Comparison of ultrasonographic characteristics of the thyroid gland in healthy small-, medium-, and large-breed dogs

Contrast-enhanced ultrasonography of the thyroid gland in healthy dogs, hypothyroid dogs and dogs with non-thyroidal illness

Diagnosis of canine hypothyroidism remains challenging, as non-thyroidal illness (NTI)-syndrome and medical treatment can influence thyroid hormone concentrations. Conventional ultrasound may give additional hints, however high interobserver variability has been described. Contrast-enhanced ultrasound (CEUS) allows detection of changes in tissue perfusion. The purpose of the present study was to assess the possible diagnostic value of CEUS regarding diagnosis of hypothyroidism. CEUS of the thyroid gland was performed in 52 healthy dogs, 16 hypothyroid dogs, and 20 NTI patients. The following perfusion parameters were calculated: Thyroid/carotid artery (TG/CA) ratios for peak enhancement (PE) and area under the curve (AUC), time to peak (TTP) and wash-in and wash-out rates (WiR, WoR) of the thyroid gland. Impact of sedation on perfusion parameters was investigated in 8 calm healthy dogs which were examined before and after sedation using midazolam and butorphanol. Significantly higher median TG/CA ratios for PE were detected for the left and right thyroid lobe in dogs with hypothyroidism (0.97/0.96) compared to healthy dogs (0.85/0.85) and dogs with NTI (0.84/0.84). AUCs were also significantly increased in hypothyroid dogs when compared to other groups. Dogs with NTI showed significantly lower WiR and WoR compared to other groups. Values for TTP were not significantly different between groups. Sedation had only impact on results of TTP which was significantly prolonged in sedated dogs. In conclusion, CEUS of the thyroid gland can provide an additional tool for diagnosis of hypothyroidism in dogs and support its differentiation from NTI. Sedation has limited impact on CEUS results.

Technical Validation of Ultrasound Assessment of the Thyroid Gland in Cattle

Little is known about thyroid diseases in ruminants, probably due to the lack of diagnosis techniques developed in this species. However, thyroid ultrasound (TU) is widely used in human and in companion animal's medicine. It is a cheap and non-invasive examination, which allows for the identification of thyroid structures or diffuse diseases. The aim of this study was to evaluate the accuracy of TU in five calves and five cows through inter- and intra-observer repeatability. The size of the thyroid gland was measured from three views: left sagittal, right sagittal and transverse; nine measurements per view. The intra-observer coefficient was calculated for each observer. For the inter-observer, the first observer was a board-certified imagist (European College of Veterinary Diagnostic Imaging diplomate), the second was a board-certified specialist in bovine and herd management (European College of Bovine Health Managementdiplomate) and the third was an in-trained veterinarian for the TU. They each scanned the thyroid gland successively, following the same method. The intra-observer variabilities for observers 1, 2 and 3 were 8.22%, 5.53%, 5.38%, and 7.18%, 8.65% and 6.36%, respectively, for calves and cows. The inter-observer variability for calves was 10.4% and for cows, 11.8%. This study confirms the feasibility of repeatable intra- and inter-observer TU-estimated measurements in cattle.

