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Imaging in Zoological Medicine Practice
Imaging in Zoological Medicine Practice j Michael K. Stoskopf, DVM, PhD, D.ACZM; James Brown, DVM, D.ACVR; and Ryan DeVoe, DVM, D.ACZM, D.ABVP (avian) ABSTRACT: An introduction to zoological radiology, this article presents a brief overview of the variety of imaging modalities and situations faced in the practice of the discipline. These are illustrated by brief case summaries showing the diverse applications of imaging to diagnosis and treatment of wild animals. (J Radiol Nurs 2012;31:81-90.) KEYWORDS: Zoological radiology; Animal imaging.
INTRODUCTION Imagine the need to diagnose a space-occupying lesion in the coelom of a 15-g lungless salamander. Now consider examining a young 4,000-lb elephant for the possibility of a fractured olecranon process the same morning. As you do, you are beginning to appreciate the breadth of challenges faced in the practice day of a zoological medicine specialist, and the importance of diagnostic imaging in providing health care to their diverse patients. Zoological medicine is a discipline that integrates principles of ecology, conservation, and veterinary medicine and applies them to wild animals within natural and artificial environments. To accomplish this mission, zoological medicine practitioners have to take advantage of every possible diagnostic and therapeutic modality, including the knowledge and skills of other specialists. Without a doubt, one of the valuable allies in the challenge can be an intellectually curious veteri-
Michael K. Stoskopf, DVM, PhD, D.ACZM, is a Professor of Wildlife and Aquatic Medicine in the Department of Clinical Sciences, College of Veterinary Medicine, and Biomedical Engineering, College of Engineering, North Carolina State University, Raleigh, NC. James Brown, DVM, D.ACVR, is an Assistant Professor of Radiology, Department of Molecular and Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC. Ryan DeVoe, DVM, D.ACZM, D.ABVP (avian), is a Senior Veterinarian at the NC Zoo, Asheboro, NC, and an Adjunct Assistant Professor of Zoological Medicine, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC. Corresponding author: Michael K. Stoskopf, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606. E-mail: [email protected] 1546-0843/$36.00 Copyright Ó 2012 Michael Stoskopf. Published by Elsevier Inc. on behalf of the Association for Radiologic & Imaging Nursing. All Rights Reserved. doi: 10.1016/j.jradnu.2011.10.006
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nary radiologist if one of those rare individuals is available. For that matter, a skilled narrow species specialist radiologist focused on one taxon of primates, but highly skilled in an imaging modality, might find themselves invited onto a zoological medicine team. A relatively small cadre of dedicated veterinarians specialize in zoological medicine. Through rigorous examination and performance criteria, they serve as diplomates of the American College of Zoological Medicine, the veterinary specialty dedicated to excellence in furthering the health and well being of captive and freeranging wild animals. The responsibilities of many of these veterinarians can focus on free-ranging species of high management or conservation priority, but the largest number of zoological medicine specialists have responsibilities to provide health care for wild animals in captivity. These are sometimes referred to as “zoo vets.” Veterinary radiologists are similarly highly trained and certified by a specialty college, and skilled in the use of the wide range of imaging modalities used in human and veterinary medicine. They are most commonly found in academic settings or in advanced specialty practices and their experience is generally focused on domestic animal species. The first “zoological medicine radiologist” is yet to have evolved, but there can be little doubt that in the not too far future veterinarians will rise to the challenge of becoming double specialty boarded. Until that time, and likely long after it, zoological radiology is a team sport. The nature of the caseload of a zoological medicine practice is defined by the extreme diversity of the population of potential patients. The zoo vet needs to know how to properly handle, anesthetize, and treat their wide range of patients. Radically different skill sets and tools are needed to examine and treat patients that vary from tiny, delicate invertebrates to massive,
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although in some ways equally delicate pachyderms. The taxonomic and size diversity is accompanied by an equally daunting diversity of anatomy and physiology. There are patients that have no limbs, those that have no lungs, and even those that have no stomachs. Even more daunting are all of the little extra bits and parts to be found across the taxonomic spectrum; air sacs, specialized bones, asymmetrical sensory structures, to name just a few. The challenge to know the basic anatomy of all of the species that might be presented is perhaps beyond daunting. Although anatomists over the past centuries have conducted and published anatomic studies and illustrations of many animals, recent synthesis works and collections of smaller studies into general references or texts are relatively rare. In truth, the detailed anatomy of many species is just not known. A veterinary radiologist is an expert in applied comparative anatomy, although their expertise is usually much more highly refined in the realm of domestic species. A zoo vet needs to know where to find what is known, to help serve as a resource for basic anatomic facts for the team. Studies across the taxa (Kaiser, 2008) along with smaller detailed studies (Hahulski, Marcellin-Little, & Stoskopf, 1999; McSweeney & Stoskopf, 1988, 1989a, 1989b) and even texts on avian radiography (Krautwald, 1995; Silverman & Tell, 2009) make finding avian anatomy and radiography techniques relatively straight forward. Perhaps even more so than for the diversity of mammalian patients, although studies ranging from organ topography of sea otters (Stoskopf, Fishman, & Williams, 1990; Stoskopf & Herbert, 1990) to the radiographic anatomy of the elephant foot (Gage, 2006) help supplement more general works (Capello, Lennox, & Widmer, 2008; Krautwald-Junhanns, Pees, Reese, & Tully, 2001; Samour & Naldo, 2007; Silverman & Tell, 2004; Williams, 2004). Unfortunately, the general works are often focused on the same limited number of species. Useful studies are available in primary literature on some amphibians and reptiles (Love, Douglas, Lewbart, & Stoskopf, 1996; Willens et al., 2006), and even some key invertebrates (Berzins et al., 1990; Stoskopf & Oppenheim, 1996), and individual review articles and technique articles are helpful (Blackband & Stoskopf, 1990; Huml, Khoo, Stoskopf, & Forrest, 1993), but it is common for there to be a complete lack of illustrated anatomy or radiographic examples available for a zoological medicine patient. Many anatomic adaptations occur in taxonomically logical patterns. Wings of birds, for example, vary greatly with the type of flight of the bird. These anatomic variations generally follow the functional relationships of birds and bird groups defined in classic ornithology. It is clearly reasonable to expect the wing anatomy of
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a long flighted migratory goose to be more similar to another related migratory goose species than to a flightless ostrich as an extreme example. A basic understanding of natural history and taxonomy can go a long way when no detailed studies are available for a species. Flight habits are only one of many examples of functional impacts on structure that can guide radiographic interpretation across taxonomic lines. Carnivores, whether mammalian, avian, or even Piscean, tend to have much shorter and more simple gastrointestinal tracts than herbivorous species, for example. The clavicular apparati of climbing species are more similar to each other than they are to nonclimbing, rapid running, or swimming species. Modes of locomotion, habits of burrowing or digging, and certainly the sensory modifications related to being active at different parts of the day all have important structural impacts that can be important in interpreting a radiographic case. To be honest, however, at a certain point the basic anatomical works available, and a knowledge of general taxonomic and natural history relationships are not enough to make detailed evaluations of many cases. Then, a number of basic “tricks” help zoological radiology teams make interpretations when working without the complete anatomic knowledge of their species enjoyed by a human radiologist. For situations where only one side of bilaterally symmetrical structures is of concern, the imaging of the contralateral side can provide a valuable control to compare with the affected side. This works well so long as bilateral symmetry is actually normal. This is not always the case. The ear bullae of owls, for example, are dramatically different in size, an adaptation that facilitates the precise localization of sounds when hunting at night. Any attempt to use bilateral symmetry as a guide in interpreting the skull of an owl is thwarted by the major differences in bulla size and their impact on other features. When faced with a very unusual structure or symmetry, a common procedure will be to image another individual of the same species if one is available. Preferably, it should be an animal of the same sex as sexual dimorphism of some structures can be dramatic. Although this increases the risks of the diagnostic effort, it may be a very necessary approach. Some zoological species are simply risky to handle, both for their own safety and that of the handlers. Many zoological species must be maintained under general anesthesia for most imaging modalities and there is always a risk involved in general anesthesia, particularly for those with highly specialized respiratory and cardiovascular systems such as the diving reflexes of marine mammals. It is, of course, possible to infer conclusions based on comparative anatomy from similar, or sometimes even dissimilar, species. Some common basic anatomic
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patterns that can be used to facilitate diagnosis are conserved across many animal taxa including humans. Fortunately, the appearance of organs in any one modality can be surprisingly similar across many species. For example, the sonographic appearance of the liver, spleen, or duodenum in an eagle is almost exactly the same as it is in a timber wolf. Zoological radiology makes use of all available forms of imaging, including some not often considered, such at thermography. Advances in technology, particularly in ultrasound and digital plain film radiography are revolutionizing imaging options in larger zoological institutions. Plain film radiography remains the backbone of zoological radiology. Some of the larger zoological institutions have been able to invest in digital radiography equipment and as more advanced generations of equipment are placed in service, smaller zoological institutions are benefiting from donations of older technology. Some smaller zoos still work with film processors and even dip tanks, but plain film techniques in zoological practice are used for a wide range of diagnoses. The portability and safety of ultrasound as newer lighter and more capable units become available is pushing this modality to compete heavily with plain film radiography as the first modality of choice. Advances in academic radiology departments are greatly improving the options available to zoological species, making computed tomography (CT) and magnetic resonance imaging (MRI) more available, and more sophisticated techniques. Some patients require more creativity to obtain useful images, but the basic principle of obtaining multiple standardized views is important across the range of zoological patients, even when they are fish. The following cases are chosen to illustrate the diversity and challenges of zoological radiology, and how different modalities play an important role in diagnosis and treatment.
