Ultrasonographic features of the normal thyroid gland in adult horses

Abstract

Few reports have been published regarding the use of ultrasonography as a method of evaluating the normal thyroid gland in horses. For these reasons, this study aimed at determining reliably of the thyroid measurements from the comparison between the left and right thyroid lobes, as well as assessing the contour, format, echotexture and echogenicity of the healthy thyroid by mode-B ultrasonography. Additionally, the equine thyroid vascularization was quali-quantitatively characterized the by Doppler. The sample size initially was determined by the animal selection with advanced age and without volume increase in the neck proximal region. Finally, eleven horses were selected by laboratory test, search of thyroid neoformations by ultrasonography and cytology thyroid. Next, these animals were submitted to thyroid lobes ultrasonographic evaluation. Excellent reproducibility was observed for all measurements obtained. Among the comparisons made between the quantitative parameters of the left and right lobes, it was observed that there was only difference between their respective lengths. Qualitatively, there was a significant variation between the lobes elliptical format in the longitudinal plane of some glands, which oscillated between a rounded and flattened conformation. Thus, we can conclude that the difference between the lobes format of some thyroids can be explained by the significant difference observed between the length of the left and right lobes. Additionally, it was verified that there was no difference between the Doppler quantitative parameters. Therefore, we may suggest that unilateral analysis of the cranial thyroid artery by spectral Doppler can be used to evaluate equine thyroid diffuse disorders.

Diagnostic imaging and conservative management of an ultimobranchial thyroid cyst in an adult horse

“…However, the cystic mass content and its nature were poorly characterised radiographically. Due to the excellent representation of soft tissue pathology by ultrasonography, it is commonly used as a complementary diagnostic modality to radiography to identify the content of soft tissue masses (Davies et al., 2010; Viana et al., 2019). Horses with thyroid enlargement may show clinical signs of respiratory noise and gulping due to external compression of the larynx or trachea, loss of form, or restricted movement of the head and neck (David et al., 2008).…”

“…In the literature, pharyngeal endoscopy and ultrasound examination accompanied by plain or contrast radiography have been described in thyroid cystic masses in horses (Rinnovati et al., 2018). By using ultrasonography, a comparison of the size between the left and right thyroid lobe can be easily made (Viana et al., 2019). However, neither ultrasonography nor contrast radiography can identify the exact size of the cyst and more importantly, the relationship between the cyst and adjacent vital organs.…”

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The equine thyroid gland is a bilobed organ, which is located in the dorsolateral aspect of the third to sixth tracheal ring (Viana et al, 2019). The embryonic ultimobranchial body is an outpocketing of the fourth pharyngeal pouch that fuses with the thyroid diverticulum, giving rise to calcitonin-producing C-cells (David et al, 2008;Saulez et al, 2012).

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Assessment of qualitative and quantitative parameters of healthy thyroid gland in adult horses by magnetic resonance imaging

“…In retrospective studies, ultrasonography of the equine thyroid provided good spatial resolution, making it suitable for evaluating the normal parameters, as well as identifying tumours. (Davies et al., 2010; Perez‐Ecija et al., 2017; Saulez et al., 2013; Viana et al., 2019). However, this technique has some limitations, including: the skill of the operator; the inability of ultrasonography to assess the deep structures of the neck, such as the skull base; limited detection of retrotracheal extension of an enlarged thyroid, due the acoustic impedance caused by air in the trachea or adjacent bones; and difficulty in confirming thyroid origin of large neck masses that distort the anatomy (Loevner et al., 2008; Taeymans et al., 2008).…”