Primary hyperparathyroidism: Correlation between cervical ultrasound and MIBI scan.

Introduction: The standard gold treatment of primary hyperparathyroidism (PHP) is parathyroidectomy. Imaging in particular, cervical ultrasound (US) and technetium-99 m- méthoxyisobutylisonitrileparathyroid scintigraphy using the single-photon emission computed tomography (TC-99 m-MIBI-SPECT) are always indicated prior to parathyroid surgery, allowing the location of parathyroid adenomas. The objective of our study is to evaluate the contribution of TC-99 m-MIBI-SPECT and US in the preoperative topographic diagnosis of PHP. Materials and
Methods: this is a descriptive and analytical retrospective study, conducted in our department of Endocrinology, Diabetology and Metabolic Diseases in Hassan II University Hospital of Fez between 2009 and 2018. All patients who received a para-thyroidectomy for PHP were recruited. All patients had received a cervical US and a TC-99 m-MIBI-SPECT. We compared imaging data before surgery with data from intraoperative exploration and anatomopathological findings of surgical samples.
Results: Forty-eight patients were collected. US correctly identified parathyroid adenoma in 85.40% of patients with PHP versus 89.50% in TC-99 m-MIBI-SPECT. US correctly predicted surgical outecomes in 97.60% of patients and TC-99 m-MIBI-SPECT in 97.72% of cases. Their combination had better results in sensitivity and positive predictive value.
Conclusion: TC-99 m-MIBI-parathyroid scintigraphy SPECT had a higher probability for solitary parathyroid adenoma compared to cervical US. Its use coupled with the TC-99 m-MIBI-parathyroid scintigraphy SPECT allows reliable preoperative tracking.

INTRODUCTION

It was long considered a rare disease; primary hyperparathyroidism (PHP) is now a common disease.[1] The most common cause of PHP is an adenoma of one of the four parathyroid glands. Rarely, PHP is part of one of three forms of family PHP.[2] Parathyroid surgery has evolved significantly over the last 25 years. Most surgeons have rapidly accepted the use of minimally invasive surgery (MIP) instead of traditional parathyroidectomy. Indeed, MIP has a lot of advantages such as reducing operating time, length of hospitalization, and postoperative complications.[3] The location of the skin incision is usually dictated by preoperative tracking data. Imaging in particular ultrasound (US) and technetium-99 m-méthoxyisobutylisonitrileparathyroid (TC-99 m-MIBI)-parathyroid scintigraphy are indicated prior to parathyroid surgery, thus locating parathyroid adenomas. In recent years, single-photon emission computed tomography (SPECT)/CT has been added to parathyroid scintigraphy protocols to provide a valuable three-dimensional localization.[4] Their diagnostic accuracy was similar, if not superior, to those of second-line localization methods such as CT scans or magnetic resonance imaging.[5] While the cervical US provides more anatomical details; TC-99 m-MIBI-SPECT gives functional details. The purpose of our study is to assess the contribution of TC-99 m-MIBI-SPECT and cervical US for presurgical localization of abnormal parathyroid glands in patients with PHP while comparing imaging data with data from intraoperative exploration and anatomopathological findings.

MATERIALS AND METHODS

Patient selection

This retrospective study enrolled all patients who underwent a parathyroidectomy for PHP between 2009 and 2018 in the Department of Endocrinology, Diabetology and Metabolic Diseases of hospital university Hassan II de Fez. We included all symptomatic patients (bone pain or fracture, renal lithiases). Patients with asymptomatic PHP under surveillance only, PHP discovered during pregnancy were excluded. All of our patients had a biological assessment of calcemia, albuminemia, phosphoremia, daily urinary calcium excretion, parathyroid hormone (PTH), and 25 hydroxyl vitamin D. The PHP was diagnosed on the basis of the finding of high levels of total and/or ionized calcium and high or inappropriate PTH levels. All of our patients had a cervical US and TC-99 m-MIBI-parathyroid scintigraphy-SPECT.