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the gastrointestinal tract. Gas pressures in the swim bladder are regulated through a physiological coordination of a gas gland that strips oxygen from hemoglobin using the Root effect, and a gas-resorbing organ often called the oval window. The complex physiology involved in maintaining proper buoyancy for a fish can be perturbed by many things, including infections and trauma. Although for some longer duration imaging techniques fish will be anesthetized and positioned in tubs of water, for most plain film studies it is reasonable to set up the radiography equipment and then anesthetize the fish and position it quickly out of water on plastic bags (Figure 1). A horizontal beam is particularly useful for obtaining good quality ventral-dorsal views. The lateral and ventral-dorsal views of the Koi presented with buoyancy problems are shown in Figure 2 along with a lateral view of a normal similarly sized Koi. At first glance, the patient seems not to have a swim bladder at all. More careful examination shows two structures with mottled appearance in the same areas where we would expect the two chambers of the swim bladder. The walls of these structures appear to be thickened. A key differential diagnosis after seeing these radiographs is severe bacterial or fungal infection of the swim bladder. The follow-up diagnostic procedure of choice would be an ultrasound-guided aspirate biopsy for cytology and culture and sensitivity testing. A severe case such as this one may not respond to systemic antimicrobial therapy. There is a significant chance that the oval and the gas gland have been damaged by the inflammatory process. Exploratory surgery, debridement, and even excision of the infected swim bladder may be necessary to save the patient’s life. Case: pregnant chimpanzee Ultrasound is rapidly becoming one of the most used tools in zoological imaging, encroaching on the title
Case: Koi with buoyancy problems A large Koi was noticed to be spending all of its time at the bottom of its pond, and exerting a great deal of effort to rise in the water column. Koi, large, colorful domestic carp have been bred for centuries for conformation and color patterns and are often very valuable to Koi enthusiasts. When these long-lived animals experience health problems, their owners will most commonly seek out a zoological medicine practitioner. With these presenting signs, the first diagnostic order will usually be for a series of plain film radiographs to evaluate the condition of the swim bladder, a gas-filled structure derived embryologically from the gastrointestinal tract that among other things is used by many fish species to regulate their buoyancy. Koi have double-chambered physoclistous swim bladders that in adult fish are isolated from VOLUME 31 ISSUE 3
Figure 1. An anesthetized Koi is positioned for a dorsoventral radiograph using a horizontal beam. The equipment is set up before positioning the fish to minimize the impact of having the patient out of the water (photo courtesy of G. Lewbart).
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Figure 2. Radiographs of a Koi presented for spending nearly all of its time on the bottom, and struggling to swim to the surface to feed. There is increased soft-tissue opacity throughout the swim bladder, such that only small, faint gas bubbles are visible and the wall appears thick. The lateral radiograph in the lower left corner is of a different animal with no abnormal swimming patterns.
that still is held by plain film radiography. The portability and capabilities of the newest ultrasound units make them ideal for use in exhibit areas, often eliminating the need to transport cases to the hospital for diagnostics. Also, as zoological medicine specialists become more skilled in the use of ultrasound, many routine assessments are being done by the clinicians themselves. Of course, the more complex cases are still best examined by skilled ultrasonographers. Managing reproduction in a chimpanzee troop has several key challenges including diagnosis of the pregnancy and careful prediction of birthing time to facilitate observations to ensure the newborn infant is not mishandled by the mother. This later issue is particularly a concern for a primagravida female because of the higher risks of pregnancy failure and inappropriate behavior after birth. Maki, a 16-year-old female chimpanzee in troop of 13 animals at the North Carolina zoo was taken off of birth control in 2009 and introduced to an appropriate male. She failed to cycle normally in January 2010 and was diagnosed as pregnant on the basis of a commercial over the counter urine pregnancy test. The pregnancy was confirmed in February by ultrasound examination. To accomplish this, Maki was trained to come to the mesh barrier of her inside enclosure and to grab two polyvinylchloride pipe handles placed above her head and lean her lower abdomen into a metal port in the steel mesh wall (Figure 3). The hair of a chimpanzee presents greater problems in establishing contact with the ultrasound probe than is the case in most humans, and the challenge is exacerbated because chimpanzees do not care much for ultrasound 84
gel, and regularly will break training and run from their examination station to try and groom away the gel. Shaving the abdomen presents other problems. Maki was not in favor of the idea, and generally if shaving can be avoided the animals make a better exhibit. Rather than gel, water was used for the contact medium between the probe and Maki’s skin. Throughout the examination, Maki’s keeper/trainer would provide juice and other treats to keep the animal focused on maintaining
Figure 3. Maki, an adult female chimpanzee receives a sweet juice reward for grabbing the polyvinylchloride pipe positioning handles to allow Dr. Betsy Stringer to conduct a safe pregnancy ultrasound examination with the assistance of hospital keeper Gisela Wiggins holding the portable unit and Beth McChesney, one of Maki’s keepers who helped to train the behavior (photo courtesy of North Carolina Zoological Park). Color illustration online.
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her position. Nevertheless, the ultrasonographer manipulating the probe has to stay constantly vigilant to avoid being grabbed or losing the probe to the chimpanzee. Maki is a very well-behaved chimpanzee but these very intelligent animals will wait patiently for an opportunity to steal an interesting item, moving very quickly and with amazing dexterity. Maki was examined by ultrasound monthly throughout her 242-day gestation period. Viability of the fetus was easily ascertained, but limitations of the examination technique made accurate observation of biparietal diameters very difficult. In the last few weeks of her pregnancy, Maki was scanned frequently looking for positioning signs that might portend eminent parturition and signal the need for the 24-hr birthing watch. In early August 2010, Maki had an uncomplicated delivery of a healthy female baby, Nori. Unfortunately, despite heroic attempts to supplement Maki’s lack of care for her first-born infant, Nori had to be removed for hand rearing at 5 days of age. Innovative adaptations of the hand-rearing process allowed her to be successfully reintroduced to adult chimpanzees after about 4 months (Webb & Ireland, 2010) and she is doing very well.
