Limitations of bruise dating and evidence of antemortem injury
THE CONTEXT
Colour and microscopic findings can help assess bruises, but neither permits confident determination of their exact age.
Variation in appearance and healing
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Bruises in children change colour rapidly and may be absorbed within a few days; healing is very slow in older people.
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Extensive, deeply situated bruising takes longer to become externally visible.
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Subconjunctival ecchymoses receive atmospheric oxygen through conjunctival tissue and do not follow the usual colour sequence. They are initially bright red and then yellow before disappearing.
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A bruise sustained during carbon monoxide poisoning is likely to be bright red.
Microscopic clues and their limits
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Late healing may show large histiocytes containing coarse haemosiderin granules. Haematoidin crystals may remain at the injury site for a long period.
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Exact bruise dating remains difficult even with microscopic examination.
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Loss of red-cell shape and staining characteristics together with iron-containing pigment at the injury site or regional lymph nodes suggests that probably 12 hours have passed since injury.
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Such assessment may help distinguish accident-related cerebral haemorrhage from a pre-existing natural haemorrhage that may have caused the accident.
Antemortem findings and tissue reaction
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Antemortem bruising shows swelling, epithelial damage, extravasation, coagulation, blood infiltration into tissues and colour changes; the source states that these signs are absent in postmortem bruises.
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Contusions and abrasions produced immediately before death show a marked decrease in acidic mucopolysaccharides in connective tissue ground substance, demonstrated by Alcian Blue or the dialyzed iron technique.
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Acidic mucopolysaccharides are absent in contusions more than an hour old and reappear in bruises several days old as connective tissue increases.
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Tissue reaction beyond margination and limited emigration of white cells indicates that a contusion was probably antemortem.