The cervical US was performed at the radiology department by an expert radiologist in the parathyroid gland. The report provided specifies the following: seat, size, echogenicity, and vascularization.

The TC-99 m-MIBI-parathyroid scintigraphy was performed in the Nuclear medicine Department of Hospital University Hassan II Fez. Hybrid wash-out protocol (double tracer): acquisition of images on hybrid camera SPECT/CT Symbia T6.

Thyroid tracking scan

realization of a planar recording in previous incidence 10 min after injection of 49 MBq of Pertechnetate.

Parathyroidal scintigraphy

realization of a planar recording with an anterior incidence 10 min and then 2, 4, and 6 h after injection of 550 MBq of 99 mTc MIBI. Followed by a single-photon emission computed tomography (SPECT)/CT.

The scintigraphic and US results before surgery were compared with the results of intraoperative exploration and anatomopathological findings of surgical samples. The reference standard for correct localization was the location of the gland or glands on the basis of surgical reports, with pathologic confirmation of resected glands as parathyroid adenoma or hyperplasia.

Informed consent

All patients gave their verbal consent for use of their anonymized data for scientific purposes.

Statistical analysis

The statistical analysis was conducted using Microsoft Excel 2004 (XML) and EPI info 7(7.2.2. Février 2018). Quantitative values are expressed on average-standard deviation and qualitative values as a percentage. For all analyses, a P = 0.05 was considered to be significant.

RESULTS

Forty-eight patients were enrolled. The average age was 55.6 years with a female predominance. Demographic and biological characteristics are summarized in Table 1.

Table 1

Demographic and biological characteristics of our population

Parameters	Average
Age (years)	55.6 ±11.6
Female/male	4.3
Calcemia (mg/l)	113±0.6
Phosphoremia	28±0.1
Phosphatase alcaline (UI/L)	234±168
PTH (pg/ml)	534±394
Urinary calcium (mg/day)	611±214
Size of adenoma (cm)	3.4±2.4
PTH in postoperative (pg/ml)	56±14

PTH=Parathyroid hormon

Table 2 shows the following information.

Table 2

Positive and negative results by ultrasound and TC 99m MIBI SPECT

	True positive	True negative	False positive	False negative	Total	Sensitivity (%)	Specificity (%)	Accurancy (%)	PPV (%)
US	41	2	1	4	48	91.1	66.6	89.5	97.6
TC-99m-MIBI-SPECT	43	2	1	2	48	95.5	66.6	93.7	97.72
Combined US and TC-99m-MIBI-SPECT	45	1	0	2	48	95.7	100	95.8	100

US=Ultrasound, TC-99m-MIBI-SPECT=Technetium-99m-methoxyisobutylisonitrile-single photon emission computed tomography, PPV=Positive predictive value

Among the 48 patients, cervical US correctly identified 41/48 adenomas (85.40%) and TC-99 m-MIBI-SPECTidentified43/48 adenomas (89.50%). Furthermore, when both modalities were applied together, 45/48 (93.70%) adenomas were correctly detected.

Of the 48 suspected adenomas, the overall sensitivity of cervical US, TC-99 m-MIBI-SPECT, and the combined US and TC-99 m-MIBI-SPECT with respect to anatomopathological findings were 91.10%, 95.50s%, and 95.70% respectively. While the overall specificity was 66.6%, 66.6%, 100%, respectively. Positive predictive values (PPVs) of US and TC-99 m-MIBI-SPECT and the Combined US and TC-99 m-MIBI-SPECT were 97.60%, 97.72% and 100% respectively for parathyroid adenomas [Figures 1 and 2].

