The Wild Side of Diagnostic Imaging

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Dr Annie Mears BVM BVS BVMedSci

Ikhala Veterinary Wildlife Services - Grahamstown, Eastern Cape

Working with wild animals is an incredible privilege, it is humbling, aweinspiring, character building and also a heart racing, sweat-producing, logistical nightmare. Practicing good medicine in wildlife in the middle of nowhere has its challenges, diagnostic imaging being one of them.

In many veterinary sectors an increase in scientific knowledge, evidence-based medicine, medical technology and availability of pharmaceutical interventions has catapulted vets into the 21st century. It’s easy to believe that wildlife practice in rural South Africa could get left behind, however, it’s not entirely the case.

Whilst working in a progressive, well-equipped wildlife practice, surrounded by the Eastern Capes most well-known private and stateowned game reserves, it’s clear to see exciting steps forward. On an average day, we perform the routine services most wildlife vets are familiar with; several angry buffalos in a boma, a sickly sable and some flighty nyala. On the other days we load up our portable biochemistry, haematology and blood gas analysis machines, a team of vets and nurses and our precious DR X-ray machine into a fleet of bakkies and we respond in preparation for the calls we dread most; several rhino have been poached at a nearby reserve, one is still alive.

Portable biochemisty machine

Figure 1: Advanced diagnostics including portable biochemistry machine (Abaxis) have revolutionised care.

The extent of the rhino poaching crisis is well known amongst our profession and the use of patient-side diagnostics is revolutionising veterinary care of our rhino. The cost of this equipment places it out of reach of most wildlife practices, and it has only been through the incredible support of Medivet UK, BCF (now IMV Imaging) and Abaxis that we have been able to build this capacity through Wilderness Foundation Africa.

Digital radiography allows us to quickly identify fractures and locate bullets in deep wounds. However, it’s use in wild animals does not come without complications. 

In small game, radiography is not dissimilar to that of your domestic animals, similar settings and views can be achieved with conventionally diagnostic views easily achievable. 

Figure 2: Lateral fetlock radiograph of an adult sable bull taken with DR

Radiography in your average 1.2 tonne, injured white rhino presents us with numerous challenges. The first and most obvious challenge is positioning for that perfect shot. The rhino is lying in lateral recumbency after darting, he has a possible gunshot wound to his right hind leg and he’s paddling his feet. The use of butorphanol and midazolam in the first few minutes of anaesthesia allows us to lighten the plane of anaesthesia, improving oxygenation and perfusion, whilst maximising muscle relaxation for radiography. Achieving diagnostic images takes time, supplementation of high flow nasal oxygen can be considered, heart rate, respiratory rate and blood oxygenation should be carefully monitored. Rotating body position every 10-20 minutes helps alleviate pressure on extremities and reduces the risk of post anaesthesia myopathy/neuropathies.

Considering our rhino with the foot wound, most views of the lower limb can be taken with the animal in recumbency. However, if movement blur or anaesthetic risk is a concern allowing the rhino to stand using diprenorphine can allow weight bearing views with limited movement. An inherent problem with using a portable X-ray machine is user movement and it is not always possible to rest the X-ray machine on an object whilst taking the image.

 Lateral Fetlock

In larger species, proximal limb, body and head injuries are notoriously difficult to image due to the depth of the anatomical structures. There are few validated exposure settings for rhino, or wildlife in general, so trial and error is key.

When imaging larger structures such as the proximal limb or skull, increasing your exposure settings alone is unlikely to produce a diagnostic radiograph. For these cases, we find that the oblique image is the way forward. In smaller animals a 45-degree oblique may allow you to visualise the area of interest for example in the limb, in larger animals much steeper oblique angles must be used.

Whilst you may not get a complete view of the whole bone in a view that is easily recognisable, identifying discrepancies in the surface of the bone can give you an indication of the underlying pathology (Figure 3.). Obliques can also be utilised when locating bullets as in pachyderms, like rhino, it is common for heavy-calibre bullets to pass through the body and get trapped just under the thick skin on the other side.

Figure 3: A steep oblique view of the jaw of a white rhino female with a fractured mandible taken with DR.Steep oblique

 

Figure 4: Oblique angle of a rhino skull highlighting the sinuses taken with DR.

Oblique rhino skull

As in some domestic species, it is not possible to radiograph the abdomen and chest of most wildlife species, as portable X-ray machines cannot generate a high enough mAs or kV to penetrate. In some cases, thoracic, transabdominal or transrectal ultrasound can be used where radiography cannot. With the co-sponsorship of IMV Imaging and Medivet we are fortunate to be able to use direct DR in our critical patients. Direct digital radiography is preferable in wildlife due to ease of use in the field (no CR processor so extremely portable), speed of acquisition and overall reduction in radiation required per acquisition. However, good results can be achieved in the field with CR machines and a small team to help. Invest in an inverter and with a well-constructed protective case, you can take your developer patient side. Whether you have a DR or CR system, insuring your machine is a must.

Vehicle inverter

Figure 5: CR machine in use with a developer connected to a vehicle inverter. 

In most cases, many X-rays with high exposure settings are required, and health and safety must be a concern. Lead PPE (personal protective equipment) should be worn and the number of people around the site of X-rays kept to a minimum. Cassette holders are important to enable positioning of the cassette or detector away from the operator’s body when taking an exposure. Always use the lowest exposure setting you can to achieve a good result.

As with any wildlife procedure, the secret to success lies with a good team. At least two veterinary professionals are required for a diagnostic radiographic procedure while ensuring a safe anaesthetic.

Similar to all veterinary sectors, further investment and research is still needed to validate and further our approach to diagnostic imaging in wildlife. Increases in poaching of wildlife in South Africa necessitate a counter response from veterinarians across the globe. We must further our knowledge and practical capabilities in order to provide more appropriate treatment for the animals we now find in our care.

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