A contusion or bruise is an area of hemorrhage into soft tissue due to rupture of blood vessels caused by blunt trauma (Figure 4.5). Contusions may be present not only in skin, but also in internal organs, such as the lung, heart, brain, and muscle. A large focal collection of blood in an area of contusion is referred to as a hematoma. A contusion can be differentiated from an area of livor mortis in that, in a contusion, blood has escaped into soft tissue and cannot be wiped or squeezed out, as in an area of livor mortis. The extent and severity of a contusion depends not only upon the amount of force applied, but also on the structure and vascularity of the tissue that is contused. Thus, contusions are more readily incurred in areas with thin, lax skin and in fatty areas.
Contusions might reflect the configuration of the object used to produce the contusion; that is, they might be patterned (Figure 4.6). When an individual is struck with a flat object, such as a board, it is quite common to find parallel linear contusions corresponding to the edges of the board, with normal-appearing tissue in between. A contusion at a site does not necessarily indicate the point of trauma, since soft tissue bleeding will follow the path of least resistance. Deep bruises may not be visible externally and may be
discovered only on incising the soft tissue. In other instances, deep bruises may not become visible externally until hours after death. Scalp bruises are frequently not visible externally unless there is swelling (Figure 12.4). Bruises can also be difficult to detect in dark-skinned individuals.
Contusions, like abrasions, indicate that blunt force has been applied to a particular area. Absence of a bruise, just as absence of an abrasion, does not indicate that there was no blunt force to that area. This is especially true of the anterior abdominal wall, where there may be massive internal injury in the absence of external evidence of trauma. Another point to remember is that a contusion might be much larger than the object that produced it.
As a rule, bruises are not fatal. However, multiple contusions with extensive soft tissue hemorrhage may produce shock and death from massive blood loss. This is seen occasionally in battered children.
The size and severity of a contusion is not always indicative of the amount of force applied, though, obviously, the greater the force, the greater the contusion. Certain factors influence the size of a contusion: age, sex, the condition and health of the victim, and the site and type of tissues struck. Children and the elderly bruise more easily because of loose delicate skin in the former and loss of subcutaneous supportive tissue in the latter. Senile purpura (ecchymoses) on the forearms of the elderly may be mistaken for bruises. Women, especially if obese, seem to bruise more easily. Well-conditioned, muscular individuals are more resistant to bruising. Soft, lax, vascular tissue, such as in the eyelid, is more susceptible to bruising than areas such as the palm. Alcoholics with cirrhosis, individuals with bleeding diatheses, and individuals taking aspirin bleed more easily. A single therapeutic dose of aspirin irreversibly inhibits platelet function for the 7-d life of the platelets with resultant inhibition of hemostasis and a prolonged bleeding time.2
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