Page 587 - The Veterinary Laboratory and Field Manual 3rd Edition

524 Samuel Sharpe

A2.9 Post-mortem artefact or containing large amounts of bacteria (GI
tract) will autolyse more rapidly. In addition,
Post-mortem artefacts that occur as a result autolysis will proceed more rapidly in warmer
of tissue degradation and decomposition can ambient temperatures and in larger animals or
mimic lesions and confuse the unsuspecting pro- animals with large amounts of adipose tissue,
sector. It is not uncommon to receive samples heavy fleece or hair coat which will cool more
at the lab from veterinarians in the field along slowly than smaller carcasses. Affected tissues
with necropsy reports of their gross findings will lose structure and appear soft and in later
which consist entirely of misinterpreted artefac- stages become entirely liquefied. Even at this
tual lesions. The next section will describe the stage it is not an entirely lost cause to collect
appearance of several of the most common post- tissues for histopathology as it may be possible
mortem artefacts so that if they are encountered to discern some important features even if most
during a post-mortem they can be identified and tissue detail is lost. Furthermore, molecular test-
discounted. ing (for example, PCR) can still be attempted
on autolysed tissue although sensitivity will be
reduced. Autolysed tissue is not appropriate for
autolysis bacterial culture as the tissue will be heavily
contaminated with bacteria which have invaded
After death, proteolytic enzymes within tissues post-mortem making interpretation of the sig-
along with bacterial action cause the breakdown nificance results impossible.
of tissues (Figure A2.11). Tissues with high
levels of proteolytic enzymes (kidney and liver)
cloudy cornea

Transparency of corneas is maintained by the
constant removal of water by active transport.
After death, this process ceases and fluid enters
the cornea by osmosis resulting in gradual opac-
ity. This process will be hastened if the carcass
has been frozen and thawed prior to exami-
nation. It should be differentiated from true
corneal stroma oedema or scarring. Samples
should be submitted for histopathology if it is
unclear whether this represents a true lesion.

Figure A2.11 Kidney, bovine. Autolysis. Autolysis
occurs more rapidly in organs containing higher Hypostatic congestion
levels of proteolytic enzymes such as the liver and
kidney or that contain large amounts of bacteria After death, blood will pool by gravity onto the
such as the GI tract. In this case the kidney is pallid dependent side of the carcass. This can occur in
and has lost structure appearing diffusely softened. any organ including the skin and skeletal muscle
Note also fine emphysematous gas bubbles in the but is most pronounced in well-vascularized tis-
tissue. See also Plate 50. Photo: courtesy of Mr R. sues with abundant, loose connective tissue such
Irvine, University of Glasgow, UK. as the lung (Figure A2.12). It must be differen-

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