Tumour or haemorrhage?: Differential diagnosis of an unknown mass within the brain of a budgerigar (Melopsittacus undulatus) using a novel imaging pipeline.

We report on a previously healthy zoo specimen of an adult budgerigar (Melopsittacus undulatus, obtainedwithpermission fromSouthwick'sZoo) founddeceased in its enclosure. To assess cause of death and ensure the absence of an infectious neoplasia, we used an integrated multiscale brain-imaging workflow, previously only used on mammals. The specimen was imaged with microcomputed tomography before and after enhancing soft-tissue contrast with diffusible iodine-based contrast-enhanced microcomputed tomography. Scans revealed an orbital blowout fracture and an unidentified large mass across majority of the diencephalon, striatum and midbrain caudal to the right orbit. After destaining, neural pathohistology confirmed the mass as a brain haemorrhage with no evidence of neoplasia or inflammation. We conclude that this specimen died of head trauma, likely from a head-on collision within its enclosure. This multiscale imaging workflow (diffusible iodine-based contrast-enhanced microcomputed tomography followed by destaining and pathohistology) can improve our evaluation of differential diagnoses in avian specimens. [ABSTRACT FROM AUTHOR]