Diagnostic Imaging for Assessment of the Endocrine System in Exotic Animals

Greta Doden, Alexandre B. Le Roux, João Brandão

Background
The endocrine system in exotic animals plays a vital role in regulating hormonal functions like glucose and calcium metabolism, reproductive activity, stress response, and thyroid regulation. Endocrine disorders, such as adrenal gland disease in ferrets or calcium dysregulation in reptiles and birds, are prevalent. Diagnostic imaging is an essential tool for identifying and managing these conditions, providing insight into the anatomical and pathological states of various endocrine organs.

Methods
The review highlights the utility of various imaging modalities for diagnosing endocrine disorders in exotic species, organized by technology:

-Ultrasonography: A real-time, cost-effective imaging tool, particularly useful for soft tissue evaluation.

-Radiography: Common for detecting bone density changes and large masses but limited by superimposition in small animals.

-Computed Tomography (CT): Provides detailed, cross-sectional imaging for staging and surgical planning.

-Magnetic Resonance Imaging (MRI): Optimal for soft-tissue detail, including brain and pituitary evaluations, though costly and requiring anesthesia.

-Nuclear Scintigraphy: Useful for functional imaging, particularly thyroid assessments.

-Positron Emission Tomography (PET): Primarily applied in research or oncology cases.

Results
Imaging applications varied by species:

-Ferrets: Ultrasonography is the gold standard for adrenal gland diseases and insulinomas. CT and MRI assist in detecting smaller or metastatic lesions.

-Rabbits: Ultrasonography and CT are used for diagnosing ovarian pathology, pituitary adenomas, and rare adrenal diseases.

-Rodents: Ovarian cysts in guinea pigs are commonly identified via ultrasound, while CT/MRI is useful for pituitary and adrenal evaluations.

-Birds: Radiography aids in reproductive and bone health assessments, with CT and MRI providing insight into reproductive tumors and metabolic disorders.

-Reptiles: Ultrasonography and CT are key for evaluating reproductive status and endocrine-related neoplasia. Bone changes from metabolic diseases are evident on radiographs.

-Amphibians and Fish: Limited applications, with ultrasonography and CT primarily used for reproductive and bone assessments.

Limitations
-Imaging sensitivity and specificity are species-dependent, influenced by anatomical challenges like air sacs in birds or small organ size in amphibians.
-Operator skill, cost, and the need for anesthesia impact the feasibility of certain modalities.
-Limited data exist on some species, requiring extrapolation from closely related animals or laboratory models.

Conclusions
Diagnostic imaging is indispensable for the management of endocrine diseases in exotic animals, often requiring multimodal approaches tailored to species, disease, and client constraints. Ultrasonography and CT are most commonly utilized, while nuclear scintigraphy and PET have niche roles. Advancements in imaging technology and accessibility may expand its utility in clinical exotic animal medicine.

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