Ultrasonographic features of normal parathyroid glands confirmed during thyroid surgery in adult patients
Article information
Abstract
Purpose
This study was performed to examine the ultrasonography (US) features of normal parathyroid glands (PTGs) that were identified on preoperative US and subsequently confirmed during thyroid surgery.
Methods
This retrospective study included a consecutive sample of 161 patients (mean±standard deviation age, 56±14 years; 128 women) with 294 normal PTGs identified on preoperative US PTG mapping and confirmed during thyroidectomy. A presumed normal PTG on US was defined as a small, round to oval, hyperechoic structure in the central neck. These presumed normal PTGs, as identified on preoperative US, were mapped onto thyroid computed tomography images and diagrams of the thyroid gland and neck. During the preoperative real-time US examinations, the location, size, shape, echogenicity, echotexture, and intraglandular vascular flow of the identified presumed PTGs were assessed. These characteristics were compared between superior and inferior PTGs using the generalized estimating equation method.
Results
The typical US features of homogeneous hyperechogenicity without intraglandular vascular flow were observed in 267 (90.8%) normal PTGs, while atypical features, including isoechogenicity (1.0%), heterogeneous echotexture with focal hypoechogenicity (5.8%), and intraglandular vascular flow (3.7%), were noted in 27 (9.2%). Inferior PTGs were more frequently identified in posterolateral (36.1% vs. 5.3%) and thyroid pole locations (29.9% vs. 5.3%), and less frequently in posteromedial locations (29.2% vs. 88.0%), compared to superior PTGs (P<0.001 for each comparison).
Conclusion
Most normal PTGs displayed the typical US features of homogeneous hyperechogenicity without intraglandular vascular flow. However, in rare cases, normal PTGs exhibited atypical features, including isoechogenicity, heterogeneous echotexture with focal hypoechogenicity, and intraglandular vascular flow.
Introduction
Ultrasonography (US) is a primary diagnostic tool for evaluating parathyroid disease [1,2]. According to the longstanding consensus, normal parathyroid glands (PTGs) are typically not visible and are difficult to reliably identify on US [3-7]. However, advancements in US imaging technology have led to several recent studies [8-12] demonstrating that normal PTGs can indeed be identified. Research has suggested that the echogenicity of normal PTGs varies, ranging from hypoechoic [13,14] to isoechoic or hyperechoic [15,16]. A study by Xia et al. [9] indicated that 91% of the 23 intraoperatively identified normal PTGs exhibited homogeneous hyperechogenicity compared to neck muscle during intraoperative US examination. Similarly, Cohen et al. [10] reported homogeneous hyperechogenicity in six normal PTGs confirmed by tissue-washout parathyroid hormone or autofluorescence. Kim et al. [11] observed that 10 normal PTGs, confirmed by tissue-washout parathyroid hormone, were hyperechoic relative to the thyroid gland and could be reliably differentiated from metastatic lymph nodes in patients with thyroid cancer. The preoperative localization of presumed normal PTGs through US evaluation has recently gained recognition for its potential clinical importance in patients undergoing thyroidectomy [8,12].
Nevertheless, the US characteristics of normal PTGs, as confirmed by biochemical tests or intraoperative findings, have been described in a limited number of reports and are not yet well established. This study aimed to investigate the US features of normal PTGs that were identified preoperatively and confirmed intraoperatively during thyroid surgery in a large cohort of consecutive adult patients.
Materials and Methods
Compliance with Ethical Standards
This single-institution, observational, retrospective, cross-sectional study received approval from the relevant institutional review board (2022-06-002). Informed consent was waived due to the retrospective nature of the study.