Figure 4. Alice White Rhino rests, taking a load off of her sore front feet (photo courtesy of E. Stringer). VOLUME 31 ISSUE 3
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Figure 5. Thermographic image of the front legs of Alice, the white rhinoceros, showing marked inflammation in the right foot (image courtesy of Christie McCoy-Nichols, Thermal Discovery LLC). Color illustration online.
Case: sore-footed rhinoceros Older animals in captivity often experience degenerative joint disease that can be very challenging to treat. Large species are particularly vulnerable to physical process that can force foreign materials across their plantar barriers and as a result podiatry is a complex part of zoological practices. The portability of modern thermography cameras makes thermal imaging a valuable tool in the assessment of many conditions, including the challenge of diagnosing and monitoring the therapeutic progress of foot abscesses and arthritis. Alice, a superannuated female white rhinoceros is a good example of the challenges of managing large geriatric patients. The risk of anesthesia is generally higher in the large species and certainly higher in older animals. It is particularly important in these cases that the preanesthesia evaluation of the patient’s condition be as thorough as possible to plan and focus the procedures done during the anesthesia. Alice is plagued by general osteoarthritis complicated by frequent foot abscesses that require careful monitoring after debridement. The use of video thermography allows veterinarians to localize abscesses and monitor the effects of therapy on the inflammatory processes (Figures 4 and 5). Frequently, developing abscesses are detected using thermography long before external signs are apparent, allowing for early intervention. Alice’s feet are also radiographed frequently to assess her osteomyelitis using a portable X-ray machine and a heavyduty acrylic sleeve constructed to protect the X-ray plate when bearing the full weight of the rhinoceros. Alice is coaxed to stand in position on the acrylic sleeve using a combination of food and tactile rewards. White rhinoceroses are not particularly food motivated, but they love to be scratched and rubbed.
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Case: sea turtle head trauma Zoological imaging is not limited to the medical management of captive wildlife. Important conservation species such as the endangered sea turtles also benefit from diagnostic imaging. Trauma, often inflicted by unfortunate encounters with boats and propellers is one of the most common reasons a sea turtle might find itself on an imaging gantry. A84456 is a loggerhead sea turtle that stranded on the North Carolina coast and was fortunate enough to be taken to a sea turtle rescue hospital for stabilization. Although the severe trauma to the skull was certainly evident without the aid of imaging, careful 3D reconstructions of CT images (Figure 6) allowed surgeons to assess the turtle’s prognosis and then to plan a successful repair of the trauma. A raised bridging system of plastic plates successfully stabilized the skull and after a year long recovery, rerelease into the wild is in this turtle’s future. Case: lemur with a swollen face Zoological species can have very unusual anatomy, which in turn can make it important to be very conservative in interpreting diagnostic images. Poe, a wild caught male Aye Aye is a case in point. One of very few Aye Ayes ever held in captivity, Poe is an important part of the conservation research efforts of the famous Duke University Lemur Center. Captured in the wild in 1987 when he was estimated to be a year old, Poe is at least Figure 7. Poe, an adult male Aye Aye at the Duke Lemur Center. Note the unusual forefinger and large ears used in detecting grubs burrowing in trees (photo courtesy of David Haring, Duke Lemur Center).
Figure 6. A 3D reconstruction of a computed tomography examination of loggerhead sea turtle A84456, which stranded on the North Carolina coast after being hit by a boat propeller. Reconstructive surgery and over a year of recovery and rehabilitation repaired the defects. Color illustration online. 86
23 years old and perhaps older. A medium-sized prosimian of dramatic appearance (Figure 7), Poe has very large ears, a highly modified jaw, and tooth structure, and a very unusual extremely elongated third digit with a 360-degree range of motion facilitate a life style of detecting, capturing, and feeding on insects boring deep in wood. When Poe was presented to the Lemur Center veterinarians for a swollen face, a diagnosis of a retrobulbar abscess was made, potentially because of dental problems. However, despite appropriate culture and sensitivity testing, antibiotic treatment, and a tooth extraction, the problem did not resolve completely. An exploratory surgery to follow a fistulous tract in the mandible was performed to rule out the presence of a foreign body or sequestrum. None were found. Extensive postsurgical treatments did not resolve the infection, and the challenging nature of the case led to an MRI study of Poe’s head (Figure 8). On T2-weighted images, regional hyperintensity in the soft tissue adjacent to the left ramus
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Figure 8. Magnetic resonance imaging of Poe the Aye Aye: T1, T2, and T1 C gadolinium contrast-medium images. Transverse plane images are analogous to the coronal view and dorsal plane images are analogous to axial view in humans. On the T2 image, there is regional hyperintensity in the soft tissue adjacent to the left ramus of the mandible that is most severe laterally. The left masseter and pterygoid muscles are enlarged. With contrast medium, there is intense, regional enhancement surrounding the left ramus of the mandible medially and laterally, extending dorsally toward the condylar process. Dorsal plane images depict the rostrocaudal extent of this lesion.
of Poe’s mandible that was most severe laterally was noted, indicating edema and inflammation. The left masseter and pterygoid muscles were enlarged. After administration of gadolinium contrast medium, there was intense, regional enhancement surrounding the left ramus of the mandible medially and laterally, extending dorsally toward the condylar process suggesting osteomyelitis of Poe’s left temporomandibular joint. Aggressive antibiotic therapy using Azithromycin seemed to resolve the condition for some time, but over the next 4 years facial swelling has recurred several times, affecting both sides of Poe’s face. Extensive culture-guided antibiotic therapy including the use of embedded antibiotic laden pleuronic gel and surgical interventions including dental modifications guided by plain film radiography have only temporarily halted the condition. During the process of managing Poe’s case, we have learned that the unusual continuously growing incisors of the Aye Aye stop growing late in life. How this may relate to Poe’s condition is unknown, VOLUME 31 ISSUE 3
but Poe’s veterinarians continue to treat flares of the condition as they arise and work to provide Poe with a good quality of life, while seeking the underlying cause of the condition. Case: gorilla radiotherapy Captive wildlife tend to live much longer than they would in the wild and as a result many zoos manage what would be considered to be geriatric collections. As a result, cancer is a common problem that must be dealt with by zoological clinicians. This is particularly true for mammals, and one informal survey in a major zoo found some form of cancer present in nearly half of all mammals that were necropsied over a series of years. Veterinary oncologists have researched and developed therapeutic approaches to many types of cancer over the years and both curative and palliative therapies, including radiation therapy will be applied to zoological species when a reasonable plan that balances the
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Figure 9. Katie, the gorilla being positioned on the gantry before imaging to guide design of her radiation therapy (photo courtesy of E. Stringer).