Thyroid hormones in canine pregnancy and lactation

It is believed that thyroid function has a significant effect on fertility and fetal development in mammals. So far, however, only few studies have been published about potential effects of the reproductive cycle stage on thyroid hormone concentrations in dogs. Therefore, over the course of 122 pregnant and non-pregnant cycles in healthy bitches, Thyroid stimulating hormone (TSH), free Thyroxine (fT4), total Thyroxine (tT4) and Progesterone (P4) were measured six times to assess the influence of the cycle stage and pregnancy on hormone concentrations. The aim was to evaluate established reference intervals for the thyroid hormones in a female study population. Of the 122 bitches, 98 became pregnant. Blood samples were collected during estrus, three times in pregnancy, during lactation and after weaning, or at equivalent times during and after estrus in non-pregnant dogs. No differences between pregnant and non-pregnant animals in any of the thyroid hormones were found. Hormone concentrations, however, differed significantly between the six samplings (p < .01). TSH initially declined during pregnancy, then rose again. The mean concentration of all dogs exceeded the overall upper reference limit of 0.70 ng/mL during lactation. Concentrations of tT4 and ft4 increased during the first third of pregnancy and then subsequently declined. The overall reference limits for tT4 were 0.47-3.20 μg/dL, and for fT4 4.86-29.60 pmol/L, but the reference intervals varied between the sampling dates. The observed patterns may reflect that maternal tT4 and fT4 seem to have important effects during early pregnancy, including a pronounced negative feedback effect on TSH. The initial increase and subsequent decline of tT4 and fT4 concentrations during the course of pregnancy is in accordance with findings in humans and may support the development of fetal thyroid function. The observed peak of TSH concentrations during lactation suggests that the demand for thyroid hormones in this phase is largest. Even if the underlying causes and mechanisms of thyroid regulation are not fully understood, the results of this study show relevant changes of hormone concentrations in the course of the sexual cycle and pregnancy. In that regard, cycle stage needs to be considered when assessing thyroid function in bitches.

The role of 99mTc-MIBI SPECT/CT in patients with secondary hyperparathyroidism: comparison with 99mTc-MIBI planar scintigraphy and ultrasonography

BACKGROUND

This study aimed to compare the sensitivity of ^99mTc-MIBI SPECT/CT, ^99mTc-MIBI planar scintigraphy and ultrasonography (US) in patients with secondary hyperparathyroidism (SHPT), and to explore the factors that affect the sensitivity of ^99mTc-MIBI SPECT/CT.

METHODS

In this retrospective study, forty-six patients with SHPT who underwent ^99mTc-MIBI planar scintigraphy, ^99mTc-MIBI SPECT/CT and US were enrolled. They underwent surgery within 1 month. We compared the sensitivity of the different imaging methods based on the lesions according to the pathological results. The parathyroid lesions on ^99mTc-MIBI SPECT/CT images were divided into missed diagnosis group (MDG) and non-missed diagnosis group (NMDG). We compared the lesion to background ratio (LBR), maximum diameter, volume, the mean CT Hounsfield unit values (CT_mean) and location of lesions between MDG and NMDG.

RESULTS

The sensitivity of ^99mTc-MIBI SPECT/CT, ^99mTc-MIBI planar scintigraphy and US were 70.30% versus 48.48% versus 61.82%, respectively. The sensitivity of ^99mTc-MIBI SPECT/CT combined US was 79.39%, which was higher than ^99mTc-MIBI SPECT/CT with significant difference (P = 0.000). On ^99mTc-MIBI SPECT/CT images, the LBR, maximum diameter and volume of lesions in MDG was smaller than those in NMDG with significant difference (P < 0.001). The average LBR, maximum diameter and volume of lesions in MDG and NMDG were 3.42 ± 1.28, 9.32 ± 2.69 mm, 208.51 ± 163.22 mm³ versus 6.75 ± 5.08, 15.03 ± 4.94 mm and 863.85 ± 1216.0 mm³, respectively.

CONCLUSIONS

^99mTc-MIBI SPECT/CT exhibited the highest sensitivity among the three methods. When ^99mTc-MIBI SPECT/CT combined with US, the sensitivity can be further improved. Lesions with lower MIBI uptake and smaller lesions on ^99mTc-MIBI SPECT/CT images were easily missed.

