Ultrasonographic examination of selected small structures in dogs and cats: thyroid glands, lymph nodes and adrenal glands

Ultrasonography has become an important imaging modality for the evaluation of small structures, such as thyroid glands, lymph nodes and adrenal glands, because it is relatively inexpensive, it is non-invasive and it does not require general anesthesia. Both normal and abnormal small structures can be seen, though this depends to a great extent on the quality of the equipment and the operator skills. For thyroid glands, it can be used to assess thyroid carcinomas, canine hypothyroidism and feline hyperthyroidism. Ultrasonography is also a very valuable modality for evaluating superficial and abdominal lymph nodes. By combining different ultrasonographic criteria, it is possible to accurately differentiate normal from reactive or malignant lymph nodes. Finally, the adrenal glands can be evaluated ultrasonographically in cases of hyperadrenocorticism (pituitary- or adrenal-dependent), hyperaldosteronism, hypoadrenocorticism and adrenal neuroendocrine tumors.