Bruise appearance and factors affecting size and visibility
THE CONTEXT
Bruise size and appearance depend on tissue structure, force, age and other circumstances, so the visible mark does not reflect force alone.
Appearance and size
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Larger, confluent petechiae are called ecchymoses.
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A fresh bruise is usually tender and slightly raised. Even a deep bruise may produce swelling compared with the opposite limb or body part.
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The centre is lighter because impact pushes extravasated blood outward. Most bruises lie in subcutaneous tissues above the deep fascia.
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A Mongolian spot, described as lumbosacral skin hyperpigmentation, should not be confused with a contusion.
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Bruises range from pinhead size to large blood collections. They are slightly larger than the causative object's surface because blood continues to escape into the area.
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Marked surrounding swelling can obscure the original shape. Generally, greater force produces a more extensive bruise.
Tissue characteristics
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Loose, vascular tissues such as the face, vulva and scrotum may develop large bruises after slight violence because they provide space for blood accumulation.
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Strongly supported tissues with firm fibrous tissue and thick dermis, such as the abdomen, back, scalp, palms and soles, may show comparatively small bruises after moderate violence.
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Good muscle tone reduces bruising in boxers and athletes. Bruising is more marked over bone because bone acts as an anvil.
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Scalp bruises are better felt than seen, and a fluctuant centre may simulate a depressed fracture.
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Resilient areas such as the abdominal wall and buttock bruise less.
Circumstances affecting visibility
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Chronic alcoholics bruise easily.
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Bruising may not be visible when the injured part is thickly covered or the weapon is yielding, such as a sandbag.
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Bruising may be absent when pressure continues until death. Severe injury may produce little haemorrhage if preceded by an injury causing deep shock.
Effect of age
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Children bruise easily because of softer tissues and loose, delicate skin.
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Older persons bruise easily because of loss of subcutaneous tissue and flesh, together with cardiovascular changes.