An area ratio of thyroid gland to common carotid artery for evaluating the thyroid gland size

The feasibility of ultrasonographic measurement of thyroid gland area to common carotid artery (TG:CCA) was investigated. Twenty-one healthy, 12 hypothyroid and 18 non-thyroid illness (NTI) dogs were evaluated. The area of thyroid lobe and common carotid artery in right and left sides were measured using the same ultrasonographic images in transverse plane. The average of the right and left ratio was calculated as TG:CCA. The median TG:CCA of 21 healthy dogs was 1.53, and it did not correlate either body weight or age. The median TG:CCA of 12 hypothyroid dogs was 0.81, which was significantly lower than that of 18 NTI dogs (1.81, P<0.001). If the cut off value <1.12 was used, TG:CCA indicated hypothyroidism with a sensitivity of 100%, specificity of 83%, and accuracy of 90%. Our data indicated that TG:CCA was independent of both body weight, which may contribute to consistent measurement of thyroid size. The results of this study suggest that TG:CCA is a promising tool for diagnosing canine hypothyroidism.

Ultrasonographic and anatomical examination of normal thyroid and internal parathyroid glands in goats

Ultrasonographic examination of the normal thyroid and parathyroid glands has been described for humans and many animal species. However, similar reports for goats are still missing. The aim of the study was to present ultrasound features of the normal thyroid and internal parathyroid glands in goats with the determination of their dimensions and volume, followed by a comparison of the results to the gross examination. Seventy-two goats were used in the study. The echostructure and echogenicity of the thyroid and parathyroid glands were assessed. The length, width and height of the thyroid and the length and width of the parathyroid glands were measured. The thyroid volume was calculated using the ellipsoid formula, basing on the ultrasonographic dimensions. Size and volume of the dissected thyroid glands were established grossly, followed by a histological examination. In order to accurately describe the anatomy of the thyroid, new anatomical terminology characterizing this gland was proposed. The mean dimensions of the thyroid lobes were 30.2 x 10.5 x 6.3 mm. There were no statistically significant differences between the right and left lobe. Parathyroid glands measured an average of 3.6 x 2.4 mm. The percentage Root Mean Square Error between the results of ultrasonographic and gross examination was 16.73%, 20.65% and 17.01% for thyroid length, width and height, respectively, and 46.30% for volume. In order to obtain more precise calculation of the thyroid volume, a modified correction factor for the ellipsoid formula was introduced. For the first time, the normal ultrasonographic characteristics and dimensions of the caprine thyroid and internal parathyroid glands were presented. The results may serve as a radiological reference and be the basis for further research.

Do thyroid ultrasonographic features change according to age in euthyroid dogs?

The thyroid gland was assessed by ultrasound in healthy euthyroid mixed-breed medium size dogs in different age groups. The objective was to verify ultrasonographic imaging patterns in these groups, as well as to identify possible changes in imaging features resulting from ageing. Thirty dogs - 10 young (<1 year), 10 adult and 10 elderly - without clinical signs or history of thyroid gland disease with complete blood count and thyroid function tests within the reference values were evaluated. Each thyroid lobe was examined by ultrasound for shape, size, echogenicity and echotexture. The analysis of echogenicity and echotexture was made by histogram. Thyroid volume was estimated by the equation for ellipsoid (length × width × height) π/6. The thyroid volume of the young dogs in this study had a tendency to be higher than in adult dogs (P = 0.068) and older dogs (P = 0.120). The height of the thyroid lobe in the longitudinal plane was significantly higher (P = 0.026) in young dogs compared with the other dogs. The echotexture and echogenicity had no significant differences between groups, but the echogenicity was greater in older dogs. The results point out that ultrasound imaging of the thyroid volume is influenced by age in euthyroid dogs.

Ultrasonographic assessment of the thyroid gland and adjacent anatomic structures in Indo-Pacific bottlenose dolphins (Tursiops aduncus)

OBJECTIVE

To evaluate the use of ultrasonography for thyroid gland assessment in healthy Indo-Pacific bottlenose dolphins (Tursiops aduncus), describe the ultrasonographic appearance of the thyroid gland and adjacent anatomic structures, and identify potential associations between variations in thyroid gland morphology and demographic features in this species.

