Assessing trauma in frozen carcasses: Freeze artefact in New Zealand fur seals

Freezing and thawing of cadavers prior to post-mortem examination is widely known to cause tissue artefact, but there appear to be no published studies in the veterinary literature describing these findings. This study compared gross findings in frozen (n=5) and chilled (n=5) New Zealand fur seals (Arctocephalus forsteri) that had been incidentally captured during fishery operations. Subcutaneous bruising, renal capsular haemorrhage, and bloody abdominal fluid (<50– 380 ml) were present in 5/5 frozen fur seals; none of the chilled fur seals had these lesions. In addition, 3/5 (60%) frozen fur seals had focal, dark-red discolouration of the surface of the brain, which could readily be interpreted as brain contusion; none of the chilled animals had this lesion. Thus, freezing and thawing of pinniped cadavers can induce artefacts which mimic traumatic lesions. Consideration of this possibility is vital in any necropsy study using previously frozen tissues.