Extravasation of blood into the tissues due to rupture of capillaries, venules and small arterioles usually as a result of trauma, is called a bruise.
Types of Bruises
Depending on the location, bruises are classified into:
- Subcutaneous bruises
- Intradermal bruises
- Deep bruises or contusions
- Blunt trauma is the common cause of bruising, e.g. with stick, stone, stick or fist.
- Pathological bruising may also occur due to trivial trauma, as in hemophilia and other bleeding disorders.
Bruises often co-exist with abrasions and lacerations. The degree of violence required to produce bruise varies from firm gripping to heavy blows, depending on many other factors.
Factors Affecting Bruising
1. Tissue type
Loose connective tissue type sites e.g. eye, face, genitalia, show more bruising. Bruises are also more marked in sites overlying bones, but are rarely seen on the scalp, palms or soles.
2. Severity of Trauma
More severe is the trauma, more bruising occurs
Infants and elderly bruise easily. Infants have loose and delicate skin while elderly have lost elasticity of skin and blood vessels
Women bruise more easily than me
5. Skin color
Fair skinned persons have more obvious bruises
Blood dyscrasias, hypertension patients bruise more easily.
7. Gravity Shifting
Fascial planes more prevent blood from torn vessels to reach the surface, thus bruise appears in remote areas. E.g.
- a person having fracture of upper end of humerus may show bruising in elbow
- a person hit on forehead may show bruising over eyes (Spectate hematoma, black eye)
- fall on the vertex –bruise may be behind the ear (Battle’s sign)
Aging of Bruise/Color Changes
These are due to degradation products of blood.
|Blue||24 hours||Deoxygenated hemoglobin|
|Bluish black||2-4 days||Hemosiderin|
Exception is subconjunctival hemorrhage (or bruise, black eye) which follows the following sequence:
Red –>Yellow –> Disappears
Yellow color or yellow tinge in a bruise does not appear before 18 hours. In regions of dense fatty tissue e.g. back, bruise does not appear quickly and is also slow to disappear.
Characteristics of Bruise
- Bruises may not always show at the original impact site due to gravity shifting
- Size of the bruise may not necessarily commensurate with the severity of trauma
- Deep bruises may take 1-2 days to become visible externally, therefore re-examination after 1-2 days is recommended
- Deep bruises may never show up externally (e.g. in vehicular accidents). Deep incisions at autopsy are necessary to demonstrate them.
- Nature of trauma i.e. blunt
- Indicator of antemortem nature
- Site of trauma (Gravity shifting must be kept in mind)
- Degree of violence
- Identity of weapon
- Time of injury
- Purpose of injury
- Whether homicidal, suicidal or accidental
Conditions Simulating a Bruise
- In dead –hypostasis
- In living –irritant skin lesions
Differentiating Bruise from Hypostasis
|Due to engorged vessels, extending into dependent epidermal vessles||Due to ruptured vessels, which may or may not be located deep|
|Situation is on dependent parts only||Can be situated anywhere|
|Has clearly defined margins which are horizontal||Margins diffusely merge with the surrounding area|
|There is no swelling and no abrasions||Swelling and abrasions may be present|
|If a cut is made, blood oozes out which can be washed easily||If a cut is made, blood oozes out which cannot be washed easily|
|No inflammatory evidence on microscopic examination||Always evidence of inflammation|
|Uniform color||May be variegated in color|
|Blood elements are found within blood vessels||Blood vessels are found outside blood vessels|