Study Participants
From August 2021 to November 2022, this study enrolled 161 consecutive patients (mean±standard deviation age, 56±14 years; 128 women) with 294 normal PTGs (150 superior and 144 inferior) identified on preoperative US PTG mapping and confirmed during thyroidectomy. The inclusion criteria for this study were as follows: (1) adult patients (≥19 years), (2) undergoing initial hemithyroidectomy or total thyroidectomy for thyroid disease following preoperative US PTG mapping, and (3) with presumed normal PTGs identified on preoperative US and confirmed as normal PTGs during thyroid surgery. The exclusion criteria were as follows: (1) patients with abnormal preoperative serum calcium levels, (2) those for whom presumed normal PTGs were not identified on preoperative US PTG mapping, and (3) those for whom any presumed normal PTG identified on preoperative US was not confirmed as a normal PTG during thyroid surgery.
A normal PTG was determined when the presumed normal PTG identified on preoperative US was confirmed during thyroid surgery based on reference standards.
These reference standards included intraoperative findings (confirmation as a normal PTG by the surgeon during thyroid surgery) and a biochemical criterion (a normal serum calcium level). Of 211 consecutive patients who underwent thyroid surgery during the study period, the followings were excluded: patients with a history of prior hemithyroidectomy (n=3), individuals undergoing thyroid surgery other than hemithyroidectomy or total thyroidectomy (n=5), patients who did not undergo preoperative US PTG mapping (n=8), those with abnormal preoperative serum calcium levels (n=2), those in whom presumed normal PTGs were not identified on preoperative US PTG mapping (n=7), and those in whom any presumed normal PTG identified on preoperative US was not confirmed as normal PTG during thyroid surgery (n=25) (Fig. 1). Of 476 presumed normal PTGs identified on preoperative US among the 161 included patients, 294 were confirmed as normal PTGs during thyroidectomy and included in the analysis, after excluding 182 unconfirmed presumed PTGs (no surgical exploration [n=118] and no intraoperative identification after surgical exploration [n=64]) (Fig. 1).
Flow diagram of patient enrollment.
PTG, parathyroid gland; US, ultrasonography.
Preoperative US Identification and Assessment of US Features of Normal PTGs
All preoperative evaluations of normal PTGs using US were performed with a 5-12 MHz linear-array transducer (EPIQ7, Philips Healthcare, Bothell, WA, USA) by an experienced radiologist (D.G.N.) with 23 years of expertise in thyroid and neck US imaging and intervention. A structure that appeared small (approximately 3-15 mm in long diameter and 2-5 mm in short diameter), round to oval, and hyperechoic in the central neck on both transverse and longitudinal US images was defined as presumed normal PTG, as supported by the literature [9-11] (Fig. 2). If a presumed normal PTG exhibited mixed echogenicity, the predominant echogenicity was used for its classification. Hyperechogenicity was defined as a greater echogenicity than that of the normal thyroid gland. For superior PTGs located deep in the neck, isoechogenicity with the normal thyroid gland was deemed acceptable for defining a presumed normal PTG.
A 59-year-old woman with a follicular adenoma and occult follicular variant papillary carcinomas (infiltrative subtype) in the right thyroid lobe.
A. Transverse ultrasonography (US) without probe compression shows the right superior normal parathyroid gland (PTG) in the tracheoesophageal groove with poor delineation. B. A longitudinal US without probe compression displays an ill-defined, isoechoic PTG (arrows). A, B. Transverse and longitudinal US, obtained using real-time dynamic assessment with neck compression by the US probe, clearly reveal a small (3×5 mm), ovoid, hyperechoic normal superior PTG (arrows) in the right posteromedial perithyroidal region, adjacent to the tracheoesophageal groove near the cricoid cartilage. C. An intraoperative surgical field photograph shows the normal superior PTG (arrows) in the right superior thyroid bed, corresponding to the preoperatively identified location of the normal superior PTG on US. RL, right thyroid lobe.
The optimized US imaging technique for identifying presumed normal PTGs, particularly superior PTGs, involved real-time dynamic assessment. This technique entailed gradually compressing the neck with the US probe to improve the detection of deeply situated PTGs by reducing US beam attenuation, while evaluating the anatomical relationship of the surrounding thyroid tissue in real time during the US examination [17]. The echogenicity of the presumed normal PTGs was assessed using US images captured while applying neck compression. The details of the US imaging technique for identifying normal PTGs are described in Supplementary Text 1 and depicted in Fig. 2 and Video clip 1.
