Ultrasonography plays an important role in modern-day cetacean preventative medicine because it is a non-invasive technique, is safe for both patient and operator, can be performed routinely using medical behaviors, and is also used to follow up on animals undergoing therapy. Ultrasonographic examination is extensively described in bottlenose dolphins (Tursiops spp.),1 but information in killer whales (Orcinus orca) is scarce2. The purpose of this work is to expand the present knowledge of the ultrasonographic appearance of the main abdominal organs of killer whales.
All ultrasound images were collected during routine voluntary training on four apparently healthy killer whales (4 to 19 years old) under professional care, housed at Marineland Park Côte d’Azur, France. Examination were performed in right and left lateral recumbency. Only abdominal organs were described. Ultrasonography was recorded using a Logiq V2, General Electric, with a 2–5 MHz curvilinear transducer. An appropriate preset of the machine was used to obtain evaluable images, excluding “Harmonics”.
The wall of the forestomach was thin with more evident plications than in the dolphin. The content appeared heterogeneous in presence of food, or anechoic in fasted animals. The fundic chamber of killer whales, unlike dolphins, had a wall similar to that of the forestomach but with shorter plications. The content appeared anechoic in fasted animals, or homogeneously echogenic in presence partially digested materials, mixed with microbubbles of gas. The pyloric chamber was elongated with a linear and homogeneous wall. Its content and the one of the duodenal ampulla were always hypoechoic, compared to the fundic chamber content. The echogenicity of the intestinal lumen was usually echoic (food mixed with gas).
The hepatic margins were smooth and sharp. The hepatic parenchyma had a low echogenicity, whereas the vascular structures and the biliary ducts were more echogenic, providing an important contrast of the organ. However, this contrast on the sonograms of liver could have been caused by the presetting used during examination.
The kidneys had a classical plurilobulated architecture, as other cetacean species. The cortex surrounding the medulla of the reniculi could be well distinguished by ultrasound. The diameter of the reniculi and of the ureter at the emergence of the caudal renal pole, were larger compared to the ones of the dolphins. The urinary bladder wall was smooth with anechoic content when filled with urine.
The ultrasonographic examination of the killer whales has overlapping methods to those used in the dolphins, but some differences in the appearance have been highlighted, as for the fundic chamber or the liver. The large size of killer whales also limits the possibility of a complete examination of the entire abdominal cavity.
This study expands the present knowledge of killer whale ultrasonography, providing additional relevant images, which can be used as normal references to be able to recognize and interpret potential anomalies. Further ultrasonographic examinations need to be performed in order to set more specific standard in killer whales.
The authors would like to thank the killer whale trainer team of Marineland Park Côte d’Azur, for their help and support during this study, and for their excellent training skills allowing the realization of the examination on the animals.
1. Saviano P. 2013. Handbook of Ultrasonography in Dolphins. Abdomen, Thorax & Eye. 1st edition. Pietro Saviano Publisher. 188 p.
2. Lacave G. 2015. Development of a Reference Atlas of Killer Whale (Orcinus orca) Ultrasonography. IAAAM 46th Annual Conference Proceedings, Chicago, IL.