Parathyroid adenoma: accuracy of preoperative localization by high-resolution real-time sonography

Parathyroid sonography: imaging and intervention

This article reviews the role of high-resolution sonography as an imaging modality for the diagnosis and treatment of patients with parathyroid disease. Included is a discussion of sonographic anatomy and technique, disease processes of the parathyroid glands and their sonographic appearances, preoperative imaging, and the use of sonography as a guide for diagnostic and therapeutic intervention in parathyroid disease.

Color Doppler sonography in the detection of parathyroid adenomas

BACKGROUND

Various diagnostic modalities have been utilized to aid in the detection of abnormal parathyroid tissue; however, its localization is not always easy. The purpose of this study was to determine whether the evaluation of potential hemodynamic changes in thyroid arteries could aid in the detection of parathyroid adenomas.

METHODS

Twenty-eight patients with laboratory evidence of hyperparathyroidism were examined with color Doppler sonography. Data were collected for the superior and inferior thyroid arteries separately. These findings were compared with data for a control group of 14 healthy subjects.

RESULTS

Retrospective analysis of the data indicated that peak systolic velocities in the inferior thyroid arteries ipsilateral with the parathyroid adenomas were significantly higher than in normal controls (p <.001). Peak velocity values in the superior thyroid arteries ipsilateral with parathyroid adenomas located in the upper position were also significantly increased compared with those in control subjects (p <. 02). Conversely, peak velocities in the inferior and superior thyroid arteries contralateral with the adenomas, as well as velocities in the superior thyroid arteries ipsilateral with lower position adenomas, did not differ significantly from those in control subjects. The localization of both side and level site of the adenomas presented an accuracy of 86.6%, sensitivity reached 96. 5%, and specificity 83.1%.

CONCLUSION

Our results suggest that color Doppler sonography can be used to improve diagnostic accuracy in detecting parathyroid adenomas.

Parathyroid Update: A Review of 220 Cases

A total of 220 patients have undergone cervical exploration for hyperparathyroidism by the author. A review of 125 cases was published in 1991. An additional 95 patients have been explored in the subsequent four years. Subtotal parathyroidectomy was performed in 39 patients with chronic renal failure. Exploration was successful in over 97% of the 181 patients diagnosed with primary hyperparathyroidism. Single adenomas were found in 146, double adenomas in 11, and multiple gland hyperplasia in 19 patients. Two of the five patients in whom cervical exploration failed were ultimately diagnosed with benign familial hypocalciuric hypercalcemia. Twenty-four adenomas were ectopic. Preoperative thallium-technetium scans and ultrasound correctly localized only 61% of the adenomas. Technetium sestamibi scans were correct in two of four adenomas. Only 47% of ectopic adenomas were correctly localized by isotope scanning and 29% by ultrasound.

All four glands should be examined at initial exploration. Because of the occurrence of double adenomas, contralateral exploration is always indicated regardless of whether an enlarged gland and a normal one are found on the first side. All enlarged parathyroids should be removed when dealing with single or multiple adenomas; subtotal parathyroidectomy (3-1/2 glands) should be performed in multiple gland hyperplasia. Frozen section confirmation of excised parathyroid tissue is essential. If exploration is unsuccessful, ectopic locations, such as the retroesophageal areas, thymus, anterior and posterior mediastinum, carotid sheath and thyroid lobe, must be examined carefully.

Preoperative localization studies are not as reliable as an experienced parathyroid surgeon.

Pre-operative localisation in primary hyperparathyroidism

One hundred and seventy-three patients operated on for primary hyperparathyroidism over a four year period by one experienced surgeon are reviewed. An overall success rate of 98.8% was achieved with information from pre-operative localisation using ultrasound and parathyroid venography with sampling. Parathyroid ultrasound was heavily dependent on the experience of the operator. An experienced ultrasonologist detected 63% of solitary adenomas and correctly localised the site of 82%. Glands were not detected if they were of small size or in an inaccessible site. He identified all those enlarged glands over 0.36 grams in weight that were lying in the usual site. In contrast, inexperienced ultrasonologists had a detection rate of 20%. Parathyroid venography with sampling detected a single site of excess hormone production in the neck of 79% of patients with a single adenoma, and correctly localised the site in 75% of these. The side was correctly predicted for 63% of glands, the level was correctly predicted for 56% and both side and level localisations were correct in 44%. Multi-gland disease was correctly suggested by the experienced ultrasonologist in 56% of cases and by parathyroid venography with sampling in 31% cases.

