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Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Hematomas are usually caused by trauma, whether it is the result of a car accident, a minor bump, a cough, or an unknown event. The blood within blood vessels is continually flowing and therefore does not clot or coagulate. When blood leaves the circulatory system and becomes stagnant, there is almost immediate clotting unless the individual is taking anticoagulation medication to prevent blood clots (these may include aspirin, warfarin [Coumadin], clopidogrel [Plavix) and dipyridamole [Persantine]). The greater the amount of bleeding that occurs, the larger the hematoma.

Blood vessels that are fragile may contribute to hematoma formation. For example, an aneurysm or weakening in a blood vessel wall may gradually cause blood vessel cell walls to come apart from constant exposure to the blood flowing and spontaneously leak.

There are many people who take blood thinners or anti-coagulation medications. Examples include warfarin (Coumadin), aspirin, clopidogrel and prasugrel (Effient). These medications increase the potential for spontaneous bleeding and for allowing hematomas to expand because the body cannot efficiently repair blood vessels and blood continues to leak through the damaged areas.

Occasionally, diseases (for example, autoimmune diseases and bacterial infections) may occur that decrease the number of platelets in the blood stream or their ability to function. The platelets are the cells that help initiate blood clot and fibrin formation. If platelets are inhibited, bleeding can continue and hematomas can develop and expand. Examples of bacterial infections and autoimmune diseases include:

• finger infection,
• ankylosing spondylitis, and
• onychomycosis.

All these situations may exist independently to cause a hematoma or two or more may occur together.

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