Post-Mortem Computed Tomography Pulmonary Findings in Harbor Porpoises (Phocoena phocoena)

Abstract

The application of whole-body post-mortem computed tomography (PMCT) in veterinary and wildlife post-mortem research programs is advancing. A high incidence of pulmonary pathology is reported in the harbor porpoise (Phocoena phocoena). In this study, the value of PMCT focused on pulmonary assessment is evaluated. The objectives of this study were to describe pulmonary changes as well as autolytic features detected by PMCT examination and to compare those findings with conventional necropsy. Retrospective evaluation of whole-body PMCT images of 46 relatively fresh harbor porpoises and corresponding conventional necropsy reports was carried out, with a special focus on the respiratory tract. Common pulmonary PMCT findings included: moderate (24/46) to severe (19/46) increased pulmonary soft tissue attenuation, severe parasite burden (17/46), bronchial wall thickening (30/46), and mild autolysis (26/46). Compared to conventional necropsy, PMCT more frequently identified pneumothorax (5/46 vs. none), tracheal content (26/46 vs. 7/46), and macroscopic pulmonary mineralization (23/46 vs. 11/46), and provided more information of the distribution of pulmonary changes. These results indicate that PMCT adds information on pulmonary assessment and is a promising complementary technique for necropsy, despite the frequent presence of mild autolytic features.

Keywords: cetacean; decomposition; necropsy; pulmonary pathology; virtopsy.

Figure 1

Examples of autolysis score on PMCT. From left to right: (A) mild: PSTA (pulmonary soft tissue attenuation) present in less than 25% of the lung parenchyma, (B) moderate: retraction of the lung margins with presence of gas in the pleural space and 25–70% of PSTA noted, and (C) severe: gas attenuation presence in vascular structures and other visible soft tissue structures, over 75% of PSTA present.

Figure 2

Intraluminal tracheobronchial tubular structures’ severity score on PMCT. (A) Absent, (B) mild: few parasites present, filling less than 25% of the bronchial lumen, (C) moderate: filling 50–75% of the bronchial lumen, and (D) severe: parasites present up to the level of the trachea, almost complete occlusion of bronchial lumen.

Figure 3

Pulmonary soft tissue attenuation score on PMCT. Clockwise presentation of: (A) mild: minimal focal, heterogeneous PSTA affecting <30% of the lungs, (B,C) moderate: diffuse, heterogeneous PSTA, including focal homogeneous PSTA affecting 30–75% of the lung parenchyma, and (D) severe: diffuse, homogeneous PSTA, affecting >75% of the lung parenchyma.

Figure 4

Example of an asymmetric gradient of pulmonary soft tissue attenuation found on PMCT, with signs of associated thoracic wall flattening on the left side of the image, likely consistent with positional-dependent hypostatic edema.

Figure 5

Two PMCT patterns of pulmonary mineralization. (A) Singular medium to large irregular shaped mineral attenuating areas, associated with a (nodular) consolidated region. (B) Multifocal distributed pinpoint mineral attenuating foci throughout the lung parenchyma.

Figure 6

Patterns of pulmonary air entrapment on PMCT. From left to right: (A) Peripheral bullous bronchiectasis, (B) diffusely distributed small, rounded gas attenuations throughout the pulmonary parenchyma, including the vasculature, and (C) mosaic pattern with peripheral areas of decreased parenchymal attenuation.