or even prevent bleeding. A little bit of blood clot that breaks free from the thrombus site and circulates in the bloodstream is called an embolus.

An embolus moves through the vascular system until it is finally lodged. An embolus is a dangerous and life-threatening complication of thrombosis, especially if the embolus reaches the heart, lungs, or brain.

When this happens, the person is said to be experiencing a stroke.

The effect of a thrombus in the body depends on its location. When a thrombus forms in an artery, such as in the heart or brain, it is called an arterial thrombosis.

When a thrombus occurs in a vein, it is called a venous thrombosis. When this happens in the deep veins of the leg, it is called a deep vein thrombosis (DVT).

Causes of thrombosis

Clotting is caused by chemical reactions between blood cells (platelets) and proteins (clotting factors). A healthy body regulates the clotting process when the body needs it.

When any of the following are present, a clot can more easily form inside a blood vessel:

  • Smoke tobacco.
  • High cholesterol.
  • Being obese or overweight.
  • Cancer.
  • Mellitus diabetes.
  • Stress .
  • Not exercising (sedentary lifestyle).

Some of these factors also increase the risk of atherosclerosis, a condition in which the blood vessels become clogged with deposits of fatty plaque. Atherosclerosis increases the risk that blood clots will block arteries and veins.

Venous thrombosis

A venous thrombosis is classified as a thrombus (blood clot) that has formed in a vein. Veins are the blood vessels that (usually) carry blood away from the heart.

Blood can flow more slowly in veins than arteries, and this can increase the likelihood that blood clots will form in these vessels. However, other factors also increase a person’s chances of developing a venous thrombosis.

Venous thrombosis can be caused by:

  • Disease or injury to the veins of the legs.
  • Not being able to move (immobility) for any reason.
  • A broken bone (fracture).
  • Certain medications
  • Obesity.
  • Hereditary disorders.
  • A higher chance of having a certain disorder based on your genes.
  • Autoimmune disorders that make the blood more likely to clot.
  • Medicines that increase the risk of clotting (such as certain contraceptive medicines).

Venous thrombosis is classified as:

Superficial vein thrombosis: A superficial vein is a vein that is close to the surface of the body. They are generally responsible for helping cool the body. It is possible to see these bulging veins under certain conditions.

Patients may feel an area slightly harder or witness some redness of the area. These thromboses are usually not as serious as deep vein thrombosis; however, they can become more serious if it enters the deep veins through the perforating veins.

Deep vein thrombosis : occurs within the deep veins, which are further away from the surface of the skin. More blood is transported through deep vein systems than through superficial veins.

Blood clots can form in deep blood vessels, most commonly in the legs and groin, and can block normal blood flow back from the legs to the heart.

Most deep vein thromboses occur within the legs, although they can occur anywhere within the deep vein system.


Arterial and venous thrombosis can reduce or totally prevent blood flow. This can lead to serious and even life-threatening complications, depending on where the thrombus forms .

A thrombus usually doesn’t cause any symptoms until it blocks or severely restricts blood flow. The symptoms and complications of each type of thrombus are described below.

Arterial thrombosis

A thrombus in an artery can cause:

  • Unstable angina, a type of chest pain.
  • Heart attack.
  • Ischemic stroke.
  • Ischemia of the peripheral arterial extremities, where blood flow to the extremities is significantly reduced.

All of these conditions require immediate medical attention. People should seek emergency treatment if they experience any of the following symptoms:

  • Chest pain.
  • Difficulty breathing.
  • The lower half of the face slopes down on one side.
  • Sudden loss of strength in an arm or leg.
  • A limb that has turned cold, pale, and painful.

Venous thrombosis

A thrombus in a vein, usually a vein deep in the leg, can cause the following symptoms:

  • Pain, swelling, and tenderness, usually in the calf.
  • A sore and warm feeling on the skin in the affected area.
  • Red skin, particularly on the back of the leg below the knee.

People experiencing any of these symptoms should see a doctor. A deep vein thrombosis (DVT) can be a life-threatening condition. Blood clots can break loose and travel through the bloodstream before eventually blocking arteries higher in the body.

An ultrasound is usually required to help provide a definitive diagnosis. People who are considered to be at higher risk of developing this type of thrombosis are advised to move frequently and perform calf exercises to promote better blood flow to the area.

Those who cannot exercise can be given graduated compression stockings or blood thinning medications such as warfarin or heparin.

Other types of thrombosis are:

Renal vein thrombosis (TVR) : A renal vein thrombosis is a thrombosis that occurs in the veins that drain blood away from the kidneys. These clots reduce the kidneys’ ability to clean and filter the blood. This can increase the risk that more clots will develop later.

Renal vein thrombosis should be treated as soon as it is discovered to help keep kidney function stable. Men are twice as likely to have renal vein thrombosis (TVR) as women, although the reasons for this are largely unknown.

Venous thrombus embolism (VTE) : Your symptoms depend on the location of the affected vessel and whether the vessel is totally or partially occluded by the clot.

