COMPUTED TOMOGRAPHIC CHARACTERISTICS OF THE THYROID GLANDS IN EIGHT HYPERTHYROID CATS PRE- AND POSTMETHIMAZOLE TREATMENT COMPARED WITH SEVEN EUTHYROID CATS

Tomographic and ultrasound evaluation of the thyroid gland in pet guinea pigs

There has been increasing interest in the literature on primary thyroid diseases in guinea pigs, which are believed to be underdiagnosed. This study describes the size and characteristics of the thyroid gland on ultrasound (US) and CT examinations in the guinea pig (Cavia porcellus) without evidence of thyroid pathology and examines the possible use of US as a routine examination for thyroid diseases. This prospective and anatomical study included 20 guinea pigs that underwent CT for dental pathologies and US for thyroid gland (TG) examination. Based on US and CT images, this study evaluated the thyroid lobe dimensions (length, height, and width) and shape. Echogenicity and homogeneity were assessed on US images, and attenuation values (HU) and homogeneity were evaluated on CT images. All animals underwent CT and US examinations under anesthesia. Thyroid lobes appeared more frequently as fusiform on CT (65%) and oval on US scans (67.5%). The attenuation values on CT scans were homogeneous. On the US scans, the TG was more frequently hypoechoic. No statistically significant differences were found between the size of the right and left thyroid lobes, both with CT and US. A statistically significant difference was found between the length values on CT and US. The US and CT thyroid gland dimensions, shape, and appearance were described. Both CT and US are useful techniques for evaluating the TG in guinea pigs.

CT appearance and measurements of the normal thyroid gland in goats

Background

Goats are increasingly being kept as companion animals, thus their owners expect advanced medical care, including modern diagnostic imaging. Computed tomography (CT) is now widely used in veterinary medicine, in both clinical practice and for scientific purposes. So far, the CT appearance of various body parts has been described in goats, but reports on thyroid gland CT are still lacking. The thyroid gland in goats may become enlarged due to dietary, genetic or neoplastic disorders. CT examination, as in other animals and humans, could aid in the diagnosis of thyroid diseases in goats and could be used for research purposes. The aim of the study was to present the CT characteristics of the normal caprine thyroid gland, in particular its dimensions, volume and density.

Results

Fifty-seven goats were included in the study. None of the animals had clinical, CT, post-mortem or histopathologic abnormalities in the thyroid gland. CT features of the thyroid gland were determined, such as dimensions, volume, density, location and shape. The presence of the thyroid isthmus and ectopic thyroid tissue was also assessed. The gland was visible in every animal as two homogenous, highly attenuating, well-circumscribed lobes located in the most cranial part of the trachea. The mean dimensions of the thyroid lobe were 30.3 × 12.7 × 6.7 mm, the mean density was 80.9 Hounsfield Units (HU) and the mean volume was 1.32 cm³ or 1.39 cm³, depending on the method used. Also, the internal parathyroid glands were visible in some animals.

Conclusions

For the first time, the normal CT appearance of the thyroid gland has been presented. CT clearly shows the thyroid gland in goats and therefore can be used in clinical practice and for research. The results of the current study may serve as a radiological guideline for practitioners and may be the basis for further CT studies on normal and diseased caprine thyroid glands.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03047-w.

Pre-contrast CT attenuation of the thyroid gland is lower in brachycephalic dogs versus non-brachycephalic dogs

Computed tomography has been used in human medicine to evaluate the thyroid gland functional status by means of Hounsfield units (HU). Studies describing attenuation value abnormalities, other than those in thyroid neoplasia, lack in veterinary medicine. The authors have observed a subjective reduction in thyroid attenuation in some patients undergoing CT for reasons other than thyroid disease. This finding has been identified more frequently in brachycephalic breeds compared to non-brachycephalic breeds. In order to determine the thyroid gland attenuation variability on CT, a retrospective and prospective, analytical, cross-sectional study was performed. The thyroid attenuation values of 65 client-owned dogs were assessed using a 16-slice helical CT scanner. Differences in attenuation between brachycephalic and non-brachycephalic dogs were estimated by Welch's t-test. Serum TT4 and TSH levels were available in 26 patients. Statistically significant differences were observed in the pre-contrast attenuation value ranges between brachycephalic and non-brachycephalic dogs (P = .04). The pre-contrast attenuation value range for the brachycephalic group was 69.1-108 HU while being 75.8-121 HU for the non-brachycephalic group. No significant correlation was found between thyroid attenuation and serum thyroid hormone levels in our population (P > .6). All patients with hypoattenuating thyroid were brachycephalic and reported euthyroid. In conclusion, brachycephalic dogs seem to have a pre-contrast attenuation thyroid gland range lower than non-brachycephalic dogs. The present study contributes to the veterinary literature by providing a new thyroid attenuation value range for brachycephalic breeds. Additionally, hypoattenuating thyroid glands may be found in dogs with normal TT4 and TSH values.