challenges of managing the animal for treatment and concerns about quality of life can be achieved. Katie, a 36-year-old female western lowland gorilla was examined by veterinarians at the North Carolina Zoological Park for intermittent vaginal bleeding (Stringer et al., 2010). Plain film radiographs were not informative, but vaginoscopy revealed a thickened vaginal mucosa and biopsies were diagnosed and differentiated squamous cell carcinoma. Abdominal ultrasound showed a heteroechoic mass 7 cm in diameter in the area of the uterus, and thoracic radiographs showed no evidence of metastasis. CT of the abdomen, pelvis, and thorax was performed with the patient supine in a Vacloc positioning device to facilitate repeatable positioning (Figure 9). Both pre- and postcontrast series were obtained. CT could not distinguish the ovaries and revealed the locally invasive mass involved in the uterine body and horns and extended caudally through the cervix and into the vagina (Figure 10). There were no signs of metastasis and a decision was made to
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proceed with palliative radiation treatment using CT-based computerized treatment planning software (Figure 11). Katie was managed in a large custom gorilla squeeze cage and anesthetized for each treatment. A total dose of 16 Gy was delivered in four fractions of 4 Gy given two per day 6 hr apart, for two consecutive days. After treatment, Katie had decreased appetite and lethargy for approximately 2 weeks but recovered well. Reevaluation of the tumor by CT examination 8 weeks later indicated a modest response to therapy and the continued lack of evidence of metastasis. The decision was made to administer a second round of palliative radiation therapy to Katie. She tolerated this round better than the first, with no signs of inappetence or lethargy. Katie was then allowed to live her life in her naturalistic exhibit at the NC Zoological Park, being monitored daily for quality of life. After several months, Katie’s condition began to deteriorate and she was humanely euthanized. DISCUSSION Zoological radiologists use any available imaging technique to facilitate the diagnosis and treatment of their very special patients. The nature of the patients poses some interesting challenges, both logistically and in obtaining and interpreting the images. Special views that would not be routine in human radiology help compensate for anatomic differences. A good example is the routine use of anterior-posterior views for examination of turtles, particularly those suspected to have pulmonary lesions. This view, which would be singularly unproductive in human radiology obtains a clear view of the lungs of turtles without interference of other organs. The lungs of turtles are dorsal to all of the underlying viscera, making an anterior to posterior
Figure 10. Katie, the gorilla’s computed tomography images: transverse and dorsal images with iodinated contrast medium. A spherical, multilobed, and cavitary mass extends to the right from the remnant of the uterine corpus, which is invaded by the tumor near the cervix. 88
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with very different expertise and experience. As the available equipment and modalities continue to evolve and become available to zoological institutions, the management of the health of wildlife of all types is greatly enhanced.
References
Figure 11. Katie, the gorilla being positioned for radiation therapy (photo courtesy of E. Stringer).
orientation of the beam particularly useful for showing lung fields. In some cases, unusual measures are used to simulate standard human positioning. An example would be for thoracic imaging of primates. Because nonhuman primates have to be anesthetized for radiography, it would be natural to position them in recumbent positions used for other animals. However, these positions result in organ relationships that are quite different from those obtained in standing positions used routinely to obtain human chest films. The similarity of primate anatomy to human anatomy, and the often much greater experience of human radiologists reading chest films have made it common practice to consult with human radiologists on reading these cases. To optimize the ability of human radiologists to interpret nonhuman primate films, it is routine for zoological radiologists to literally hang anesthetized primate patients from their arms to try and simulate the standard standing films taken of humans. This works reasonably well for small- and even medium-sized primates, but not for the large apes. The size of patients can present challenges. Large adult gorillas challenge the weight limits of normal imaging gantries, and bore diameters of some advanced imaging techniques can only accommodate extremities of some zoological patients, even when special heavyduty gantries are available. For very small patients, the challenge is in providing images with adequate resolution to allow their enlargement for careful assessment. Digital imaging equipment has gone a long way to solve the problem of enlargement of images of very small patients that otherwise could only be adequately imaged with special equipment with very narrow tube focal apertures. With all of the challenges, zoological radiology is an intellectually stimulating field that is very definitely a team sport, requiring the collaboration of individuals VOLUME 31 ISSUE 3
Berzins, I.K., Maslanka, P., Montali, R.J., Davis, K.J., Pletcher, J.M., & Stoskopf, M.K. (1990). Anatomy and histology of the common cuttlefish, Sepia officinalis. Washington, DC: Armed Forces Institute of Pathology Study Set. Blackband, S.J., & Stoskopf, M.K. (1990). In vivo nuclear magnetic resonance imaging and spectroscopy of aquatic organisms. Magnetic Resonance Imaging, 8(2), 191-198. Capello, V., Lennox, A.M., & Widmer, W. (2008). Clinical radiology of exotic companion mammals. Wiley-Blackwell. Gage, L. (2006). Radiology. Fowler, M., Makota, S. The biology, medicine and surgery of elephants: Blackwell Publishing, pp. 192-198. Hahulski, G., Marcellin-Little, D.J., & Stoskopf, M.K. (1999). Morphologic evaluation of rotated tibiotarsal bones in immature ostriches (Struthio camelus). Journal of Avian Medicine and Surgery, 13(4), 252-260. Huml, R.A., Khoo, L.H., Stoskopf, M.K., & Forrest, L.J. (1993). Radiographic diagnosis. Veterinary Radiology and Ultrasound, 34(3), 178-180. Kaiser, G.W. (2008). The inner bird: Anatomy and evolution. University of Washington Press. Krautwald, M. (1995). Atlas of radiographic anatomy and diagnosis of cage birds. Blackwell. Krautwald-Junhanns, M., Pees, M., Reese, S., & Tully, T. (2001). Diagnostic imaging of exotic pets: Birds, small mammals, reptiles. Schluetersche. Love, N.E., Douglas, J.P., Lewbart, G.A., & Stoskopf, M.K. (1996). Radiographic and ultrasonographic evaluation of egg retention and peritonitis in two green iquanas, Iquana iguana. Journal of Veterinary Radiology and Ultrasound, 37(1), 68-73. McSweeney, T., & Stoskopf, M.K. (1988). Selected anatomical features of the neck and gular sac of the brown pelican (Pelecanus occidentalis). Journal of Zoo and Wildlife Medicine, 19, 116-121. McSweeney, T., & Stoskopf, M.K. (1989a). Limb anatomy of the brown pelican (Pelecanus occidentalis). Journal of Zoo and Wildlife Medicine, 20(2), 191-198. McSweeney, T., & Stoskopf, M.K. (1989b). Selected features of the abdominal and thoracic anatomy of the brown pelican (Pelecanus occidentalis). Journal of Zoo and Wildlife Medicine, 20(2), 184-190. Samour, J., & Naldo, J.L. (2007). Veterinary diagnostic imaging: Birds, exotic pets and wildlife. Saunders Ltd. Silverman, S., & Tell, L. (2004). Radiology of rodents, rabbits and ferrets: An atlas of normal anatomy and positioning. Philadelphia, PA: W.B. Saunders. Silverman, S., & Tell, L. (2009). Radiology of birds: An atlas of normal anatomy and positioning. Saunders. Stoskopf, M.K., Fishman, E., & Williams, T. (1990). Volumetric imaging for three-dimensional display of the skeletal anatomy of the sea otter. Veterinary Radiology, 31(3), 142-145. Stoskopf, M.K., & Herbert, D. (1990). Selected anatomical features of the sea otter (Enhydra lutris). Journal of Zoo and Wildlife Medicine, 21(1), 36-47.
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Stoskopf, M.K., & Oppenheim, B.S. (1996). Anatomical features of Octopus bimaculoides and Octopus digueti. Journal of Zoo and Wildlife Medicine, 27(1), 1-18. Stringer, E.M., DeVoe, R.S., Valea, F., Toma, S., Mulvaney, G., & Pruitt, A., et al. (2010). Medical and surgical management of reproductive neoplasia in two western lowland gorillas (Gorilla gorilla gorilla). Journal of Medical Primatology, 39, 328-335. Webb, T. & Ireland, J. (2010). Dietary practices for hand-rearing of infant chimpanzee (Pan troglodytes) at the North Carolina
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zoo (abstract). Sixth Crissey Zoological Nutrition Symposium, Raleigh, NC; pp. 27. Willens, S., Dupree, S.H., Stoskopf, M.K., Lewbart, G.A., Taylor, S.K., & Kennedy-Stoskopf, S. (2006). Measurements of common iliac arterial blood flow in anurans using doppler ultrasound. Journal of Zoo and Wildlife Medicine, 37(2), 97-101. Williams, J. (2004). Diagnostic imaging of avian and exotic animals. Iowa State Press.