A potential new radiopharmaceutical for parathyroid imaging: radiolabeled parathyroid-specific monoclonal antibody--II. Comparison of 125I- and 111In-labeled antibodies

The biodistributions of 111In-BB5-G1 and 111In-F(ab')2 were compared with the biodistributions of the corresponding 125I-labeled molecules. For BB5-G1 intact antibody, the relative uptake of the 111In- and 125I-labeled molecules in human parathyroid tissue implants was similar at 24 h, but by 96 h the uptake of the 111In-BB5-G1 %ID/g was four times greater than that observed with the 125I-labeled antibody. For the F(ab')2 fragments, the relative parathyroid uptake of the two preparations was similar at all times tested. The uptake by the clearance organs was significantly higher when the 111In-labeled molecules were used. Imaging results suggest that 111In-BB5-G1 or 111In-F(ab')2 may be a useful radiopharmaceutical for parathyroid radioimmunodetection.

Parathyroid sonography: diagnostic accuracy related to shape, location, and texture of the gland

The sonographic features of 51 pathological parathyroid glands detected pre-operatively were analysed. Atypical texture was found in 23.5% and variation in shape in 15.6% of the cases. Cystic parathyroid glands are difficult to differentiate from thyroid cysts, and may be the cause of false positive diagnosis, as in three cases in this series. Topographic assessment showed a relatively low sensitivity in detecting disease in the right upper gland (50%) and in the upper mediastinum (70%). The decreased accuracy in these regions is probably because of the particular anatomical location of the right upper gland and sonographic limitations in screening the mediastinal region. Awareness by the radiologist and surgeon of the variations in texture and location may influence both diagnosis and intraoperative detection of the abnormal parathyroid gland.

Technetium-thallium scintiscanning for localization of parathyroid adenomas and hyperplasia. A reappraisal

The dual tracer nuclear scintiscan using technetium and thallium to localize enlarged or ectopic parathyroid tissue has been reported to be highly accurate and efficacious. Fourteen previous series reporting results of the technique have been compiled from the literature and analyzed. This analysis has revealed a total of 317 surgically confirmed scan results with a low false-positive rate (17 of 317 scans), a sensitivity rate of 82 percent, and an overall accuracy rate of 78 percent. Forty-five patients from five Portland area hospitals have been retrospectively studied. They had a total of 49 preoperative scans. In our experience with the scan, a higher false-positive rate (4 of 45 scans), a sensitivity rate of 78 percent, and an overall accuracy rate of 73 percent were noted. The scan's effectiveness in acknowledged areas of difficulty in parathyroid surgery, such as patients with ectopic adenomas, hyperplastic glands, and those with previous neck explorations, has been analyzed. We conclude that the scan is a useful preoperative localization tool, especially in patients with ectopic adenomas or with persistent hypercalcemia after neck exploration. However, it is less accurate than initially reported in complex patients, and additional localization techniques are frequently required.

Fine-needle biopsy of parathyroid adenomas

High-resolution real-time sonography was performed in 15 cases of clinically and chemically suspected primary hyperparathyroidism and in 20 patients with different thyroid nodules. The suspected enlarged parathyroid glands and the thyroid nodules were percutaneously punctured under sonographic control. Concentrations of parathyroid hormone, human thyroglobulin, and human calcitonin were measured in the aspirate, and immunocytology was performed. The mean concentration of the aspirated parathyroid hormone in the parathyroid glands was 4,013.6 pmol/l +/- 4,519 (SD) as compared with 14.9 pmol/l +/- 8.7 in the thyroid nodules. Thyroglobulin was present in the aspirated fluid of parathyroid adenomas located behind the thyroid (mean +/- SD, 398.1 ng/ml +/- 317). In comparison, the aspirated thyroglobulin from the thyroid nodules averaged 9,689.7 ng/ml +/- 3,732. Immunocytology for parathyroid hormone was positive in 14 of the 15 biopsied specimens. Of 15 patients who were scanned for suspected hyperparathyroidism, six had concomitant thyroid nodules. It is concluded that the measurement of high concentrations of parathyroid hormone in the aspirate from a cervical mass, with sonographic control of needle position and/or positive immunocytology provides absolute localization of parathyroid tissue.

Pre-operative localization of parathyroid tumours using static b scan ultrasonography

Time consuming, inaccurate and often invasive localization procedures before initial surgery in primary hyperparathyroidism are probably not justified. The clinical value of pulsed ultrasound has been appreciated since 1975 and the application of dedicated, high resolution, real time systems is now advocated. This paper examines the efficacy of conventional static B scan equipment in pre-operative localization of parathyroid tumours in 34 patients. When considering all glands, a true positive value (sensitivity) of 55.5 per cent was achieved, with a true negative rate (specificity) of 96.0 per cent. The accuracy for all glands (the true positive plus true negative results as a percentage of all glands scanned) was 85.3 per cent. An accuracy of 93 per cent was achieved when considering glands greater than 5 mm diameter, with false positive and negative rates of 3.6 and 20.0 per cent respectively. The limitations of the the technique are discussed in the context of the current literature.

High-resolution real-time sonography. The study of superficial body parts

High-resolution real-time scanning such as described in this article remains limited to the very superficial areas of the body. This article has been designed to give the reader an up-to-date glimpse of the minute world of small parts scanning and aid the clinician in the optimal use of this noninvasive modality.

