When blood collects outside the veins or arteries, the result is a hematoma. Bruises and so-called “blood blisters” are common examples of a hematoma. Most often, hematomas resolve themselves over several days with no adverse effects.
Sometimes, however, a hematoma can be dangerous and require medical intervention.
Subdural or epidural hematomas, or hematomas within brain or spinal tissue, can be particularly dangerous. The swelling associated with hematomas in these locations can cause damage to the brain or nerve tissue. Doctors may have to intervene surgically to drain the hematoma in order to reduce swelling in the area.
A hematoma in the abdominal cavity happens when internal bleeding begins to clot. This can result in intestinal blockage or infection and lead to serious complications. Blood clots in the urine or stool may indicate the presence of a dangerous abdominal hematoma.
Any bruise or other hematoma of the skin that increases in size over time could also present a danger. If a clot from a hematoma reenters the bloodstream, it can block an artery, cutting off blood flow to part of the body. Without prompt treatment, this can result in permanent tissue damage.
It can be beneficial to have a physician look at any contusion or internal bleeding to ensure that a dangerous hematoma is not present, and to monitor bruises to ensure they are healing properly.