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.