Ultrasound at the Zoo

Zoo medicine is quite the paradox. In one way, zoo veterinarians are specialists in that what we do daily; it is very unique and specialized and there are few licensed veterinarians that are employed as full-time clinicians in zoological parks. On the contrary, zoo veterinarians are also the ultimate general practitioners as our patients include everything from invertebrates to great apes and elephants (and all life forms in-between)… and for this wide variety of patients, we attempt to be their pediatrician, surgeon, dermatologist, cardiologist, radiologist, etc. I am fortunate to be the Senior Staff Veterinarian at the Louisville Zoo in Louisville, Kentucky.

In terms of imaging modalities, most zoo hospitals are equipped with plain radiography (film or digital) and have some ultrasound capabilities. A few of the larger zoos in the country have computed tomography (CT) in their on-site hospitals. In Louisville, when one of our patients requires advanced imaging, we make arrangements with local facilities with CT or MRI capabilities.

For ultrasound imaging, we have a portable Sonosite M-Turbo unit with both a curvilinear, 5-2 MHz transducer for primarily transabdominal imaging, and a linear array, 10-5 MHz transducer for primarily transrectal imaging. In addition, we have several donated large rolling Phillips Sonos units with an assortment of probes for both echocardiography and transabdominal imaging. One remains in the Zoo’s Animal Health Center and others are stored and used in animal areas for pregnancy diagnosis, echocardiograms on awake gorillas (through the mesh barrier), or just training/conditioning animals for awake ultrasound exams.

Zoo animals may present unique challenges when ultrasound imaging transcutaneously. In the case of fish and amphibians, imaging through a water bath (without even touching the patient!) can be very effective and noninvasive. The rough scaly skin of some reptiles makes a warm water bath similarly effective as a conductive medium for imaging snakes and lizards. Birds are not often examined via ultrasound because of the extensive respiratory (air sac) system they possess that interferes with the sound waves. For mammals, different species present different challenges. Many mammal species are thickly furred necessitating clipping of hair to establish good contact between the transducer and the skin. For transabdominal imaging, some species are very gassy (hippos, gorillas), which may complicate diagnostic imaging. Large or dangerous mammals that are examined awake via training need to be conditioned to present the body part of interest (chest, abdomen) at the barrier mesh and trust their trainer/keeper to allow contact with the probe. Often the greatest hurdle is habituating the animal to the ultrasound gel! When performing transabdominal imaging in our pregnant African elephant cow, rather than go through gallons of ultrasound gel smeared on her flank to fill in all the cracks and crevices in her thick skin, we run water from a hose just above wherever the transducer is placed.

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As general practitioners, zoo veterinarians have variable amounts of training in ultrasonography. We strive to do the best we can and are constantly learning, but the high variability in our daily tasks makes becoming an expert in ultrasound very difficult. So “it takes a village,” and we will regularly utilize specialists in our community to assist us in providing the best medical care for our patients. If I have a zebra or related species that requires a reproductive ultrasound exam, we will reach out to a local equine veterinarian that can apply their expertise in horses to a related species. Great apes have a high incidence of heart disease so whenever a gorilla or orangutan is anesthetized for an exam, part of the comprehensive care they receive is an echocardiogram by a human sonographer. Female great apes may get attention from our volunteer gynecologic sonographer as part of a reproductive evaluation. If the ultrasound exam is on a sea lion, wolf, or bear, I may contact a veterinary radiologist or veterinary internist competent in ultrasonography to assist.

In summary, ultrasonography represents a valuable, noninvasive, diagnostic tool for the zoo veterinarian.

Have you ever performed an ultrasound examination at a zoo? What was your experience? Comment below, or, AIUM members, continue the conversation on Connect, the AIUM’s online community. 

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Zoli Gyimesi, DVM, is the Senior Veterinarian at the Louisville Zoo in Louisville, Kentucky.

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