The location and US characteristics—including size, shape, echogenicity, echotexture, and intraglandular vascular flow—of presumed normal PTGs were evaluated by an experienced radiologist (D.G.N.) during real-time US examination for preoperative PTG mapping. Presumed normal PTGs situated at or above the midpoint of the thyroid gland were classified as superior PTGs, while those below the midpoint were classified as inferior [18-20]. Presumed normal PTGs were further categorized into orthotopic and ectopic PTGs; the latter were defined as those located more than 3 mm from the edge of the thyroid poles on the longitudinal US image. The relationship of orthotopic presumed normal PTGs to the thyroid gland was categorized on US images as posterior, anterior, or at the thyroid pole. The posterior or anterior perithyroidal locations were further divided into medial and lateral, based on the centerline of both thyroid lobes on the transverse US image. PTGs were identified as being at the superior or inferior thyroid pole when the center of the PTG was outside the thyroid gland, but the margin of the PTG was within 3 mm of the edge of the thyroid poles on the longitudinal US image. The size of normal PTGs was estimated by measuring the long and short diameters. The shape was assessed using the ratio of the long diameter to the short diameter (hereafter termed the L/S ratio) and categorized as round (ratio 1-1.5), ovoid (ratio 1.6-3.0), or elongated (ratio >3). The echogenicity of presumed normal PTGs was classified as either hyperechoic (more echogenic than the normal thyroid gland) or isoechoic (similar echogenicity to the normal thyroid gland). The echotexture was categorized as homogeneous (uniform echogenicity) or heterogeneous (mixed echogenicity with focal hypoechoic areas). The presence or absence of intraglandular vascular flow was assessed using conventional color Doppler US, with parameters optimized for detecting slow flow velocity. Interobserver agreement for the US features of normal PTGs was assessed between one observer (D.G.N.), who performed the real-time US assessment, and another (W.P.), with 7 years of experience in thyroid and neck US imaging, who conducted a retrospective assessment of the US images. The second observer (W.P.) independently reviewed static US images, blinded to the results of the US features assessed during the real-time US examination.
Preoperative US PTG Mapping and Intraoperative Confirmation of Normal PTGs
Preoperative US PTG mapping consisted of two main steps: initially, the identification and localization of presumed normal PTGs using US, and subsequently, the anatomical localization of these identified PTGs on thyroid computed tomography (CT) images and a diagram of the thyroid gland and neck. For PTG mapping, the anatomical locations of presumed normal PTGs detected on US were marked on thyroid CT images acquired with a specialized thyroid CT protocol for thyroid cancer (Supplementary Text 2) [21], as well as on a diagram of the thyroid gland and neck. This process utilized anatomical landmarks of the thyroid gland and surrounding structures, such as vessels, that were visible on both US and CT images. A comprehensive report of the mapped CT images and diagram was then uploaded to the picture archiving and communication system for use as a reference during surgery (Fig. 3, Supplementary Fig. 1).
A 58-year-old woman with papillary thyroid carcinoma (PTC) in the left thyroid lobe.
A. Transverse and longitudinal ultrasonography (US) reveal a small (4×7 mm) ovoid, hyperechoic, normal superior parathyroid gland (PTG) (arrows) in the right posteromedial perithyroidal region. B. US display a small (3×6 mm) ovoid, hyperechoic, ectopic superior PTG (arrows) in the left upper central neck, positioned 7 mm above the upper margin (arrowheads) of the left upper thyroid pole. C, D. US demonstrate ovoid, hyperechoic, normal inferior PTGs at the right lower thyroid pole (4×10 mm) (arrows) (C) and left lower thyroid pole (3×5 mm) (arrows) (D).