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INTRODUCTION Imagine the need to diagnose a space-occupying lesion in the coelom of a 15-g lungless salamander. Now consider examining a young 4,000-lb elephant for the possibility of a fractured olecranon process the same morning. As you do, you are beginning to appreciate the breadth of challenges faced in the practice day of a zoological medicine specialist, and the importance of diagnostic imaging in providing health care to their diverse patients. Zoological medicine is a discipline that integrates principles of ecology, conservation, and veterinary medicine and applies them to wild animals within natural and artificial environments. To accomplish this mission, zoological medicine practitioners have to take advantage of every possible diagnostic and therapeutic modality, including the knowledge and skills of other specialists. Without a doubt, one of the valuable allies in the challenge can be an intellectually curious veteri-
Michael K. Stoskopf, DVM, PhD, D.ACZM, is a Professor of Wildlife and Aquatic Medicine in the Department of Clinical Sciences, College of Veterinary Medicine, and Biomedical Engineering, College of Engineering, North Carolina State University, Raleigh, NC. James Brown, DVM, D.ACVR, is an Assistant Professor of Radiology, Department of Molecular and Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC. Ryan DeVoe, DVM, D.ACZM, D.ABVP (avian), is a Senior Veterinarian at the NC Zoo, Asheboro, NC, and an Adjunct Assistant Professor of Zoological Medicine, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC. Corresponding author: Michael K. Stoskopf, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606. E-mail: [email protected] 1546-0843/$36.00 Copyright Ó 2012 Michael Stoskopf. Published by Elsevier Inc. on behalf of the Association for Radiologic & Imaging Nursing. All Rights Reserved. doi: 10.1016/j.jradnu.2011.10.006
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nary radiologist if one of those rare individuals is available. For that matter, a skilled narrow species specialist radiologist focused on one taxon of primates, but highly skilled in an imaging modality, might find themselves invited onto a zoological medicine team. A relatively small cadre of dedicated veterinarians specialize in zoological medicine. Through rigorous examination and performance criteria, they serve as diplomates of the American College of Zoological Medicine, the veterinary specialty dedicated to excellence in furthering the health and well being of captive and freeranging wild animals. The responsibilities of many of these veterinarians can focus on free-ranging species of high management or conservation priority, but the largest number of zoological medicine specialists have responsibilities to provide health care for wild animals in captivity. These are sometimes referred to as “zoo vets.” Veterinary radiologists are similarly highly trained and certified by a specialty college, and skilled in the use of the wide range of imaging modalities used in human and veterinary medicine. They are most commonly found in academic settings or in advanced specialty practices and their experience is generally focused on domestic animal species. The first “zoological medicine radiologist” is yet to have evolved, but there can be little doubt that in the not too far future veterinarians will rise to the challenge of becoming double specialty boarded. Until that time, and likely long after it, zoological radiology is a team sport. The nature of the caseload of a zoological medicine practice is defined by the extreme diversity of the population of potential patients. The zoo vet needs to know how to properly handle, anesthetize, and treat their wide range of patients. Radically different skill sets and tools are needed to examine and treat patients that vary from tiny, delicate invertebrates to massive,
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although in some ways equally delicate pachyderms. The taxonomic and size diversity is accompanied by an equally daunting diversity of anatomy and physiology. There are patients that have no limbs, those that have no lungs, and even those that have no stomachs. Even more daunting are all of the little extra bits and parts to be found across the taxonomic spectrum; air sacs, specialized bones, asymmetrical sensory structures, to name just a few. The challenge to know the basic anatomy of all of the species that might be presented is perhaps beyond daunting. Although anatomists over the past centuries have conducted and published anatomic studies and illustrations of many animals, recent synthesis works and collections of smaller studies into general references or texts are relatively rare. In truth, the detailed anatomy of many species is just not known. A veterinary radiologist is an expert in applied comparative anatomy, although their expertise is usually much more highly refined in the realm of domestic species. A zoo vet needs to know where to find what is known, to help serve as a resource for basic anatomic facts for the team. Studies across the taxa (Kaiser, 2008) along with smaller detailed studies (Hahulski, Marcellin-Little, & Stoskopf, 1999; McSweeney & Stoskopf, 1988, 1989a, 1989b) and even texts on avian radiography (Krautwald, 1995; Silverman & Tell, 2009) make finding avian anatomy and radiography techniques relatively straight forward. Perhaps even more so than for the diversity of mammalian patients, although studies ranging from organ topography of sea otters (Stoskopf, Fishman, & Williams, 1990; Stoskopf & Herbert, 1990) to the radiographic anatomy of the elephant foot (Gage, 2006) help supplement more general works (Capello, Lennox, & Widmer, 2008; Krautwald-Junhanns, Pees, Reese, & Tully, 2001; Samour & Naldo, 2007; Silverman & Tell, 2004; Williams, 2004). Unfortunately, the general works are often focused on the same limited number of species. Useful studies are available in primary literature on some amphibians and reptiles (Love, Douglas, Lewbart, & Stoskopf, 1996; Willens et al., 2006), and even some key invertebrates (Berzins et al., 1990; Stoskopf & Oppenheim, 1996), and individual review articles and technique articles are helpful (Blackband & Stoskopf, 1990; Huml, Khoo, Stoskopf, & Forrest, 1993), but it is common for there to be a complete lack of illustrated anatomy or radiographic examples available for a zoological medicine patient. Many anatomic adaptations occur in taxonomically logical patterns. Wings of birds, for example, vary greatly with the type of flight of the bird. These anatomic variations generally follow the functional relationships of birds and bird groups defined in classic ornithology. It is clearly reasonable to expect the wing anatomy of
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a long flighted migratory goose to be more similar to another related migratory goose species than to a flightless ostrich as an extreme example. A basic understanding of natural history and taxonomy can go a long way when no detailed studies are available for a species. Flight habits are only one of many examples of functional impacts on structure that can guide radiographic interpretation across taxonomic lines. Carnivores, whether mammalian, avian, or even Piscean, tend to have much shorter and more simple gastrointestinal tracts than herbivorous species, for example. The clavicular apparati of climbing species are more similar to each other than they are to nonclimbing, rapid running, or swimming species. Modes of locomotion, habits of burrowing or digging, and certainly the sensory modifications related to being active at different parts of the day all have important structural impacts that can be important in interpreting a radiographic case. To be honest, however, at a certain point the basic anatomical works available, and a knowledge of general taxonomic and natural history relationships are not enough to make detailed evaluations of many cases. Then, a number of basic “tricks” help zoological radiology teams make interpretations when working without the complete anatomic knowledge of their species enjoyed by a human radiologist. For situations where only one side of bilaterally symmetrical structures is of concern, the imaging of the contralateral side can provide a valuable control to compare with the affected side. This works well so long as bilateral symmetry is actually normal. This is not always the case. The ear bullae of owls, for example, are dramatically different in size, an adaptation that facilitates the precise localization of sounds when hunting at night. Any attempt to use bilateral symmetry as a guide in interpreting the skull of an owl is thwarted by the major differences in bulla size and their impact on other features. When faced with a very unusual structure or symmetry, a common procedure will be to image another individual of the same species if one is available. Preferably, it should be an animal of the same sex as sexual dimorphism of some structures can be dramatic. Although this increases the risks of the diagnostic effort, it may be a very necessary approach. Some zoological species are simply risky to handle, both for their own safety and that of the handlers. Many zoological species must be maintained under general anesthesia for most imaging modalities and there is always a risk involved in general anesthesia, particularly for those with highly specialized respiratory and cardiovascular systems such as the diving reflexes of marine mammals. It is, of course, possible to infer conclusions based on comparative anatomy from similar, or sometimes even dissimilar, species. Some common basic anatomic
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patterns that can be used to facilitate diagnosis are conserved across many animal taxa including humans. Fortunately, the appearance of organs in any one modality can be surprisingly similar across many species. For example, the sonographic appearance of the liver, spleen, or duodenum in an eagle is almost exactly the same as it is in a timber wolf. Zoological radiology makes use of all available forms of imaging, including some not often considered, such at thermography. Advances in technology, particularly in ultrasound and digital plain film radiography are revolutionizing imaging options in larger zoological institutions. Plain film radiography remains the backbone of zoological radiology. Some of the larger zoological institutions have been able to invest in digital radiography equipment and as more advanced generations of equipment are placed in service, smaller zoological institutions are benefiting from donations of older technology. Some smaller zoos still work with film processors and even dip tanks, but plain film techniques in zoological practice are used for a wide range of diagnoses. The portability and safety of ultrasound as newer lighter and more capable units become available is pushing this modality to compete heavily with plain film radiography as the first modality of choice. Advances in academic radiology departments are greatly improving the options available to zoological species, making computed tomography (CT) and magnetic resonance imaging (MRI) more available, and more sophisticated techniques. Some patients require more creativity to obtain useful images, but the basic principle of obtaining multiple standardized views is important across the range of zoological patients, even when they are fish. The following cases are chosen to illustrate the diversity and challenges of zoological radiology, and how different modalities play an important role in diagnosis and treatment.
