Advanced Diagnostic Imaging in Pet Birds and Exotic Pets

By Elisabeth Simone-Freilicher, DVM, DABVP (Avian Practice)
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While advanced diagnostic imaging such as ultrasound, echocardiography, and CT are commonly used in canine and feline patients, size and unique anatomic features of non-domestic pets means these valuable tools are often underutilized in birds, reptiles, and exotic small mammals.

Birds

The small size and presence of coelomic air sacs can limit the utility of ultrasonography in pet birds. However, when ascites is present, the free coelomic fluid frequently compresses the air sacs, improving visibility and utility of coelomic ultrasound even in a patient as small as a budgerigar. (Figure 1)

Coelomic ultrasonography can also be useful in identifying developing or minimally shelled eggs which may not be mineralized enough to be obvious on radiographs. Pre-ovulatory large follicles can also be identified prior to administering a GnRH agonist, which is contraindicated near ovulation, as dystocia may occur. (Figure 2)

Echocardiography can also be performed to identify cardiac chamber enlargement, valvular disease, and pericardial effusion. Although the presence of a broad keeled sternum and narrow rib space often preclude use of the same intercostal approach used in small animal cardiology, angling the probe either cranially through the liver (hepatic window), or caudally at the thoracic inlet is often rewarding.

Computer-aided tomography is also gaining increased utility in avian medicine. Today’s CT machines are so rapid that often whole body CT-scans can be performed on a bird using sedation alone, rather than full anesthesia. This is frequently appealing to owners, who may be understandably wary of anesthesia for their pet birds if it can be avoided, and is a distinct advantage when a sick bird is assessed as unstable for anesthesia. In addition to masses (Figure 3), organomegaly, and dilation or thickening of gastrointestinal organs, CT can be used to identify GI foreign bodies composed of wood or plastic, which radiographs can miss. Metabolic bone disease and peripheral atherosclerosis may also be identified for treatment.

Figure 1. Ultrasound of a coelomic mass in a budgerigar- this lobulated soft tissue mass was able to be identified as the cause of ascites and coelomic distention in this 28-gram bird.	Figure 2. A point-of-care coelomic ultrasound prior to administering Lupron. The “bullseye” ova can be clearly seen.
Figure 3. CT of an Amazon parrot with a cloacal soft tissue mass.

Reptiles

Coelomic ultrasonography can be used in much the same fashion as in birds, with less interference from air sacs, although these structures do exist in some species. (Figure 4). CHF has been identified in reptiles using echocardiography, and may respond to treatment to temporarily restore quality of life. (Figure 5) CT can be particularly useful in identifying masses, or gastrointestinal thickenings or blockages, especially in large reptiles where coelomic ultrasound might be challenging. (Figure 6)

Figure 4. Coelomic ultrasound showing a hepatic cyst in a Leopard gecko.	Figure 5. Pericardial effusion in a bearded dragon with CHF.
Figure 6. CT of coelomic soft tissue mass in a red-tailed boa constrictor.

Exotic mammals

Ultrasound and echocardiograms are often performed in ferrets to detect neoplasia and heart disease; however, it is often under-utilized in small herbivores such as rabbits, chinchillas, and guinea pigs. Liver lobe torsion has been well described in rabbits, and relies on abdominal ultrasound with color-flow Doppler to diagnose. While gas present in the small herbivore cecum can interfere with a thorough abdominal ultrasonographic examination, gastric outflow obstructions can often be identified or ruled out, as well as intussusceptions, intestinal obstructions, and normal or abnormal intestinal motility. Kidneys, ureters, bladder, and urethra can also be assessed (Figure 7) and ultrasound-guided cystocentesis can be performed for urinalysis. Echocardiography is performed as in cats, and as in domestic pets, early identification of heart disease can guide treatment to preserve quality of life for as long as possible.

CT can be especially useful in identifying cranial bullae disease, which may escape detection via radiographs alone. In cases of facial abscesses, tooth root involvement can be identified and pinpointed to indicate whether dental extractions are needed to increase the odds of a successful surgical outcome. Chronic or recurrent upper respiratory infections can benefit from a CT scan of the sinuses and maxillary molars, identifying underlying causes that may be resistant to antibiotic therapy alone. (Figure 8) Additionally in rabbits, thymomas may be identified using CT, sampled for cytology via ultrasound guided FNA, and treated using radiation therapy. Contrast CT has been described in pet rats to identify pituitary tumors thought to be the underlying cause of mammary fibroadenomas and associated with hind limb ataxia in older rats. (Figure 9)

Diagnostic imaging advances in recent years have greatly benefitted our avian and exotic patients, allowing for smaller patients to be imaged more quickly, minimizing risk of handling and anesthesia. This allows us to make better antemortem assessments, and helps our clients to make more informed decisions regarding treatment and palliative care.

Figure 7. Abdominal ultrasound showing a severely thickened bladder in a rabbit.	Figure 8. CT of a sinus granuloma in a rabbit with chronic upper respiratory signs.
Figure 9. CT of a pituitary tumor in a pet rat with a mammary fibroadenoma.

References

• Hoppes, Sharman. Foreign Body Perforation of the Proventriculus of an Umbrella Cockatoo. Conference of the Association of Avian Veterinarians, Washington, DC, 2017.
• Echols, Scott. Avian Metabolic Bone Diseases. Conference of the Association of Avian Veterinarians, Washington, DC, 2017.
• Simone-Freilicher, Elisabeth, Sullivan P, Quinn R, et al. Two Cases of Congestive Heart Failure in Lizards. Conference of the Association of Reptile and Amphibian Veterinarians, ExoticsCon, San Antonio, TX, 2015.
• Graham, Jennifer E. Liver Lobe Torsion in Rabbits: 16 cases. Journal of Exotic Pet Medicine. Volume 23, Issue 3, July 2014, Pages 258-265
• Simone-Freilicher, Elisabeth, Noonan B, Tsai S, et al. Contrast CT for the Detection of Pituitary Tumors in Rats. Conference of the Association of Exotic Mammal Veterinarians, ExoticsCon, Portland, OR, 2016.