Normal PTGs were identified by the surgeon through visual inspection in the surgical field. If confidence was low regarding visual recognition of a normal PTG, or if metastatic lymph nodes or other pathological conditions were suspected, a frozen section biopsy was conducted before autotransplantation of the PTGs. The intraoperative locations of normal PTGs were categorized according to three sites—superior, inferior orthotopic, and inferior ectopic—on each side of the neck. The agreement between these intraoperative findings and the preoperative US PTG mapping was recorded on a predefined surgical record sheet after thyroidectomy.
Statistical Analysis
Categorical variables are reported as frequencies and percentages within each category. Continuous variables are presented as either the median with interquartile range (for variables with a nonparametric distribution) or the mean±standard deviation (for those with a parametric distribution). The US features of normal PTGs were compared between superior and inferior PTGs using the generalized estimating equation method to account for within-patient correlation, as many patients had multiple PTGs. The associations of atypical US features with patient factors (age, sex, and body mass index [BMI]) and the characteristics of normal PTGs, including location, size, and shape (L/S ratio), were evaluated. The chi-square test was used for sex; the Mann-Whitney U test for size, L/S ratio, and BMI; and the Student t-test for age. The agreement rate and interobserver agreement regarding the US features of normal PTGs between the two observers (D.G.N. and W.P.) were calculated using the Cohen kappa (κ) statistic. The κ values were interpreted as follows: 0 to 0.20 indicated slight agreement; 0.21 to 0.40, fair; 0.41 to 0.60, moderate; 0.61 to 0.80, substantial; and 0.81 to 1.0, almost perfect agreement [22]. Statistical analyses were performed using SPSS version 28.0 for Windows (IBM Corp., Armonk, NY, USA) and SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). A P-value of less than 0.05 was considered to indicate a statistically significant difference.
Results
Patient Characteristics
The baseline characteristics of the 161 patients are summarized in Table 1. Total thyroidectomy was performed for 97 (60.2%) patients, while hemithyroidectomy (lobectomy) was performed for 64 (39.8%). The final diagnoses included thyroid neoplasms in 146 patients (90.7%)—with 31 benign tumors, 15 low-risk neoplasms, and 100 malignant tumors—and non-neoplastic diseases in 15 patients (9.3%)—comprising 12 cases of nodular hyperplasia and three cases of diffuse thyroid disease.
Demographic and clinical characteristics of patients
Anatomic Distribution of Normal PTGs Included in the Study
Of the 294 confirmed normal PTGs identified during thyroidectomy, 150 (51.0%) were superior and 144 (49.0%) were inferior (Table 2). Most glands were orthotopic (97.3%, 286/294) and situated in the posterior perithyroidal region (81.8%, 234/286). Most superior PTGs were in the posteromedial perithyroidal region (88.0%, 132/150), with smaller numbers found in the posterolateral region (5.3%, 8/150), at the upper thyroid pole region (5.3%, 8/150), and in ectopic locations (0.7%, 1/150). The distribution of inferior PTGs was more varied: 29.2% (42/144) in the posteromedial, 36.1% (52/144) in the posterolateral, and 29.9% (43/144) in the lower thyroid pole regions, and 4.9% in ectopic locations (7/144). Compared to superior PTGs, inferior PTGs were more commonly found in the posterolateral (36.1% vs. 5.3%, P<0.001), thyroid pole (29.9% vs. 5.3%, P<0.001), and ectopic locations (4.9% vs. 0.7%, P=0.061), with a lower incidence in the posteromedial location (29.2% vs. 88.0%, P<0.001) (Figs. 3, 4).
Anatomic distribution of normal PTGs included in the study (n=294)
A 50-year-old woman with papillary carcinoma in the right thyroid lobe.
A. Transverse and longitudinal ultrasonography (US) reveal a small (2×4 mm) ovoid, hyperechoic, normal superior parathyroid gland (PTG) (arrows), situated in the left posteromedial perithyroidal region adjacent to the margin of the pharyngoesophageal junction. B. US display a small (2×8 mm) elongated, hyperechoic, ectopic inferior PTG (arrows) in the left lower central neck, positioned 17 mm inferior to the lower margin (arrowheads) of the left lower thyroid pole.
