What is the recommended imaging approach for localizing parathyroid adenomas or hyperplasia in patients with primary hyperparathyroidism?

Parathyroid Imaging for Hyperparathyroidism

Initial Imaging Approach

For primary hyperparathyroidism requiring surgery, begin with either ultrasound combined with 99mTc-sestamibi scintigraphy (preferably with SPECT/CT), or proceed directly to 18F-choline PET/CT as first-line localization studies. 1

Key Principle: Imaging Role

• Imaging localizes abnormal parathyroid glands to facilitate minimally invasive parathyroidectomy (MIP); it has no utility in confirming or excluding the diagnosis of hyperparathyroidism, which is established biochemically. 1

First-Line Imaging Options

Combined Ultrasound and Nuclear Medicine

• Ultrasound combined with 99mTc-sestamibi scintigraphy (dual isotope with planar and SPECT/CT acquisitions) provides high sensitivity and specificity when used together, superior to either modality alone. 2, 3
• Ultrasound alone achieves 87% overall diagnostic accuracy and 96% detection rate for single adenomas, making it the most cost-effective initial study. 4
• 99mTc-sestamibi demonstrates 81% sensitivity for adenomas and 100% for hyperplasia. 5

18F-Choline PET/CT

• 18F-choline PET/CT demonstrates superior diagnostic performance for identifying parathyroid hyperplasia and multiple adenomas compared to traditional scintigraphy. 3
• This modality is particularly valuable for multigland disease, which affects 15-20% of primary hyperparathyroidism patients. 1, 3

Clinical Context Determines Strategy

Single Adenoma (80% of Cases)

• Most patients have a single parathyroid adenoma and are candidates for MIP, which requires confident preoperative localization. 1
• MIP offers shorter operating times, faster recovery, and decreased perioperative costs compared to bilateral neck exploration. 1

Multigland Disease Suspicion

• When multigland disease is suspected (hereditary syndromes, multiple endocrine neoplasia, or biochemical patterns suggesting hyperplasia), no single imaging modality is sufficient. 4
• Combination of ultrasound, CT, and additional studies alerts clinicians to multiple gland involvement in 87% of cases. 4

Second-Line Imaging for Negative or Equivocal Results

If Initial Studies Are Negative

• Perform 18F-choline PET/CT if the initial examination was sestamibi scintigraphy. 2
• 4D-CT parathyroid scan (multiphase CT with noncontrast, arterial, and venous phases) has sensitivities ranging from 62-88% and is particularly valuable for ectopic adenomas in the root of the neck. 1, 6, 4
• MRI achieves 94% detection rate and serves as an excellent confirmatory test. 4

Advanced Techniques for Persistent Negative Imaging

• Selective venous sampling for PTH levels may be considered for surgical candidates with non-localizing results, with sensitivities ranging from 40-93%, though this is invasive and typically reserved for reoperative cases. 6
• Fine-needle aspiration cytology with PTH determination in flushing fluid is possible after multidisciplinary discussion in expert centers. 2

Special Clinical Scenarios

Reoperative Hyperparathyroidism

• Preoperative imaging is essential in persistent (failure to achieve normocalcemia within 6 months) or recurrent (hypercalcemia after ≥6 months normocalcemia) hyperparathyroidism. 1
• Reoperations have lower cure rates and higher complication rates than first-time surgery, making accurate localization critical. 1

Concurrent Thyroid Disease

• In patients with equivocal findings and concurrent thyroid nodular disease, 18F-choline PET/MRI and 4D-CT help better characterize lesions. 3

Secondary/Tertiary Hyperparathyroidism

• For medically refractory secondary or tertiary hyperparathyroidism (typically multigland disease), imaging aims to identify all eutopic, ectopic, and supernumerary glands. 1
• Parathyroidectomy should be considered for tertiary hyperparathyroidism despite negative imaging. 6

Negative Imaging

• When preoperative localization studies are negative, bilateral neck exploration under general anesthesia remains the standard approach, allowing identification of all parathyroid glands. 6

Common Pitfalls to Avoid

• Failing to consider multigland disease, which is more difficult to localize with standard imaging, can lead to inadequate treatment. 6
• Do not use imaging to diagnose hyperparathyroidism—diagnosis is biochemical (elevated serum calcium and PTH). 1
• Intraoperative gamma probe detection alone (50% sensitivity for adenomas) is less accurate than preoperative sestamibi imaging and should not replace comprehensive preoperative localization. 5

Algorithm Selection Considerations

The selection of initial imaging should consider surgeon and radiologist preference, regional expertise, and patient-specific factors including suspicion for multigland disease, hereditary causes, and concomitant thyroid disease. 1 Multiple imaging modalities may be utilized in combination during initial evaluation to maximize accuracy through concordant results. 1