The onset and progression of decomposition are variable. In temperate conditions, changes begin 24 to 48 h after death.
Hemolysis and generation of hydrogen sulfide gas from anaerobic bacteria such as Clostridium welchii result in the earliest decomposition change, i.e., blue-dark green discoloration in the lower abdominal quadrants (right to left owing to proximity of cecum to skin; see also Fig. 21 and ref. 50). Eventually the entire abdomen becomes discolored, followed by the rest of the body. Seepage of hemoglobin pigments from hemolysed blood and gaseous rupture of blood vessels leads to localized skin discoloration in areas of livid-ity (green, purple, black), mimicking contusions (Fig. 22). "Marbling" refers to an arbore-sent pattern of discoloration due to hemolysis following a vascular distribution (Fig. 23).
° Localized cutaneous discoloration from decomposition mimics antemortem bruises (Fig. 22 and ref. 51). One study tried to resolve this problem. Although hemoglobin pigments filter easily through blood vessels, erythrocyte membranes diffuse less readily because of their molecular size (51). Because bruises are caused by actual disruption of blood vessels, they contain a large amount of erythrocyte membrane (51). Immunohistochemical studies of contusions and postmortem discolorations showed that a positive reaction for glycophorin A, a component of red blood cell membrane, indicated an antemortem injury (51). Glycophorin A was not found in postmortem bruises and was present in only a minority of contusions occurring during life.
° Pre-existent contusions and external hemorrhage are accentuated by hemolysis and diffusion of blood.
° Diffuse extravasation of blood in deeper soft tissues and organs raises the possibility of disease and injury, e.g., diffuse "hemorrhage" in posterior scalp of a supine
Fig. 22. Focal discoloration from decomposition mimics antemortem bruising. Note prominent blood vessels on the livid back. (Courtesy of Dr. M. Moussa, London Health Sciences Centre, London, Ontario, Canada.)
individual suggests trauma; "congested" hemorrhagic lungs (microscopy can even show apparent intra-alveolar edema); pancreatic "hemorrhages" simulating pancreatitis.
° Seepage of sanguinous fluid into body spaces and cavities suggests antemortem injury, e.g., "Hemothoraces" of less than a few 100 mL of sanguinous fluid in each chest cavity are consistent with decomposition; markedly "congested" vessels and thin films of blood in the subdural/subarachnoid spaces, particularly in the occipital lobe area in a supine individual, mimic subarachnoid hemorrhage (Fig. 24). Inspection of the vertex of the brain, after the calvarium is removed, is advantageous because softening from decomposition hinders orientation and examination once the brain is removed.
° Pink teeth occur during decomposition and result from hemolysis of extravasated blood in the dentinal tubules (Fig. 25; refs. 52-57). Postmortem production of carboxyhemoglobin is not a factor (55,57). Cephalic congestion, when it results from a head-down position, and a moist environment (e.g., drowning victim) are factors that promote the development of pink teeth (55-57). Fingernails can also be discolored pink (57). Pink discoloration of teeth is independent of the cause of death (53,56,57). This change is observed within 1 to 2 wk following death (54,56).
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