US Features of Normal PTGs
The US characteristics of the 294 normal PTGs are detailed in Table 3. The median long diameter was 6.0 mm (range, 3 to 14 mm), and the median short diameter was 3 mm (range, 2 to 5 mm). The median L/S ratio was 2.3 (range, 1.0 to 4.5). Regarding shape, the PTGs were ovoid in 234 cases (79.6%), elongated in 32 cases (10.9%), and round in 28 cases (9.5%). A total of 291 PTGs (99.0%) were hyperechoic, with three superior PTGs (1.0%) displaying isoechogenicity (Supplementary Fig. 2). A homogeneous echotexture was observed in 277 PTGs (94.2%), while 17 PTGs (5.8%) exhibited heterogeneous echogenicity with focal intraglandular hypoechogenicity (nodular in 12, linear in four, and irregular in two) (Figs. 5, 6). Intraglandular vascular flow was absent in 283 PTGs (96.3%) and present in 11 PTGs (3.7%) on conventional color Doppler US (Figs. 5, 6). The typical presentation was homogeneous hyperechogenicity without intraglandular vascular flow, found in 267 PTGs (90.8%). Atypical features, including isoechogenicity, heterogeneous echotexture with focal hypoechogenicity, and intraglandular vascular flow, were observed in 27 PTGs (9.2%) from 23 patients. No significant relationship was observed of atypical US features with clinical factors such as age (P=0.938), sex (P=0.576), and BMI (P=0.528), nor with the characteristics of normal PTGs, including location (P=0.928), size (long diameter, P=0.599; short diameter, P=0.096), and shape (P=0.121).
Ultrasound features of normal PTGs (n=294)
A 75-year-old woman with follicular adenoma and occult papillary carcinoma in the right thyroid lobe.
A. Transverse and longitudinal ultrasonography (US) reveal a small (4×8 mm), ovoid, hyperechoic normal superior parathyroid gland (PTG) with a tiny, nodular, hypoechoic lesion (indicated by arrows) in the right posteromedial perithyroidal region. B. Conventional color Doppler US demonstrate an absence of vascular flow within the right superior PTG.
A 53-year-old woman with papillary carcinoma in the left thyroid lobe.
A. Transverse and longitudinal ultrasonography (US) reveal a small (3×6 mm) ovoid, hyperechoic, normal-appearing superior parathyroid gland (PTG) with a tiny nodular hypoechoic lesion (arrowhead) and a linear, slightly hypoechoic lesion (arrows) in the left posteromedial perithyroidal region. B. A conventional color Doppler US displays prominent intraglandular vascular flow (arrows) within the left superior PTG.
The median long diameter of normal inferior PTGs was slightly greater than that of normal superior PTGs (median, 6.5 mm vs. 6 mm; P=0.024). However, no significant differences were observed in the short diameter, the L/S ratio, or other US features between normal superior and inferior PTGs (P≥0.098).
Interobserver Agreement on US Features of Normal PTGs
Regarding interobserver agreement, the results indicated fair agreement for echogenicity (κ=0.28; 95% confidence interval [CI], -0.16 to 0.72; agreement rate, 98.3%), substantial agreement for echotexture (κ=0.70; 95% CI, 0.53 to 0.87; agreement rate, 96.3%), and almost perfect agreement for intraglandular vascular flow (κ=0.87; 95% CI, 0.74 to 1.0; agreement rate, 99.0%).
Discussion
In this study, which included 294 intraoperatively confirmed normal PTGs, typical US characteristics were observed in 90.8% of cases. These characteristics included an ovoid shape (varying from round to elongated), homogeneous hyperechogenicity, and an absence of intraglandular vascular flow. However, atypical features such as isoechogenicity in superior PTGs, heterogeneous echotexture with focal hypoechogenicity, and intraglandular vascularity were infrequently observed, occurring in 9.2% of the glands.