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the gastrointestinal tract. Gas pressures in the swim bladder are regulated through a physiological coordination of a gas gland that strips oxygen from hemoglobin using the Root effect, and a gas-resorbing organ often called the oval window. The complex physiology involved in maintaining proper buoyancy for a fish can be perturbed by many things, including infections and trauma. Although for some longer duration imaging techniques fish will be anesthetized and positioned in tubs of water, for most plain film studies it is reasonable to set up the radiography equipment and then anesthetize the fish and position it quickly out of water on plastic bags (Figure 1). A horizontal beam is particularly useful for obtaining good quality ventral-dorsal views. The lateral and ventral-dorsal views of the Koi presented with buoyancy problems are shown in Figure 2 along with a lateral view of a normal similarly sized Koi. At first glance, the patient seems not to have a swim bladder at all. More careful examination shows two structures with mottled appearance in the same areas where we would expect the two chambers of the swim bladder. The walls of these structures appear to be thickened. A key differential diagnosis after seeing these radiographs is severe bacterial or fungal infection of the swim bladder. The follow-up diagnostic procedure of choice would be an ultrasound-guided aspirate biopsy for cytology and culture and sensitivity testing. A severe case such as this one may not respond to systemic antimicrobial therapy. There is a significant chance that the oval and the gas gland have been damaged by the inflammatory process. Exploratory surgery, debridement, and even excision of the infected swim bladder may be necessary to save the patient’s life. Case: pregnant chimpanzee Ultrasound is rapidly becoming one of the most used tools in zoological imaging, encroaching on the title
Case: Koi with buoyancy problems A large Koi was noticed to be spending all of its time at the bottom of its pond, and exerting a great deal of effort to rise in the water column. Koi, large, colorful domestic carp have been bred for centuries for conformation and color patterns and are often very valuable to Koi enthusiasts. When these long-lived animals experience health problems, their owners will most commonly seek out a zoological medicine practitioner. With these presenting signs, the first diagnostic order will usually be for a series of plain film radiographs to evaluate the condition of the swim bladder, a gas-filled structure derived embryologically from the gastrointestinal tract that among other things is used by many fish species to regulate their buoyancy. Koi have double-chambered physoclistous swim bladders that in adult fish are isolated from VOLUME 31 ISSUE 3
Figure 1. An anesthetized Koi is positioned for a dorsoventral radiograph using a horizontal beam. The equipment is set up before positioning the fish to minimize the impact of having the patient out of the water (photo courtesy of G. Lewbart).
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Figure 2. Radiographs of a Koi presented for spending nearly all of its time on the bottom, and struggling to swim to the surface to feed. There is increased soft-tissue opacity throughout the swim bladder, such that only small, faint gas bubbles are visible and the wall appears thick. The lateral radiograph in the lower left corner is of a different animal with no abnormal swimming patterns.
that still is held by plain film radiography. The portability and capabilities of the newest ultrasound units make them ideal for use in exhibit areas, often eliminating the need to transport cases to the hospital for diagnostics. Also, as zoological medicine specialists become more skilled in the use of ultrasound, many routine assessments are being done by the clinicians themselves. Of course, the more complex cases are still best examined by skilled ultrasonographers. Managing reproduction in a chimpanzee troop has several key challenges including diagnosis of the pregnancy and careful prediction of birthing time to facilitate observations to ensure the newborn infant is not mishandled by the mother. This later issue is particularly a concern for a primagravida female because of the higher risks of pregnancy failure and inappropriate behavior after birth. Maki, a 16-year-old female chimpanzee in troop of 13 animals at the North Carolina zoo was taken off of birth control in 2009 and introduced to an appropriate male. She failed to cycle normally in January 2010 and was diagnosed as pregnant on the basis of a commercial over the counter urine pregnancy test. The pregnancy was confirmed in February by ultrasound examination. To accomplish this, Maki was trained to come to the mesh barrier of her inside enclosure and to grab two polyvinylchloride pipe handles placed above her head and lean her lower abdomen into a metal port in the steel mesh wall (Figure 3). The hair of a chimpanzee presents greater problems in establishing contact with the ultrasound probe than is the case in most humans, and the challenge is exacerbated because chimpanzees do not care much for ultrasound 84
gel, and regularly will break training and run from their examination station to try and groom away the gel. Shaving the abdomen presents other problems. Maki was not in favor of the idea, and generally if shaving can be avoided the animals make a better exhibit. Rather than gel, water was used for the contact medium between the probe and Maki’s skin. Throughout the examination, Maki’s keeper/trainer would provide juice and other treats to keep the animal focused on maintaining
Figure 3. Maki, an adult female chimpanzee receives a sweet juice reward for grabbing the polyvinylchloride pipe positioning handles to allow Dr. Betsy Stringer to conduct a safe pregnancy ultrasound examination with the assistance of hospital keeper Gisela Wiggins holding the portable unit and Beth McChesney, one of Maki’s keepers who helped to train the behavior (photo courtesy of North Carolina Zoological Park). Color illustration online.
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her position. Nevertheless, the ultrasonographer manipulating the probe has to stay constantly vigilant to avoid being grabbed or losing the probe to the chimpanzee. Maki is a very well-behaved chimpanzee but these very intelligent animals will wait patiently for an opportunity to steal an interesting item, moving very quickly and with amazing dexterity. Maki was examined by ultrasound monthly throughout her 242-day gestation period. Viability of the fetus was easily ascertained, but limitations of the examination technique made accurate observation of biparietal diameters very difficult. In the last few weeks of her pregnancy, Maki was scanned frequently looking for positioning signs that might portend eminent parturition and signal the need for the 24-hr birthing watch. In early August 2010, Maki had an uncomplicated delivery of a healthy female baby, Nori. Unfortunately, despite heroic attempts to supplement Maki’s lack of care for her first-born infant, Nori had to be removed for hand rearing at 5 days of age. Innovative adaptations of the hand-rearing process allowed her to be successfully reintroduced to adult chimpanzees after about 4 months (Webb & Ireland, 2010) and she is doing very well.