ANIMALS

18 captive Indo-Pacific bottlenose dolphins.

PROCEDURES

1,404 ultrasonographic examinations of the thyroid gland and adjacent anatomic structures (eg, cervical lymph nodes, musculature, and vasculature) were performed during the > 3-year study period. Shape, echogenicity, and homogeneity of thyroid glands were assessed, and glands were categorized into morphological configurations on the basis of results of 2-D and 3-D ultrasonographic evaluation. Associations between demographic factors and thyroid gland morphology were assessed.

RESULTS

Thyroid lobes appeared elliptical or fusiform in the transverse scan plane and round to oval in longitudinal scan planes; morphologically, glands comprised 2 lobes joined by an isthmus or a roughly diamond-shaped structure located on the ventral surface of the trachea. Major blood vessels and cervical lymph nodes were identified. Thyroid parenchyma was typically uniform and homogeneous, with echogenic reticulations and well-defined borders. Thyroid glands were hypoechoic or isoechoic relative to the sternocephalicus muscle; echogenicity was greater in adolescents than in adults. Thyroid gland volume differed between sexes, between sexually mature and immature dolphins, and among age groups and was positively correlated with body length and weight.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonography provided a reliable and repeatable method for evaluation of thyroid glands and adjacent anatomic structures in live dolphins.

Sonographic evaluation of thyroid morphology during the normal estrous cycle in the Indo-Pacific bottlenose dolphin (Tursiops aduncus)

Physiologic changes occurring in the thyroid in response to the estrous cycle have been noted in companion animals. However, in bottlenose dolphins, the influence of different reproductive states on thyroid morphology remains unclear. Sonography was used to evaluate the variations of thyroid morphology for nine consecutive estrous cycles of four sexually mature, female Indo-Pacific bottlenose dolphins (Tursiops aduncus). The estrous cycle was divided into two phases for evaluation: the follicular and luteal phases. To compare changes associated with sex, thyroid volumes were measured in the different phases during the estrous cycle of female dolphins and were compared to the ultrasound examinations of the four male dolphins measured over a 2-mo period. In males, there was no significant difference in thyroid volume during the study period (P > 0.05). The thyroid volume measured in combining all estrous cycle phases of the female dolphins was significantly larger than that measured in the male dolphins (P < 0.05). A difference in thyroid volume during the estrous cycle was observed, with the thyroid volume during the follicular phase significantly smaller (P < 0.05) than that of the luteal phase, and is possibly related to the influence of female sex steroids. Thyroid volume variability during estrus should, therefore, be taken into account when examining the thyroid gland of female dolphins.

Evaluation of two-dimensional and three-dimensional ultrasound in the assessment of thyroid volume of the Indo-Pacific bottlenose dolphin (Tursiops aduncus)

The assessment of thyroid volume plays an indispensable role in the diagnosis and management of different thyroid diseases. The present study evaluates the accuracy of dolphin thyroid volume measurement as determined by four two-dimensional (2D) ultrasound methods (A-D), with a standard of reference using three-dimensional (3D) ultrasound. The measurement accuracy for different recognized thyroid configuration is also evaluated. Inter- and intraoperator variability of the measurement methods was determined. Thyroid ultrasound examinations were conducted in 16 apparently healthy Indo-Pacific bottlenose dolphins (Tursiops aduncus) with 2D and 3D ultrasound under identical scanning conditions. All 2D ultrasound measurement methods yielded high accuracies (79.9-81.3%) when compared with the 3D ultrasound measurement, and had high measurement reproducibility (77.6-86.2%) and repeatability (78.1-99.7%). For 2D ultrasound measurements, Methods A and B were more accurate and reliable than Methods C and D, regardless of thyroid configuration. Ultrasound is useful in the measurement of thyroid volume in bottlenose dolphins. For the first time, a reliable ultrasound scanning protocol for measuring dolphin thyroid volume was developed, which provides a means to establish a normative reference for the diagnosis of thyroid pathologies and to monitor the thyroid volume during the course of treatment in living dolphins. Key words: 3D ultrasound, Indo-Pacific bottlenose dolphin, thyroid volume measurement, Tursiops aduncus.