Ultrasonic appearance of adenomatous and hyperplastic parathyroid glands

An investigation was made of the sonographic and histopathologic characteristics of 27 parathyroid adenomas and 11 primary and secondary hyperplastic parathyroid glands demonstrated by ultrasound before surgical confirmation. All the hyperplastic glands and 21 of the adenomas had a homogeneously sonolucent interior structure and a smooth periphery. The adenomas and hyperplastic glands were sonographically indistinguishable except for 5 large adenomas which had areas of varying echodensity and an irregularly nodulated periphery. The ultrasonically inhomogeneous adenomas were histopathologically more heterogeneous with asymmetric, nodular enlargement. One patient had a cystic adenoma. The results are discussed in relation to the ultrasonic appearance of thyroid noduli and lymph nodes being the main source of errors in parathyroid ultrasonography.

High-resolution parathyroid ultrasonography in familial benign hypercalcemia (familial hypocalciuric hypercalcemia)

Familial benign hypercalcemia, or familial hypocalciuric hypercalcemia (FHH), is frequently confused with primary hyperparathyroidism, but the consistent failure of subtotal parathyroidectomy to normalize serum calcium levels in FHH makes accurate distinction from familial hyperparathyroidism imperative. Because ultrasonography frequently demonstrates enlargement of the parathyroid glands in hyperparathyroidism, we examined 14 hypercalcemic adults (who had not undergone operation) from seven kindreds with FHH by using a high-resolution real-time scanner. We compared our results with those from 156 patients (who had undergone scanning preoperatively) with surgically confirmed hyperparathyroidism. Enlargement of the parathyroid glands was detected ultrasonographically in 137 of 156 (88%) of the total group of patients with hyperparathyroidism and in 17 of 24 patients (71%) with hyperparathyroidism who had hypercalcemia (serum calcium, 10.6 to 11.0 mg/dl) comparable to that of the FHH group (mean value, 10.7 mg/dl). In contrast, the single possible parathyroid lesion seen in the FHH group was substantially smaller (4 mm) than the smallest (7 mm, 75 mg) abnormal gland reliably detected by ultrasonography in the group with hyperparathyroidism and was conceivably normal in size. Patients with FHH have a dramatic absence of ultrasonographic parathyroid enlargement. High-resolution parathyroid ultrasonography may be of ancillary diagnostic benefit in patients with familial hypercalcemia.

Ultrasonic parathyroid localisation in previously operated patients

Sixty-two patients with hyperparathyroidism and failed prior neck surgery were examined by ultrasound before reoperation to localise abnormally enlarged glands. If mediastinal lesions are excluded, a total of 57 glands greater than 5 mm in size were removed from 48 patients. Ultrasound demonstrated only 18 of these for a true positive rate of 32%. There were 39/57 (68%) false negatives. In addition, there were 16 false positives. In our experience, the detection rate of ultrasound for enlarged parathyroid glands in patients with failed surgery is significantly less than that reported in previously unoperated patients (73%), or in the limited number of reported cases of patients with previous operations (75%). Our high false negative rate is probably partially due to the large number of posteriorly located small glands which cannot be adequately visualised by ultrasound. Nevertheless, because of its non-invasive nature, low cost and ready availability, ultrasound should be utilised as an initial screening procedure in patients with failed previous surgery.

Preoperative ultrasonographic diagnosis of a parathyroid adenoma in a child

The case of a young boy with primary hyperparathyroidism due to an adenoma is reported. The tumor was localized by ultrasonography, and a close correlation between the image and the surgical findings was found. Since primary hyperparathyroidism in children under 15 years of age is frequently due to adenomata larger than 1.5 cm it is suggested that ultrasonography of the neck should be included in the work-up of every children suspected to have this pathology.

Location of parathyroid adenomas by thallium-201 and technetium-99m subtraction scanning

Solitary parathyroid adenomas were correctly located before surgery in 20 out of 21 cases by using 201mT1 and 99mTc in a subtraction technique. The technique was not useful in identifying hyperplastic parathyroid glands. The technique is recommended as a useful procedure before surgery for primary hyperparathyroidism.

Impact of sonography on surgery for primary hyperparathyroidism

The impact of preoperative sonographic localization of enlarged parathyroid glands was evaluated from the standpoint of operative time and complication rates. There was a reduction in the average time from 135 minutes when findings were false-negative to 111 minutes when findings were positive. The rate of complication was not changed by accurate preoperative localization. When the operative goal is to find all parathyroid glands in every patient, the value of preoperative localization of parathyroid tumors by any current method is slight. Should operative policy favor a search for only one enlarged and one normal gland, or should methods improve to the point that even normal parathyroid glands can be located reliably, noninvasive localization should prove to be useful, safe, and cost-effective, even when it is carried out before initial operation.