Primary hyperparathyroidism: how not to miss parathyroid tumors

The 4-dimensional CT scan (4dCT) is very useful in localizing parathyroid tumors prior to surgery. However its true precision is unknown. Parathyroid masses can produce excessive PTH leading to hypercalcemia, hypophosphatemia, osteoporosis, kidney stones and vascular calcifications. Appropriate identification and resection of adenomas is thus imperative.

Study discovers that 4dCT is inaccurate in about 30% of the cases, primarily due to the following clinical and anatomical reasons: presence of multiglandular hyperparathyroidism (or 7.6), an inferiorly located parathyroid adenoma (or 6.8), a small parathyroid mass <1.0 cm (or 4.4), and existence of confounding thyroid nodules (or 1.8).

These findings would be important to an endocrine surgeon performing parathyroidectomies, as it changes intraoperative expectations and intervention.

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JAMA Surgery

Prospective

August 2017

Importance: Parathyroid 4-dimensional computed tomographic scans (4D-CTs) have emerged as an accurate and cost-effective initial localization study for patients with primary hyperparathyroidism. However, potential limitations and factors affecting the accuracy of preoperative 4D-CTs remain poorly defined.

Objectives: To characterize factors associated with missed parathyroid lesions on preoperative 4D-CTs and to investigate patterns of commonly observed errors.

Design, Setting, and Participants: A prospectively accrued patient database was analyzed from September 1, 2011, through October 31, 2016. The study was performed in a tertiary referral center. Consecutive patients with primary hyperparathyroidism undergoing preoperative 4D-CTs and subsequent parathyroidectomy were included in the study.

Main Outcomes and Measures: 

Discordance between preoperative 4D-CTs and intraoperative findings in the number and location of abnormal parathyroid lesions.

Results: 

Of 411 patients studied (mean age 59 years; 79.1% female), 123 (29.9%) had discordance between preoperative 4D-CTs and intraoperative findings. Among the 411 patients, 75 (18.2%) had major discordance, including:

Incorrectly localized adenoma on the contralateral side of the neck, missed double adenoma, and absence of any abnormal lesion detected on 4D-CTs.

Compared with concordant cases, discordant cases had higher frequencies of multigland disease (66.7 vs 24.3%, p < .001) and multinodular goiter or thyroid nodule (40.7 vs 29.2%, p = .02).

Missed parathyroid lesions were smaller (mean 0.86 vs 1.24 cm; p < .001) and were more likely to be in the inferior position (65.4 vs 38.1%, p < .001).

Independently associated with discordant 4D-CT results.

Multigland disease (OR, 7.63, p<0.05),

Parathyroid lesion in the inferior position (OR, 6.82, p<0.05),

Parathyroid lesion size <1.0 cm (OR 4.37, p<0.05).

Multinodular goiter or thyroid nodule (OR, 1.82, p<0.05), 

Conclusions and Relevance:

Multigland disease was most strongly associated with discordance between preoperative 4D-CTs and intraoperative findings, followed by parathyroid lesion in the inferior position and parathyroid lesion size of 10 mm or less.

Awareness of these potential pitfalls may allow surgeons to better leverage this new localization technique in preoperative planning and intraoperative troubleshooting.