A comparison of portable ultrasound and fully-equipped clinical ultrasound unit in the thyroid size measurement of the Indo-Pacific bottlenose dolphin

Measurement of thyroid size and volume is a useful clinical parameter in both human and veterinary medicine, particularly for diagnosing thyroid diseases and guiding corrective therapy. Procuring a fully-equipped clinical ultrasound unit (FCUS) may be difficult in most veterinary settings. The present study evaluated the inter-equipment variability in dolphin thyroid ultrasound measurements between a portable ultrasound unit (PUS) and a FCUS; for both units, repeatability was also assessed. Thyroid ultrasound examinations were performed on 15 apparently healthy bottlenose dolphins with both PUS and FCUS under identical scanning conditions. There was a high level of agreement between the two ultrasound units in dolphin thyroid measurements (ICC = 0.859-0.976). A high intra-operator repeatability in thyroid measurements was found (PUS: ICC = 0.854-0.984, FCUS: ICC = 0.709-0.954). As a conclusion, no substantial inter-equipment variability was found between PUS and FCUS in dolphin thyroid size measurements under identical scanning conditions, supporting further application of PUS for quantitative analyses of dolphin thyroid gland in both research and clinical practices at aquarium settings.

Canine hypothyroidism: a review of aetiology and diagnosis

Hypothyroidism is recognised as an important endocrine disorder of dogs, and a frequent differential for numerous presenting complaints. Its diagnosis has never been straight forward as results suggestive of hypothyroidism can occur for a variety of reasons in dogs with normal thyroid function (euthyroid). As a consequence, the accurate investigation of hypothyroidism has been hindered by the potential inclusion of a number of cases not truly hypothyroid. In recent years, the development of newer diagnostic tests, e.g. free thyroxine, canine thyroid stimulating hormone, thyroglobulin autoantibodies, has significantly improved our ability to reliably differentiate hypothyroidism from other clinically similar disorders. This has led to a marked increase in our knowledge of the phenotypic, genotypic and aetiological aspects of this disorder in dogs.

Pre- and post-treatment ultrasonography in hypothyroid dogs

Primary hypothyroidism is a frequent endocrine disorder in the adult dog. However, false-positive diagnoses are common because of the relatively low accuracy of most commonly used biochemical tests. The purpose of this study was to describe the ultrasonographic features of the thyroid gland in hypothyroid dogs, to calculate the diagnostic sensitivity of gray-scale ultrasound using a combination of clinical symptoms and biochemical thyroid tests as gold standard, and to investigate the evolution of the ultrasonographic features after treatment of hypothyroidism. Eighteen dogs were studied prospectively. All dogs underwent an ultrasound examination at first presentation and 13 underwent one or two additional ultrasound examinations over time. At first presentation, a sensitivity of 76.5% (95% CI [50.0-93.0% 1) for decreased echogenicity, 64.7% (95% CI [38.385.8% 1) for inhomogeneity, 70.6% (95% CI 144.0-89.7%]) for irregular capsule delineation, 64.7% (95% CI [38.3-85.8%]) for abnormal lobe shape and 47.1% (95% CI 123.0-72.2%]) for decreased relative thyroid volume was obtained. Combining these five parameters together resulted in an overall sensitivity of 94.1% (95% CI [71.3-99.9%]) for gray-scale ultrasound in the detection of acquired hypothyroidism at first presentation. A continuous decrease of thyroid volume was seen over time after treatment, while the other investigated parameters did not change significantly during the follow-up period. None of the thyroid glands were considered normal at the last presentation. Grayscale ultrasound is a sensitive and quick test for the diagnosis of primary hypothyroidism in dogs.