Diffuse thyroid disease in the pediatric population can lead to gross metabolic abnormalities affecting development and growth rendering early accurate diagnosis mandatory [7]. Traditionally the diagnosis is achieved by clinical examination, thyroid hormones levels, and thyroid ultrasonography [8]. Thyroid ultrasound is pivotal to the assessment of the gland’s echogenicity, volume, and vasculature as well as any related or surrounding abnormality [9]. SWE is a recent ultra-sound-based elastography method with the ability to quantitatively evaluate thyroid gland stiffness using the concept of strain elastography [10]. Any diffuse thyroid disease with its disease-related histological changes, e.g., follicular cell hyperplasia, lymphocytic infiltration, and colloid accumulation will change the glandular elastic properties, and if these histological changes proceed for a longer time, fibrosis, septations, and focal nodularity may evolve [11].
In the present study, we attempted to perform conventional thyroid Ultrasound to patients with autoimmune thyroiditis and normal participants calculating the gland’s volume and examining its parenchyma for echogenicity, the extent of heterogeneity, and pseudo-nodular appearance. Regarding the volume of the thyroid gland, we observed patients with AIT had significantly higher total thyroid volume (10.88 ml; IQR 0.6–22.47 ml) than control subjects (5 ml; IQR 2.87–7.87 ml). This matched the results of a previous retrospective study done by Kandemirli et al. [12] whose study population’s total thyroid volume with AIT was significantly higher than that of the healthy control group (HT group:9.73 ml; IQR 5.31–16.73 ml, control subjects: 4.11 ml; IQR 2.42–5.72 ml).
Ultrasonography is a widely used imaging tool in the diagnosis and follow-up of AIT. Its reported common findings of glandular heterogeneity, hypoechogenicity, and lobulated outline though specific are hardly sensitive [13]. The AIT disease-related histological changes including lymphocytic infiltration and interstitial fibrosis [14] consequently lead to parenchymal stiffness when compared to healthy thyroid tissue which will be invariably reflected in elasticity values [15]. In our study, elasticity mean values are higher in patients with autoimmune thyroiditis as compared to normal subjects in the same age group. Our reported mean elasticity value of the healthy control group was 9.35 ± 1.63 kPa (5.7–13.21 kPa) and the AIT group was 35.63 ± 20.30 kPa (8.43–103.7 kPa) which was close to the elasticity values of Kara et al. [16] who studied 149 participants ranging from 8 to 60 years showing the result of mean elasticity value in patient with AIT to be 25.01 ± 10.53 kPa (10.72–68.27 kPa). The elasticity values were also close to many other studies [17,18,19,20,21].
Kandemirli et al. [12] studied 59 patients diagnosed with HT and 26 healthy volunteers without any thyroid-related disorders, they used a scoring system based on gray-scale ultrasonographic findings subdividing patients with Hashimoto thyroiditis into three categories as follows: focal thyroiditis (grade 1), diffuse thyroiditis (grade2), and fibrotic thyroid gland (grade 3). Based on elasticity values, grade 3 patients had the highest and the most significant elasticity values (19.7 kPa; IQR 17.8–21.5 kPa) when compared to the patients with grade 2 (15.5 kPa; IQR 14.5–17.8 kPa) and grade 1 thyroiditis (12.8 kPa; IQR 11.9–13.1 kPa). Vlad et al. [21] also studied 104 patients the mean elasticity value in patients with AIT was found to be 26.2 ± 10.8 kPa with SWEmax 52.4 ± 24.6Kpa. In our study, the SWE of thyroid gland in children with AIT was found to be 35.63 ± 20.3; IQR 8.43–103.7 kPa which is consistent with the values of Ruchala et al. [17] which had reported having baseline thyroid stiffness in chronic autoimmune thyroiditis(CAT) to be 36.15 ± 18.7 kPa.
In healthy children our mean SWE was found to be 9.35 ± 1.63 kPa; IQR 5.73–13.21 kPa which is the approximate SWE postulated by Bhatia et al. [22] (9.0 ± 4.0 kPa).
In the study conducted by Kandemirli et al. [12] they reported no significant correlation between SWE and TGOAb in patients with HT. Our study also showed a negative correlation between SWE, TPOAb and TGAb. In concordance with Kara et al. [16], our study showed no positive correlation between SWE and TFT(TSH & T4) as well.
The cutoff value of elasticity in our study was 12.317 kPa with sensitivity, specificity, and accuracy rates of 96.9%, 100% and 98%, respectively. The cutoff value with the highest diagnostic accuracy for elasticity value in the study conducted by Fukuhara [19] was 12.3 kPa with reported sensitivity, specificity, and accuracy rates of 87.4%, 78.7% and 85.1%, respectively.
In our study, we were dependent on clinical examination, ultrasound findings, and laboratory tests, to diagnose AIT rather than tissue biopsy which we consider a limitation, this being rather controversial as any fine needle biopsy or surgery would have altered the gland parenchyma. In addition, most of our patients were under medication with Eltroxin and some of them were on the carbimazole medication. We considered this irrelevant guided by previous studies which reported no significant elasticity changes when comparing treated and non-treated patients [18, 23]. We also ignored age-related changes having a rather narrow age group; this was decided upon because previous studies documented statistically insignificant changes with narrow age gaps [24].
Conclusions
SWE is a useful and highly sensitive imaging method that complements routine ultrasonography examination in children with autoimmune thyroid disease by providing objective numerical values and estimating the degree of fibrosis. However, further studies are recommended to seek out the conventional reference values per age groups in the pediatric population. Larger cohorts in the Egyptian population are needed to compare the elasticity values of normal and pathologic tissues.
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