Figure 4. Alice White Rhino rests, taking a load off of her sore front feet (photo courtesy of E. Stringer). VOLUME 31 ISSUE 3
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Figure 5. Thermographic image of the front legs of Alice, the white rhinoceros, showing marked inflammation in the right foot (image courtesy of Christie McCoy-Nichols, Thermal Discovery LLC). Color illustration online.
Case: sore-footed rhinoceros Older animals in captivity often experience degenerative joint disease that can be very challenging to treat. Large species are particularly vulnerable to physical process that can force foreign materials across their plantar barriers and as a result podiatry is a complex part of zoological practices. The portability of modern thermography cameras makes thermal imaging a valuable tool in the assessment of many conditions, including the challenge of diagnosing and monitoring the therapeutic progress of foot abscesses and arthritis. Alice, a superannuated female white rhinoceros is a good example of the challenges of managing large geriatric patients. The risk of anesthesia is generally higher in the large species and certainly higher in older animals. It is particularly important in these cases that the preanesthesia evaluation of the patient’s condition be as thorough as possible to plan and focus the procedures done during the anesthesia. Alice is plagued by general osteoarthritis complicated by frequent foot abscesses that require careful monitoring after debridement. The use of video thermography allows veterinarians to localize abscesses and monitor the effects of therapy on the inflammatory processes (Figures 4 and 5). Frequently, developing abscesses are detected using thermography long before external signs are apparent, allowing for early intervention. Alice’s feet are also radiographed frequently to assess her osteomyelitis using a portable X-ray machine and a heavyduty acrylic sleeve constructed to protect the X-ray plate when bearing the full weight of the rhinoceros. Alice is coaxed to stand in position on the acrylic sleeve using a combination of food and tactile rewards. White rhinoceroses are not particularly food motivated, but they love to be scratched and rubbed.
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Case: sea turtle head trauma Zoological imaging is not limited to the medical management of captive wildlife. Important conservation species such as the endangered sea turtles also benefit from diagnostic imaging. Trauma, often inflicted by unfortunate encounters with boats and propellers is one of the most common reasons a sea turtle might find itself on an imaging gantry. A84456 is a loggerhead sea turtle that stranded on the North Carolina coast and was fortunate enough to be taken to a sea turtle rescue hospital for stabilization. Although the severe trauma to the skull was certainly evident without the aid of imaging, careful 3D reconstructions of CT images (Figure 6) allowed surgeons to assess the turtle’s prognosis and then to plan a successful repair of the trauma. A raised bridging system of plastic plates successfully stabilized the skull and after a year long recovery, rerelease into the wild is in this turtle’s future. Case: lemur with a swollen face Zoological species can have very unusual anatomy, which in turn can make it important to be very conservative in interpreting diagnostic images. Poe, a wild caught male Aye Aye is a case in point. One of very few Aye Ayes ever held in captivity, Poe is an important part of the conservation research efforts of the famous Duke University Lemur Center. Captured in the wild in 1987 when he was estimated to be a year old, Poe is at least Figure 7. Poe, an adult male Aye Aye at the Duke Lemur Center. Note the unusual forefinger and large ears used in detecting grubs burrowing in trees (photo courtesy of David Haring, Duke Lemur Center).
Figure 6. A 3D reconstruction of a computed tomography examination of loggerhead sea turtle A84456, which stranded on the North Carolina coast after being hit by a boat propeller. Reconstructive surgery and over a year of recovery and rehabilitation repaired the defects. Color illustration online. 86
23 years old and perhaps older. A medium-sized prosimian of dramatic appearance (Figure 7), Poe has very large ears, a highly modified jaw, and tooth structure, and a very unusual extremely elongated third digit with a 360-degree range of motion facilitate a life style of detecting, capturing, and feeding on insects boring deep in wood. When Poe was presented to the Lemur Center veterinarians for a swollen face, a diagnosis of a retrobulbar abscess was made, potentially because of dental problems. However, despite appropriate culture and sensitivity testing, antibiotic treatment, and a tooth extraction, the problem did not resolve completely. An exploratory surgery to follow a fistulous tract in the mandible was performed to rule out the presence of a foreign body or sequestrum. None were found. Extensive postsurgical treatments did not resolve the infection, and the challenging nature of the case led to an MRI study of Poe’s head (Figure 8). On T2-weighted images, regional hyperintensity in the soft tissue adjacent to the left ramus
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Figure 8. Magnetic resonance imaging of Poe the Aye Aye: T1, T2, and T1 C gadolinium contrast-medium images. Transverse plane images are analogous to the coronal view and dorsal plane images are analogous to axial view in humans. On the T2 image, there is regional hyperintensity in the soft tissue adjacent to the left ramus of the mandible that is most severe laterally. The left masseter and pterygoid muscles are enlarged. With contrast medium, there is intense, regional enhancement surrounding the left ramus of the mandible medially and laterally, extending dorsally toward the condylar process. Dorsal plane images depict the rostrocaudal extent of this lesion.
of Poe’s mandible that was most severe laterally was noted, indicating edema and inflammation. The left masseter and pterygoid muscles were enlarged. After administration of gadolinium contrast medium, there was intense, regional enhancement surrounding the left ramus of the mandible medially and laterally, extending dorsally toward the condylar process suggesting osteomyelitis of Poe’s left temporomandibular joint. Aggressive antibiotic therapy using Azithromycin seemed to resolve the condition for some time, but over the next 4 years facial swelling has recurred several times, affecting both sides of Poe’s face. Extensive culture-guided antibiotic therapy including the use of embedded antibiotic laden pleuronic gel and surgical interventions including dental modifications guided by plain film radiography have only temporarily halted the condition. During the process of managing Poe’s case, we have learned that the unusual continuously growing incisors of the Aye Aye stop growing late in life. How this may relate to Poe’s condition is unknown, VOLUME 31 ISSUE 3
but Poe’s veterinarians continue to treat flares of the condition as they arise and work to provide Poe with a good quality of life, while seeking the underlying cause of the condition. Case: gorilla radiotherapy Captive wildlife tend to live much longer than they would in the wild and as a result many zoos manage what would be considered to be geriatric collections. As a result, cancer is a common problem that must be dealt with by zoological clinicians. This is particularly true for mammals, and one informal survey in a major zoo found some form of cancer present in nearly half of all mammals that were necropsied over a series of years. Veterinary oncologists have researched and developed therapeutic approaches to many types of cancer over the years and both curative and palliative therapies, including radiation therapy will be applied to zoological species when a reasonable plan that balances the
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Figure 9. Katie, the gorilla being positioned on the gantry before imaging to guide design of her radiation therapy (photo courtesy of E. Stringer).