This study supports findings from several previous reports on the US characteristics of normal PTGs as diagnosed by biochemical methods [10,11], intraoperative US [9], and US of surgical specimens [23]. However, these earlier studies were based on a very limited number of confirmed normal PTGs. The present research represents the first investigation to identify both typical and atypical US features of normal PTGs, confirmed using the reference standards of intraoperative findings and a biochemical criterion (normal serum calcium levels), in a large cohort of consecutive adult patients undergoing thyroid surgery.
The anatomical distribution of the included normal PTGs was consistent with the known distribution of normal superior and inferior PTGs. The inferior PTGs exhibited a more variable distribution and were often found in ectopic locations below the lower pole of the thyroid along the thyrothymic ligament [18-20]. The atypical US features of isoechogenicity, heterogeneous echotexture with focal hypoechogenicity, and intraglandular vascular flow align with findings reported previously [9,11]. The typical hyperechogenicity of normal PTGs is attributed to the abundant stromal fat content, which is diffusely distributed in the gland, resulting in increased echogenicity of the glandular tissue. This phenomenon is due to the heterogeneous glandular architecture, which contains numerous interfaces, as opposed to the hypoechogenicity of typical parathyroid adenomas that have a homogeneous architecture due to the cellular proliferation of chief cells [24,25]. However, three normal superior PTGs in this study displayed isoechogenicity to the normal thyroid gland. This could have been due to the deep location of superior PTGs, where US beam attenuation was not adequately reduced by probe compression, or it could be attributed to the intrinsic wide variation in stromal fat content within normal PTGs [24]. The focal intraglandular hypoechogenicity exhibited variable shapes on US, including nodular, linear, and irregular forms. The histopathologic identity of this US finding remains uncertain; however, it may be associated with incidental tiny parathyroid cysts or neoplasms [11,26], prominent intraglandular vessels, or an uneven distribution of fat tissue within the normal PTG [24]. Notably, the residual hyperechoic area of normal PTGs with focal intraglandular hypoechogenicity consistently demonstrated the same homogeneous hyperechogenicity as that observed in other typical normal PTGs. The absence of intraglandular flow signals in normal PTGs, except in rare cases with prominent intraglandular vessels, is likely due to the low sensitivity of conventional color Doppler US imaging to the slow flow of microvessels within the normal PTGs. Consequently, the US features of intraglandular flow signals in normal PTGs may differ when slow flow imaging techniques, such as microvascular flow or superb microvascular imaging, are utilized.
The real-time dynamic assessment technique involving US probe compression offers two key advantages. First, it minimizes US beam attenuation, which improves the assessment of echogenicity in deeply situated PTGs. Second, it can help determine whether a PTG is distinct from surrounding tissues during dynamic evaluation, which aids in the localization of normal PTGs. The present study demonstrated a higher detection rate of normal PTGs per patient and a lower rate of isoechoic normal PTGs compared with recent studies investigating presumed normal PTGs [27,28]. These findings suggest that the dynamic assessment technique may be more effective in identifying normal PTGs and assessing their echogenicity. Accurate localization of normal PTGs via US has substantial clinical implications, particularly in the assessment of thyroid and parathyroid diseases. Preoperative localization can improve the intraoperative identification of normal PTGs in patients undergoing thyroidectomy, potentially preventing their accidental removal and reducing the risk of postoperative hypoparathyroidism [8,12]. Additionally, the hyperechoic US feature of normal PTGs enables reliable distinction from hypoechoic or isoechoic metastatic lymph nodes due to thyroid cancer [11], hypoechoic parathyroid neoplasms or hyperplasias [25], and isoechoic ectopic thyroid tissues or thyrothymic thyroid rests around the lower thyroid pole [29]. In this study, 64 PTGs identified and presumed normal on preoperative US were not confirmed by surgical exploration. Potential reasons include the inability to detect existing normal PTGs during surgery due to their deep location, interference from coexisting multiple metastatic lymph nodes in some cases, and potential false positive results of presumed normal PTGs on US. However, the likelihood of false positives was minimized because the analysis included only normal PTGs confirmed during surgery.
