What Is the Difference Between Thrombus and Embolism?

Thrombosis and embolisms are blockages in the blood vessels that require immediate medical treatment. A thrombus occurs in the legs, pelvis, arms or heart while an embolism occurs in the lungs.

Thrombosis and embolism are obstructions that form in your vascular system and require immediate medical attention. Without treatment, you could end up losing critical blood flow that deprives you of oxygen and leads to sudden death. The damage caused by both forms of blockages can cause your blood vessels to narrow. 

Understanding the differences between the two conditions and distinguishing the symptoms can help you understand the steps that should be taken to treat them. The main way to determine whether a blood clot is a thrombus vs. an embolism is where they form in the body.

What is thrombus?

Deep vein thrombosis (DVT) is a medical disorder where people develop blood clots in their veins. The blockage that forms is called a thrombus. They can be found in different parts of your body, including your thigh, lower leg, pelvis, and arm.

There are two main types of thrombosis:  

• Venous thrombosis — Caused by a blood clot forming in and blocking blood flow in a vein.
• Arterial thrombosis — Caused by a blood clot forming in an artery responsible for carrying blood from and to the heart. Some typical causes of arterial thrombosis include hardening because of a buildup of fat and calcium deposits in the artery walls. That causes plaque to form that can rupture suddenly and lead to a blood clot.   

What is an embolism?

A pulmonary embolism (PE) forms when there is a blockage in one of your lung arteries. They are often the result of a blood clot breaking off from a DVT and getting carried through the bloodstream into your lungs. 

While thrombi and embolisms are connected, they typically manifest different symptoms. These symptoms may not occur all at once. Some people have no symptoms at all after developing a thrombus or an embolism. 

Symptoms of a thrombus

People with a thrombus may show signs like:

• Swelling in the affected limb
• Pain and tenderness in the area of the thrombus
• See distended veins
• Have red or discolored skin
• Have a vein that feels firm or thick  

Symptoms of an embolism

Fifty percent of people with a pulmonary embolism show no symptoms. Those who do may display signs like: 

• Shortness of breath
• Chest pain
• Dizziness or fainting
• Heart palpitations
• Coughing up blood
• Pain and tenderness in the area of the blood clot

There is a direct link between the formation of a thrombus and an embolism. 

Causes of a thrombus

Anyone can end up with a DVT. The following risk factors can make you more likely to develop a thrombus, like:   

• Living a sedentary lifestyle where you do not move around frequently
• Recently having surgery
• Breaking a bone
• Bedridden because of an illness
• Traveled a long way, like in a car or airplane
• Being a smoker who is 60 years or older

Certain medical conditions or diseases can make you more vulnerable to DVT and related thrombus, like:

• Heart disease
• Stroke
• Paralysis
• High blood pressure
• Surgery
• Cancer treatment
• Hormone treatment like birth control or HRT
• Pregnancy

Causes of an embolism

Various factors can increase your risk of developing a pulmonary embolism, like: 

• Taking medications with hormones
• Having a broken bone
• Having a family history of thrombus and PE
• Being medically obese

Suppose you have no obvious symptoms of a thrombus or an embolism. In that case, you likely won’t know that you have either condition unless there is a medical emergency that leads to its discovery. If you exhibit symptoms of a thrombus or an embolism, it’s a good idea to have yourself checked out by a doctor. 

Physicians typically start by going over your medical history and then performing a physical exam. They may also decide to order additional testing if they suspect that you have a thrombus or an embolism, including: 

• Ultrasound — A procedure which uses sound waves to evaluate the blood flow in your veins and arteries
• Blood tests — A procedure done to check the how well your blood clots
• Venography — A procedure in which dye is injected into the vein before an x-ray so that doctors can examine your blood flow and check for blood clots

Doctors typically base treatment plans for thrombosis and embolism on factors like: 

• Medical history
• The severity of your illness
• Your age
• Your ability to handle different therapies, medications, and treatments

Treatments often provided to patients with a thrombus include:

• Taking a blood-thinning medication
• Inserting catheters to widen the affected blood vessels
• Placing a stent inside a blood vessel to keep a blood vessel from closing

Your physician may also recommend other preventative measures to keep you from developing a thrombosis or embolism, like:

• Making lifestyle changes like giving up smoking or eating healthier
• Wearing compression socks to stop the development of DVT
• Getting regular checkups
• Making sure you stand up and move after sitting for long periods
• Moving around when it is safe after surgery or lengthy bed confinement because of illness