challenges of managing the animal for treatment and concerns about quality of life can be achieved. Katie, a 36-year-old female western lowland gorilla was examined by veterinarians at the North Carolina Zoological Park for intermittent vaginal bleeding (Stringer et al., 2010). Plain film radiographs were not informative, but vaginoscopy revealed a thickened vaginal mucosa and biopsies were diagnosed and differentiated squamous cell carcinoma. Abdominal ultrasound showed a heteroechoic mass 7 cm in diameter in the area of the uterus, and thoracic radiographs showed no evidence of metastasis. CT of the abdomen, pelvis, and thorax was performed with the patient supine in a Vacloc positioning device to facilitate repeatable positioning (Figure 9). Both pre- and postcontrast series were obtained. CT could not distinguish the ovaries and revealed the locally invasive mass involved in the uterine body and horns and extended caudally through the cervix and into the vagina (Figure 10). There were no signs of metastasis and a decision was made to
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proceed with palliative radiation treatment using CT-based computerized treatment planning software (Figure 11). Katie was managed in a large custom gorilla squeeze cage and anesthetized for each treatment. A total dose of 16 Gy was delivered in four fractions of 4 Gy given two per day 6 hr apart, for two consecutive days. After treatment, Katie had decreased appetite and lethargy for approximately 2 weeks but recovered well. Reevaluation of the tumor by CT examination 8 weeks later indicated a modest response to therapy and the continued lack of evidence of metastasis. The decision was made to administer a second round of palliative radiation therapy to Katie. She tolerated this round better than the first, with no signs of inappetence or lethargy. Katie was then allowed to live her life in her naturalistic exhibit at the NC Zoological Park, being monitored daily for quality of life. After several months, Katie’s condition began to deteriorate and she was humanely euthanized. DISCUSSION Zoological radiologists use any available imaging technique to facilitate the diagnosis and treatment of their very special patients. The nature of the patients poses some interesting challenges, both logistically and in obtaining and interpreting the images. Special views that would not be routine in human radiology help compensate for anatomic differences. A good example is the routine use of anterior-posterior views for examination of turtles, particularly those suspected to have pulmonary lesions. This view, which would be singularly unproductive in human radiology obtains a clear view of the lungs of turtles without interference of other organs. The lungs of turtles are dorsal to all of the underlying viscera, making an anterior to posterior
Figure 10. Katie, the gorilla’s computed tomography images: transverse and dorsal images with iodinated contrast medium. A spherical, multilobed, and cavitary mass extends to the right from the remnant of the uterine corpus, which is invaded by the tumor near the cervix. 88
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with very different expertise and experience. As the available equipment and modalities continue to evolve and become available to zoological institutions, the management of the health of wildlife of all types is greatly enhanced.
References
Figure 11. Katie, the gorilla being positioned for radiation therapy (photo courtesy of E. Stringer).
orientation of the beam particularly useful for showing lung fields. In some cases, unusual measures are used to simulate standard human positioning. An example would be for thoracic imaging of primates. Because nonhuman primates have to be anesthetized for radiography, it would be natural to position them in recumbent positions used for other animals. However, these positions result in organ relationships that are quite different from those obtained in standing positions used routinely to obtain human chest films. The similarity of primate anatomy to human anatomy, and the often much greater experience of human radiologists reading chest films have made it common practice to consult with human radiologists on reading these cases. To optimize the ability of human radiologists to interpret nonhuman primate films, it is routine for zoological radiologists to literally hang anesthetized primate patients from their arms to try and simulate the standard standing films taken of humans. This works reasonably well for small- and even medium-sized primates, but not for the large apes. The size of patients can present challenges. Large adult gorillas challenge the weight limits of normal imaging gantries, and bore diameters of some advanced imaging techniques can only accommodate extremities of some zoological patients, even when special heavyduty gantries are available. For very small patients, the challenge is in providing images with adequate resolution to allow their enlargement for careful assessment. Digital imaging equipment has gone a long way to solve the problem of enlargement of images of very small patients that otherwise could only be adequately imaged with special equipment with very narrow tube focal apertures. With all of the challenges, zoological radiology is an intellectually stimulating field that is very definitely a team sport, requiring the collaboration of individuals VOLUME 31 ISSUE 3
Berzins, I.K., Maslanka, P., Montali, R.J., Davis, K.J., Pletcher, J.M., & Stoskopf, M.K. (1990). Anatomy and histology of the common cuttlefish, Sepia officinalis. Washington, DC: Armed Forces Institute of Pathology Study Set. Blackband, S.J., & Stoskopf, M.K. (1990). In vivo nuclear magnetic resonance imaging and spectroscopy of aquatic organisms. Magnetic Resonance Imaging, 8(2), 191-198. Capello, V., Lennox, A.M., & Widmer, W. (2008). Clinical radiology of exotic companion mammals. Wiley-Blackwell. Gage, L. (2006). Radiology. Fowler, M., Makota, S. The biology, medicine and surgery of elephants: Blackwell Publishing, pp. 192-198. Hahulski, G., Marcellin-Little, D.J., & Stoskopf, M.K. (1999). Morphologic evaluation of rotated tibiotarsal bones in immature ostriches (Struthio camelus). Journal of Avian Medicine and Surgery, 13(4), 252-260. Huml, R.A., Khoo, L.H., Stoskopf, M.K., & Forrest, L.J. (1993). Radiographic diagnosis. Veterinary Radiology and Ultrasound, 34(3), 178-180. Kaiser, G.W. (2008). The inner bird: Anatomy and evolution. University of Washington Press. Krautwald, M. (1995). Atlas of radiographic anatomy and diagnosis of cage birds. Blackwell. Krautwald-Junhanns, M., Pees, M., Reese, S., & Tully, T. (2001). Diagnostic imaging of exotic pets: Birds, small mammals, reptiles. Schluetersche. Love, N.E., Douglas, J.P., Lewbart, G.A., & Stoskopf, M.K. (1996). Radiographic and ultrasonographic evaluation of egg retention and peritonitis in two green iquanas, Iquana iguana. Journal of Veterinary Radiology and Ultrasound, 37(1), 68-73. McSweeney, T., & Stoskopf, M.K. (1988). Selected anatomical features of the neck and gular sac of the brown pelican (Pelecanus occidentalis). Journal of Zoo and Wildlife Medicine, 19, 116-121. McSweeney, T., & Stoskopf, M.K. (1989a). Limb anatomy of the brown pelican (Pelecanus occidentalis). Journal of Zoo and Wildlife Medicine, 20(2), 191-198. McSweeney, T., & Stoskopf, M.K. (1989b). Selected features of the abdominal and thoracic anatomy of the brown pelican (Pelecanus occidentalis). Journal of Zoo and Wildlife Medicine, 20(2), 184-190. Samour, J., & Naldo, J.L. (2007). Veterinary diagnostic imaging: Birds, exotic pets and wildlife. Saunders Ltd. Silverman, S., & Tell, L. (2004). Radiology of rodents, rabbits and ferrets: An atlas of normal anatomy and positioning. Philadelphia, PA: W.B. Saunders. Silverman, S., & Tell, L. (2009). Radiology of birds: An atlas of normal anatomy and positioning. Saunders. Stoskopf, M.K., Fishman, E., & Williams, T. (1990). Volumetric imaging for three-dimensional display of the skeletal anatomy of the sea otter. Veterinary Radiology, 31(3), 142-145. Stoskopf, M.K., & Herbert, D. (1990). Selected anatomical features of the sea otter (Enhydra lutris). Journal of Zoo and Wildlife Medicine, 21(1), 36-47.
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Stoskopf, M.K., & Oppenheim, B.S. (1996). Anatomical features of Octopus bimaculoides and Octopus digueti. Journal of Zoo and Wildlife Medicine, 27(1), 1-18. Stringer, E.M., DeVoe, R.S., Valea, F., Toma, S., Mulvaney, G., & Pruitt, A., et al. (2010). Medical and surgical management of reproductive neoplasia in two western lowland gorillas (Gorilla gorilla gorilla). Journal of Medical Primatology, 39, 328-335. Webb, T. & Ireland, J. (2010). Dietary practices for hand-rearing of infant chimpanzee (Pan troglodytes) at the North Carolina
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zoo (abstract). Sixth Crissey Zoological Nutrition Symposium, Raleigh, NC; pp. 27. Willens, S., Dupree, S.H., Stoskopf, M.K., Lewbart, G.A., Taylor, S.K., & Kennedy-Stoskopf, S. (2006). Measurements of common iliac arterial blood flow in anurans using doppler ultrasound. Journal of Zoo and Wildlife Medicine, 37(2), 97-101. Williams, J. (2004). Diagnostic imaging of avian and exotic animals. Iowa State Press.
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