What is The Difference Between a Blood Clot and a Hematoma

Find out what the difference is between a blood clot and a hematoma.

This question gets raised quite often in the article What is a Hematoma and I haven’t fully answered the question there, which is the point of this article. Really there isn’t much of a difference between a blood clot and a hematoma and the terms are sometimes interchangeable depending on the circumstances and injury. Simply put a blood clot is coagulated (hardened) blood that serves a purpose to protect a damaged blood vessel whereas hematoma is coagulated blood that has seeped into the surrounding tissue and serves no purpose. A detailed explanation on these two different occurrences can be found below.

Definition of a Blood Clot

A blood clot is generally defined as a blockage caused by blood collecting in one place; normally in a vein or artery. A blood clot forms when the wall of a blood vessel has been breached. When the wall is torn open blood begins to spill out into the surrounding tissue and can form a hematoma (see below). The body’s response to this damage is to send in platelets that stick to the damaged area to form a loose plug. Clotting factors then activate to form strands called fibrin that hold the platelets together. White and red blood cells get caught in the new mesh to form a sealed clot; this process is known as coagulation. If too much coagulation occurs then you end up with a blocked blood vessel, in normal circumstances this is prevented by coagulation inhibitors that control the size of the clot. Once the blood vessel has restored itself the clot is then dissolved by the body and the vessel returns to normal.

Blood clot diagram (Thrombus) (Photo credit: Wikipedia)

Definition of a Hematoma

A hematoma is a collection of coagulated blood (bruise) that has seeped into the surrounding tissue. In the section above we talk about how a clot is formed when a blood vessel is damaged; it is in the initial stages that a hematoma is formed. If the damage is significant enough, or if the body is slow to react to the injury then blood will continue to seep out in to the surrounding tissue. The blood flow will only cease when the blood vessel wall has been closed off by the platelets and fibrin. Once the blood has coagulated (hardened) the body will slowly begin to dissolve it. 

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