05: Postmortem Autolysis

Postmortem autolysis looks a lot like what type of necrosis

Gangrenous necrosis

Why is postmortem autolysis annoying

If it is severe, it can mask any real lesions that may have been present

Antemortem lesion

Changes in cells that happened while the animal was alive

Postmortem lesion

Changes in cells that happened after death

Autolysis

Self digestion due to decay

Postmortem decomposition

Changes due to bacteria and autolysis

Factors that affect autolysis

• Temp (internal or ambient)

• BCS

• Bacteria

Would a small intestine undergo faster or slower autolysis

Faster → lots of bacteria

Would an over conditioned black angus in summer undergo faster or slower autolysis

WAY faster → black fur in summer means it’s hot, and the fat means the heat is well retained

Putrefaction

Breakdown of tissued by bacterial enzymes

Gross features of putrefaction

Soft and foul-smelling tissues

If you see an area with lots of bacterial decay, how can you tell if it was antemortem or putrefaction

If there is lots of bacteria but no inflammation, it is likely a postmortem change

Rigor mortis

Process where muscles stiffen due to low ATP

When does rigor mortis usually set in

1-6 hours postmortem

When does rigor mortis usually go away

24-48 hours postmortem

Bile imbibition

Scalding due to contact with leaking bile

Gross features of bile imbibition

Orange-yellow-green discoloration (near the gall bladder!)

Hemoglobin imbibition

Postmortem RBC breakdown, commonly in endothelium and endocardium

Gross features of hemoglobin imbibition

Pink-orange discoloration

Hypostatic congestion

Blood pooling, often in paired organs

Gross features of hypostatic congestion

Dark red pooling in the “down-side” organs

Why is hypostatic congestion tricky

Can be an antemortem problem too

What postmortem change happens to aborted fetuses in utero

Autolysis

Pallor

Pale discoloration due to pooling or bacteria

Pseudomelanosis

Gray/black discoloration due to hydrogen sulfide from bacteria

Gross features of gas accumulation

• Organ distension

• Postmortem emphysema

• Distension of subcutis

Why is gas accumulation a tricky postmortem finding

It can be antemortem too

How can you differentiate between antemortem and postmortem gas distension

• Check for organs that are out of place

• See if necrosis has started → could indicate antemortem damage

Types of postmortem clots

• Yellow “chicken fat” clots

• Dark red “jelly” clots

Why are there two types of postmortem clots

The RBCs settle from the plasma

How can you tell if a rupture happened ante/postmortem

If there is hemorrhaging on the edges, it was antemortem

Signs of advanced decomposition

• Holes

• Dehydration/mummification

• Invasion of insects

Situations where samples with advanced decay may still be run

• Legal cases

• Prohibitive weather extremes

• Prohibitive cost

• Delayed decision to necropsy

Key things to do if you end up doing a veterinary forensic analysis

• Take photos of everything

• Take notes, sign and date them

• Refer to a diagnostic laboratory