Thyroid and parathyroid glands | BSAVA Library

Thyroid and parathyroid glands

image of Thyroid and parathyroid glands
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The indications for ultrasonography of the thyroid and parathyroid glands include: the presence of a space-occupying lesion of unknown origin; to differentiate solid from cystic thyroid masses; to stage a thyroid mass; to search for ectopic thyroid tissue; to document primary hyperthyroidism in dogs; to document a goitre; treatment planning and monitoring of thyroid tumour; and hypercalcaemia. This chapter explores the value of ultrasonography compared with radiography and advanced imaging techniques. Imaging technique and normal ultrasonographic appearance are explained followed by thyroid gland and parathyroid gland abnormalities. This chapter contains two video clips.

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Image of 19.1
19.1 Longitudinal image of the left thyroid lobe (between the callipers) in a healthy Beagle. The thyroid lobe has a rounded cranial pole and a pointed caudal pole. Note the homogeneous, hyperechoic gland parenchyma compared with the surrounding musculature, and the hyperechoic smooth capsule. E = oesophagus; St = sternothyroid muscle.
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19.2 Transverse image of the left thyroid lobe (between the callipers) in a healthy Beagle. The thyroid lobe has a polygonal to almost triangular shape. C = common carotid artery; E = oesophagus; Sc = sternocephalic muscle; Sh = sternohyoid muscle; St = sternothyroid muscle; T = trachea.
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19.3 Longitudinal image of an external parathyroid gland (between the callipers) in a healthy dog. The gland measures 2 mm. E = oesophagus; T = thyroid lobe.
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19.4 Transverse and longitudinal images of a thyroid lobe (between the callipers) of a dog with primary hypothyroidism. The lobe is mildly decreased in size, is isoechoic to almost hypoechoic compared with the surrounding muscles, has a heterogeneous parenchyma, an undulating and ill defined capsule, and has a rounded shape on transverse section. C = common carotid artery; St = sternothyroid muscle; T = trachea.
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19.5 Longitudinal image of an adenoma in the right thyroid lobe (between the callipers) in a cat. Note the multiple anechoic areas in the cranial aspect of the diffusely enlarged lobe. The remainder of the lobe is normal in echotexture and echogenicity. Power Doppler indicates mildly increased vasularization within the gland. The larger blood vessels at the cranial and caudal poles of the thyroid lobe represent the normal cranial and caudal thyroid arteries and veins.
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19.6 Longitudinal image of a compact cellular thyroid carcinoma of the right thyroid lobe in a 10-year-old Golden Retriever. The lobe contains multiple areas of dystrophic mineralization, suggesting the malignant nature of this neoplasm. Note the multiple anechoic areas of necrosis throughout the gland parenchyma. No capsule disruption or local tissue invasion were detected. The lobe measured 24 mm × 11 mm.
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19.7 Longitudinal image of a thyroid lobe (between the callipers) containing a cyst. The cyst was noted in a dog being treated for primary hypothyroidism. Note the faint distal enhancement dorsal to the cyst (*), together with side lobe artefacts (arrowheads).
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19.8 Longitudinal images of the left and right thyroid lobes with the corresponding external and internal parathyroid glands (between the callipers) in a 9-year-old Weimaraner with renal secondary hyperparathyroidism. The largest parathyroid gland measures 7.0 mm, the smallest measures 3.5 mm.
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19.9 Longitudinal image of the left external parathyroid gland (between the callipers) in an 11-year-old Samoyed with primary hyperparathyroidism. The parathyroid gland measures 8 mm. Note the mildly increased echogenicity of the lesion compared with the normal parathyroid tissue. Histopathology confirmed the lesion was an adenoma.


Normal thyroid gland (1).

This clip shows the left thyroid lobe in a longitudinal plane. At the start of the clip a longitudinal section through the left common carotid artery is seen. As the transducer is moved from lateral to medial, the normal thyroid lobe is seen ventral to the oesophagus. Note the fusiform shape of the lobe and its hyperechoic appearance compared with the more ventrally located neck musculature. At the end of the clip a longitudinal section of the trachea is seen, with the luminal air producing acoustic shadowing.

Normal thyroid gland (2).

This clip shows the left thyroid lobe in a transverse plane. The transducer is moved from cranial to caudal, showing a normal thyroid lobe ventral to the oesophagus, located in between the trachea and the common carotid artery. Note the triangular shape of the gland, its homogeneous hyperechoic parenchyma compared with the ventral neck musculature, and its smooth hyperechoic capsule.

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