Figure 1

Cervical ultrasound showing a mass under and retro thyroid left lobar; measuring 2.30 cm in longitudinal section. In Color Doppler: central and peripheral hypervascularization of the parathyroid nodule

Figure 2

Cervical ultrasound showing a mass under and retro thyroid left lobar; measuring 2.30 cm in longitudinal section. In Color Doppler: central and peripheral hypervascularization of the parathyroid nodule

DISCUSSION

Prior to the advent of imaging, previous studies had objected that exploratory cervicotomia was curative in 92%–95% of cases.[5] Preoperative topographical imaging to locate the pathological gland in a preoperative setting is highly recommended. It will avoid surgical failures.[6] A variety of imaging techniques have been used in the past to provide presurgical localization for parathyroid surgery. Currently favored approaches use US and Tc-99 m-MIBI. They have benefited from technological advances. In addition; they provide the resolution and specificity that achieve the required PPVs.[5] The two techniques are complementary. This preoperative localization is essential if we are considering a MIP with a unilateral surgical approach under local anesthesia, which have tended to develop since the 1990s.[7] MIP can be done either through the standard Kocher incision, a smaller midline incision, with video assistance or through an ectopically placed, extracervical incision. Indeed, this technique compared to conventional surgery reduces the duration of surgery, the limitation of fibrosis-the area operated-if indication of a new re-intervention as well as the stay at the hospital.[8] In their study, Cakal et al.[9] had shown that cervical US had a sensitivity of 89.7% and the TC-99 m-MIBI of 71.8%, and their combined use had a sensitivity of 92.3%. On the other hand, EAG Ibrahim et al.[10] reported an estimated 97.2% sensitivity of cervical US and 92% TC-99 m-MIBI and that their combinations increase the sensitivity to 100%. They explained his findings, by the fact that they had few cases of parathyroid hyperplasia in their series and they excluded ectopic parathyroid adenomas, secondary hyperparathyroidism. In our study, cervical US had a sensitivity of 91.10% and TC-99 m-MIBI-SPECTof 95.50%, and that their combinations increase the sensitivity to 95.70%. We can explain that by the use of MIBI scan coupled with the SPECT/CT which provides a valuable three-dimensional localization. Tokman et al. concluded through their study that there is significant value in adding SPECT-CT to initial diagnostic imaging algorithms to localize a parathyroid adenoma preoperatively.[4] In a number of cases (10%–15%),[11] 4.16% in our study, TC-99 m-MIBI-SPECT shows no fixation on parathyroid adenoma, even when it is in a nonectopic and good-size position. This finding, while unusual should not lead to questioning the diagnosis of location made by the v, if it is sufficiently safe. Conversely, TC-99 m-MIBI-SPECT may show an obvious fixation image that does not correspond to US to any precise image of parathyroid. In our study, cervical US was negative in 8.33%. Therefore, the presence of a concomitant multinodular goiter can distract this research. In this case, repeat the US, focusing it on the suspect region; this often allows to find an anomaly that had gone unnoticed at the first US.[10] In their study, Cakal et al. reported that the diagnosis of a parathyroid adenoma was missed by cervical US in 25% of patients with thyroid pathology.[9] Most diagnostic studies reported the PPV of the test instead of specificity due to false-negative cases. In their meta-analysis, comparing 12 studies, Moghadam et al. concluded that there were no significant differences between the two methods in terms of sensitivity and specificity. There were overlaps in 99% confidence intervals. The characteristics of the two methods are also similar.[12] Zang et al. had objected that cervical US and MIBI scans are two complementary techniques that overcome the limitations inherent in each technique.[13] In our study, the PPVs of US and TC-99 m-MIBI-SPECT and the Combined US and TC-99 m-MIBI-SPECT were 97.60%, 97.72% and 100% respectively for parathyroid adenomas.

CONCLUSION

In our study, Tc-99 m-MIBI-SPECT had a higher sensitivity, accuracy, and PPV for solitary parathyroid adenoma compared to the cervical US. Its use coupled with the Tc-99 m-MIBI-SPECT allows reliable preoperative identification in case of agreement of the two methods on the uniqueness of the adenoma.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.