Venous clots that form in regions of slow to moderate flow are made up of a mixture of red blood cells, platelets, and fibrin and are known as mixed platelet fibrin thrombi.

Pulmonary embolism (PE) : Pulmonary embolism (PE) is the result of part or all of a blood clot breaking loose and being carried through the bloodstream to the lung where it obstructs the blood vessel.

The size of the clot and the site of the obstruction of blood flow in the vessel determine the extent and severity of the pulmonary embolus.

Proximal vein thrombosis is more likely to lead to fatal pulmonary embolism (PE) compared to calf vein thrombosis.

The incidence of a fatal pulmonary embolism can be markedly reduced if deep vein thrombosis (DVT) is treated with anticoagulant therapy.

Superficial thrombophlebitis : Superficial thrombophlebitis is due to blood clots that form in veins that are closer to the surface of the skin and are associated with inflammation.

Superficial thrombophlebitis is often seen in individuals who are heterozygous or homozygous for the factor V Leiden mutation.


Doctors use several different methods to diagnose the effects or presence of thrombus formation.

  • Duplex ultrasound is the most common test to diagnose deep vein thrombosis (DVT). This method uses sound waves to create images of the blood flowing through the arteries and veins.
  • A dimer test measures a substance in the blood that results when a blood clot breaks down. If the test shows high levels of the substance, then there may be a deep vein thrombosis or some other type of blood clot, but this is not certain.

If the test result is normal and there are few risk factors, deep vein thrombosis is considered unlikely.

  • Venography involves a dye injected into a vein in the affected leg. This dye makes the vein visible on some types of x-rays, such as a fluoroscopy. If this shows that blood is flowing more slowly than normal in the vein, it may indicate the presence of a thrombus.
  • Magnetic resonance imaging (MRI) and CT scan create images of organs and tissues, and they can also be used to look at blood vessels.
  • A VQ scanner is a nuclear imaging study that shows the flow of air and blood within the lungs.
  • Blood tests can be used to detect an inherited blood clotting disorder. This may be necessary in cases of repeated but unexplained blood clots.

Thrombi found in the liver, kidney, or brain can also be due to an inherited bleeding disorder.

Treatment of thrombosis

The objective of treatment with thrombi is quickly and effectively, for this it is necessary to:

  • Control symptoms.
  • Restore blood flow.
  • Reduce and remove the thrombus.

The following treatments are generally used to treat the effects of thrombi:


Surgery for the effects of thrombosis will always be a medical emergency. It can involve direct access and unblocking of an affected artery.

In other cases, blood flow will bypass or go completely through the blocked artery.

Lower vena cava filters (IVC)

Inferior vena cava filters are small mesh devices placed in the inferior vena cava, which is a large vein, usually under local anesthesia. The inferior vena cava (IVC) filter traps the blood clot fragments and can prevent them from reaching the heart and lungs.

An inferior vena cava filter (CVI) can be permanent and is usually combined with anticoagulant medication therapy when possible. However, doctors can remove the inferior vena cava (IVC) filter after the risk of a blood clot has been reduced.


They can reduce the chance of blood clots, and this can reduce the size of the blood clots.

If blood thinners don’t work, or if the person taking them is intolerant of them, doctors will consider other treatments.

Compression socks

Doctors may recommend that people wear compression stockings while taking anticoagulant therapy for deep vein thrombosis (DVT).

Stockings help prevent calf pain and swelling, and reduce the risk of complications.

A person should wear compression stockings during the day for as long as their doctor recommends.

Raising the affected leg

Along with compression stockings, it is good to keep the legs affected by thrombi raised at night so that the foot is higher than the hip. This relieves pressure in the veins, improves blood circulation, and can help prevent complications.


Once a doctor has prescribed compression stockings, they will usually advise people to stimulate blood circulation by walking or exercising more often.


It is not always possible to prevent a thrombus from forming. However, there are steps people can take to reduce their risk:

  • Avoid or quit smoking tobacco products.
  • Maintaining a healthy weight.
  • Following a healthy diet.
  • Get regular exercise.

It is particularly important for people to get up and move when possible after a surgical procedure or during long-distance travel.

Those known to be at increased risk of developing a blood clot can also receive anticoagulant therapy, as well as medications to lower blood pressure and blood cholesterol levels.


If a person receives the right treatment at the right time, even the potentially fatal medical emergencies associated with thrombosis can be successfully treated.

Aftercare is of particular importance because complications can develop months or even years after thrombus formation, even after successful treatment.

The post – thrombotic syndrome is one of the potential complications of deep vein thrombosis (DVT). This refers to damage to the surrounding tissue caused by the formation of deep vein thrombosis (DVT), such as increased pressure in the vein when blood flow is blocked, ulcerations, and pain.

This can cause permanent damage and, in rare circumstances, the limb may need to be removed.

Recovery depends on the location of the clot, as well as how much and for how long blood flow was interrupted. The sooner the condition is treated, the less likely long-term damage or complications are to develop.