Two-Dimensional Topographic Description of the Small Cetacean Liver and Adjacent Structures For Ultrasonographic Examination
Real-time ultrasonography is routinely used at present in the clinical
protocols for veterinary practice, being considered a very useful method for detecting hepatic
lesions in terrestrial mammals. The lack of specific examination protocols and two-dimensional
topographic descriptions of small cetacean internal organs represents the main limitation for
using ultrasonographic examination in these species.
Some ultrasonographically detectable hepatic lesions have been described
post-mortem in marine mammals, including tumours, abscesses, cysts, lipidosis, and parasites,
thus ultrasound examination could be considered as a useful diagnostic tool "in vivo" of
these lesions. Moreover, a good anatomical knowledge of the liver topography and the adjacent
organs will be essential for ultrasound guided fine-needle biopsies. The aim of this
presentation is the description of the small cetaceans liver location in a plane-section format
for an easy application to the imaging diagnostic methods, especially real-time ultrasonography.
For this purpose, three fresh carcasses of dead stranded common dolphins and
one striped dolphin positioned in ventral recumbency were frozen in a box with water forming an
ice block for a better parallel slicing. The dolphins were cut using an industrial saw in one
centimetre thick transversal (two common dolphins), sagittal (one striped dolphin) and coronal
sections (one common dolphin). Every body section was photographed and pictures were digitalized
for full computer analysis and description.
Moreover, twenty-five animals, including dead and live dolphins belonging to
four different species (common dolphin (18), striped dolphin (3), harbour porpoise (3) and a
pilot whale calf) were ultrasonically examined using a real-time scanner with a 3'5 MHZ
transducer. Transducer positioning was tested in live animals looking for best quality images:
underwater keeping the animal in a natural position and out of the water after removing the
dolphin from the pool.
Computed axial tomography and magnetic resonance imaging of the entire body
was also performed in a dead common dolphin.
The description and comparison of the different imaging methods applied and
the dolphin body sections becomes a very helpful tool improving the knowledge of visceral
topography. All these data represent a two-dimensional anatomical description of the dolphin
liver, boundaries and structure, being a first step towards including ultrasonographic
examination of this main organ in the clinical guidelines of diagnosis in small cetaceans.