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Hematoma

Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Mary Nettleman, MD, MS, MACP

What is a hematoma?

By definition, a hematoma is a collection of blood outside of a blood vessel. It occurs because the wall of a blood vessel wall, artery, vein or capillary, has been damaged and blood has leaked into tissues where it does not belong. The hematoma may be tiny, with just a dot of blood or it can be large and cause significant swelling.

The blood vessels in the body are under constant repair. Minor injuries occur routinely and the body is usually able to repair the damaged vessel wall by activating the blood clotting cascade and forming fibrin patches. Sometimes the repair fails if the damage is extensive and the large defect allows for continued bleeding. As well, if there is great pressure within the blood vessel, for example a major artery, the blood will continue to leak and the hematoma will expand.

Blood that escapes from the blood stream is very irritating and may cause symptoms of inflammation including pain, swelling and redness. Symptoms of a hematoma depend upon their location, their size and whether they cause associated swelling or edema.

Picture of a Blood clot

Bruises and contusions

The medical term ecchymosis is what most people would recognize as a bruise, or blood that has leaked out of a broken blood vessel under the skin that is caused by an injury. Another word for this injury is a contusion. An ecchymosis tends to be flat while a hematoma has more of a three dimensional character to it. As well, hematomas may occur in any organ and not just under the skin.

Hemorrhage

Hemorrhage is the term used to describe active bleeding. The term hematoma describes blood that has already clotted.



Next: What causes a hematoma? »

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Hematoma

What is thrombocytopenia?

Thrombocytopenia is a lower than normal number of platelets in the blood.

Platelets are one of the components of the blood along with white and red blood cells. Platelets play an important role in clotting and bleeding. Platelets are made in the bone marrow similar to other cells in the blood such as, white blood cells and red blood cells. Platelets originate from megakaryocytes which are large cells found in the bone marrow. The fragments of these megakaryocytes are platelets that are released into the blood stream. The circulating platelets make up about two third of the platelets that are released from the bone marrow. The other one third is typically stored (sequestered) in the spleen.

Platelets, in general, have a brief 7 to 10 days life in the blood, after which they are removed from the blood circulation. The number of platelets in the blood is referred to as the platelet count and is normally betw...

Read the Thrombocytopenia (Low Platelet Count) article »











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