What Is an Embolus? - Definition, Symptoms & Treatment

Instructor: Bethany Lieberman

Bethany is a certified OB/GYN nurse who has a master's degree in Nursing Education.

In this lesson you will learn what an embolus is, what the various causes of embolus formation are and how treatment is targeted at both treating the immediate symptoms caused by the embolus and the underlying condition which caused it to occur.

A Charley-Horse Feeling

Jim was playing racquetball with his friends at the local sports club when he had to sit the last game out due to a cramp in the left calf area of his leg. He showered up, went home and iced his leg, but the feeling still remained. He described the pain to his wife as being similar to a charley horse that just isn't going away. His wife told him to get some rest and sent him to bed. When he woke up the next day, the pain was still there in the same exact spot, but now it was a little red over the area and felt sort of hard to the touch. He could walk and put weight on his leg, but that darned charley horse feeling just wouldn't go away. Jim's wife was sick of hearing him complain and booked an appointment with his physician.

Time for an Ultrasound

Jim's physician took a look at his leg, used a measuring tape to measure the circumference of each calf, and checked his pulses with a hand-held Doppler. He thought Jim may have a condition called deep vein thrombosis (DVT), caused by an embolus in one of the veins in his leg. A deep vein thrombosis occurs when a blood clot causes a blockage in a deep vein of the body and blocks blood flow. The physician ordered an ultrasound and sent Jim to the radiology department for a scan. Yup! The ultrasound confirmed it; Jim had an embolus in the left popliteal (behind the knee) vein in his leg.

What Is an Embolus?

An embolus is the term given to a substance that travels through blood vessels until it reaches a vessel that is too small and becomes stuck. An embolus can be comprised of many different substances, most often it is a piece of a blood clot that has broken off and traveled through the blood stream. It can also be fat, tissue, a product of infection, or an air bubble, since air bubbles are not supposed to be in the blood stream. An embolus can also be a foreign substance, such as a piece of a medical device or a piece of cotton. You might be thinking, how does a person get cotton in the blood stream? Well, take intravenous drug users for example. Before they inject heroin into their veins using a syringe, they filter the heroin through a piece of cotton. Some of the cotton fibers get sucked up into the syringe and accidentally get shot though the blood stream along with the heroin. Yuck!

Emboli, (the plural form of embolus), come in different types; the medical condition resulting from an embolus is called an embolism.

A pulmonary embolism is an embolism that blocks a blood vessel in the lungs. This event can be extremely life threatening, as a blocked vessel in these structures can impede the exchange of oxygen and carbon dioxide.

An amniotic embolism occurs in pregnancy when the amniotic fluid that is produced by the uterus crosses the placenta and travels into the blood stream. It usually gets stuck in the vessels of the lungs and is an emergency, causing immediate need for breathing support for the pregnant mother to prevent death!

An embolism that blocks a vessel in the heart can cause a heart attack from ischemia, or lack of oxygen to the cardiac tissues.

An embolism that blocks a vessel in the brain can cause a stroke by preventing oxygen from reaching the brain tissue. This alters the body's functions which the affected portion of the brain would typically control.


Having an embolus in the leg may cause a feeling of pain, a charley horse-type feeling, or a cramping feeling in the thigh, in the calf, or behind the knee. You may see some changes in color around the area, like redness or bruising, and even swelling may also be present. Serious symptoms of emboli in the heart, lungs, or brain include chest pain, difficult breathing, numbness, weakness, difficulty speaking, or severe headache. These more serious symptoms require immediate medical attention to prevent irreversible tissue damage from lack of oxygen or even death.

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