This study has several limitations. First, the normal PTGs identified on US were not directly verified by histopathological or biochemical methods. However, the surgeon did assess the intraoperative matching of PTGs identified on US with reference to the preoperative US PTG mapping summary report for all patients. Second, the study did not evaluate the accuracy of US in identifying normal PTGs. Future research should investigate both false positive and false negative identifications of normal PTGs. Third, the reference standard for normal PTGs in this study does not rule out the inclusion of normocalcemic primary hyperparathyroidism or pathologic PTGs of normal size with non-functioning tiny microadenomas. Fourth, only one experienced radiologist assessed the US features of normal PTGs during real-time US examination. The interobserver agreement on the US features of normal PTGs assessed by two observers using different methods (real-time vs. static images) may differ from the result of interobserver agreement by two observers using the same real-time US assessment. The degree of interobserver agreement for echogenicity was only fair (κ=0.28, agreement rate 98%), which may be due to slight differences in echogenicity between isoechogenicity and hyperechogenicity. However, the low κ value, despite the high agreement rate (98.3%) for the echogenicity of the normal PTG, may be explained by the kappa paradox due to the very low prevalence of isoechogenicity and the imbalanced marginals of the data [30,31]. Fifth, this study involved only one type of high-resolution US machine from a single institution. Further investigation with various US machines from multiple institutions is necessary to validate the results.
In conclusion, most of the normal PTGs displayed the typical US characteristics of homogeneous hyperechogenicity without intraglandular vascular flow. However, normal PTGs infrequently presented atypical US features, such as isoechogenicity, heterogeneous echotexture with focal hypoechogenicity, and intraglandular vascular flow. The accurate identification of these US characteristics of normal PTGs is crucial for distinguishing them from perithyroidal lesions and facilitates the preoperative localization of normal glands prior to thyroidectomy in adult patients.
Notes
Author Contributions
Conceptualization: Na DG. Data acquisition: Na DG. Lee JC, Song YJ, Yoon K, Noh BJ. Data analysis or interpretation: Kim SJ, Paik W, Na DG. Drafting of the manuscript: Kim SJ, Paik W, Na DG. Critical revision of the manuscript: Lee JC, Song YJ, Yoon K, Noh BJ, Na DG. Approval of the final version of the manuscript: all authors.
No potential conflict of interest relevant to this article was reported.
Acknowledgements
This study was supported by the Medical Research Promotion Program, administered through Gangneung Asan Hospital and funded by the Asan Foundation (2022II0011).
Supplementary Material
Supplementary Fig. 1.
A summary report of the preoperative ultrasonography parathyroid gland mapping with mapped computed tomography images and a diagram (case of Fig. 3) (https://doi.org/10.14366/usg.24104).
Supplementary Fig. 2.
Images in a 36-year-old female with papillary carcinomas in both thyroid lobes (https://doi.org/10.14366/usg.24104).
Supplementary Text 1.
Ultrasonography (US) imaging techniques for identifying normal parathyroid glands (PTGs) (https://doi.org/10.14366/usg.24104).
Supplementary Text 2.
Thyroid computed tomography (CT) protocol and image acquisition parameters (https://doi.org/10.14366/usg.24104).
Video clip 1.
Dynamic assessment ultrasonography (US) video demonstrating the visualization of the right normal superior parathyroid gland through gradual compression of the neck using the US probe (case of Fig. 2) (https://doi.org/10.14366/usg.24104).
References
Article information Continued
Notes
Key point
The typical ultrasonography (US) features of homogeneous hyperechogenicity without vascular flow were observed in 90.8% of normal parathyroid glands (PTGs). Atypical features such as isoechogenicity, heterogeneous echotexture, and vascular flow were observed in 9.2% of normal PTGs. Accurate identification of the US features of normal PTGs can assist in distinguishing them from other perithyroidal lesions and facilitates the preoperative localization of normal glands.