Postmortem Abdominal Ultrasound in Healthy Wild Mammals for Application in Forensic Veterinary Medicine

Diagnostic imaging methods have been used in human medicine to identify and examine cadavers to determine the cause of death. In veterinary medicine, the use of these resources is still scarce and little known, and it is necessary to establish the contribution that methods such as ultrasound could provide to the investigation of the cause of death in domestic and wild animals. Postmortem ultrasonography (PMUS) can help forensic science find injuries that even in conventional necropsy go unnoticed. Thus, knowing the sensitivity and accuracy of the method is important and, therefore, the present study aimed to evaluate the applicability of the technique and describe the abdominal ultrasound findings in carcasses of wild mammals that died of natural causes and in different states of autolysis. Considering that wild animals are often found in adverse situations, such as the time elapsed before they are discovered, the conservation temperature and environmental conditions that may mask the true state of autolysis, and since ultrasound is portable, this tool becomes important for the forensic expert's decision-making. Thus, we hypothesise that the application of PMUS is an important alternative for establishing the thanatological state (TS) and the conditions for performing conventional necropsy. The choice of wild mammals was made due to their similarity with domestic mammals, which facilitates the search for literature and standards. Animals received by the Instituto de Criminalística Nacional (National Forensic Institute) of the Federal Police of Brazil were used. Eighteen wild mammal carcasses were examined, in varying autolytic states: three pumas (Puma concolor), three jaguars (Panthera onca), two South American coatis (Nasua nasua), two giant anteaters (Myrmecophaga tridactyla), two white opossums (Didelphis albiventris), one pampas deer (Ozotoceros bezoarticus), one capybara (Hydrochoerus hydrochaeris), one maned wolf (Chrysocyon brachyurus), one black-eared opossum (Didelphis aurita), one tayra (Eira barbara) and one tapeti (Sylvilagus brasiliensis). The accuracy and sensitivity of the ultrasound examination were observed in four TSs: zero 0 (intact), I (mild autolysis), II (moderate autolysis) and III (marked autolysis). The ultrasound evaluation was more sensitive for TS 0 and I; however, it was still possible to evaluate the liver, spleen, kidneys, small intestine and urinary bladder in advanced TS (II and III). The greater the degree of autolysis, the fewer structures and details were visualised. It was concluded that intact or discretely autolysed wild mammals are the most suitable for evaluation by postmortem ultrasound and kidneys and gallbladder were the main structures visualised in cases with advanced autolysis (TS II and III). The findings of this study should be considered preliminary, given that the sampling design was heterogeneous and comprised a limited number of individuals per species.