In patients who are referred for surgical management of primary hyperparathyroidism, a successful outcome may be defined as identification and removal of the adenoma with a commensurate drop in post-operative PTH and serum calcium levels. The traditional operation for primary parathyroid disease is a four-gland exploration via a bilateral neck exploration (BNE).  This operation is performed through a large neck incision and puts vital structures in both sides of the neck (recurrent laryngeal nerves and normal parathyroid glands) at risk.

Over the last decade, minimally-invasive parathyroidectomy (MIP) has evolved as the preferred operation in the hands of surgeons with dedicated expertise in the thyroid and parathyroid disease.  MIP is performed through a small incision on an outpatient basis with shorter anesthesia.  The surgeon places the scar over the suspected quadrant of the adenoma. Surgical risks to other structures in the neck are mitigated by the narrow and directed anatomic scope of the surgery. Successful removal of the adenoma is confirmed intraoperatively by frozen section or by a decrease in serum parathyroid hormone level.

The success of MIP is dependent on reliable pre-operative localization of the adenoma. For more than two decades, the gold-standard imaging study for the identification of an adenoma was nuclear scintigraphy (SestaMibi). There is a wide variability in the reported sensitivity and specificity of SestaMibi in the setting of primary hyperparathyroidism.  Many surgeons will also refer a patient for neck ultrasonography by the radiology department before surgery.  The results of radiologist-performed ultrasound (RUS) and the SestaMibi are then synthesized by the surgeon to create an operative plan.

A recent development in the practice of many Head and Neck Endocrine Surgeons is office-based surgeon-performed ultrasound (SPU).  SPU is emerging as an invaluable tool in the workup, diagnosis, treatment, and follow-up of a variety of diseases of the thyroid, parathyroid, and neck. For patients with a parathyroid adenoma, a head and neck endocrine surgeon with formal training in neck ultrasonography is ideally suited to participate in the pre-operative localization workup.

The surgeon may apply his or her practical knowledge of surgical anatomy and parathyroid location (and variability) to the task of ultrasound localization.  This differs from the role of the radiologist who has access to only limited aspects of the clinical history and is responsible for reporting the imaging findings in the context of a wide differential diagnosis. Because the successful outcome of parathyroidectomy depends on the surgeon, his or her motivation to apply the ultrasound for pre-operative localization may differ from those of the radiologist. Studies comparing SPU and RUS in primary hyperparathyroidism suggest that SPU may be more sensitive that RUS (82-83% sensitivity versus 42-82%, respectively). 1,2

SPU may also be more sensitive than SestaMibi in the workup of primary hyperparathyroidism. Steward et al. compared SPU to SestaMibi in 103 patients undergoing parathyroid surgery.  SPU was found to be significantly more sensitive than SestaMibi in predicting the correct quadrant of the adenoma (87% versus 58%; p<0.001). 3

These findings have led some head and neck endocrine surgeons to propose a new imaging (localization) algorithm for the workup of patients with primary hyperparathyroidism. In this algorithm, patients are referred for surgical consultation and SPU first.  If SPU identifies a candidate adenoma, MIP is performed.  In cases where the SPU is equivocal or negative in identifying the adenoma, a SestaMibi is ordered. 4

There are, however, certain limitations to SPU.  The success of SPU is operator-dependent. SPU will likely achieve sensitivities comparable or better than RUS or Sestamibi if it is performed by a dedicated thyroid/parathyroid surgeon who regularly performs office-based ultrasound of the neck. Certain neck conditions may also decrease the sensitivity of SPU, including obesity, multi-nodular goiter, thyroiditis and neck adenopathy. Furthermore, SPU is not well-suited as the sole localization study in patients with ectopic parathyroid glands.

In summary, the judicious use of SPU in the pre-operative localization of a parathyroid adenoma may obviate the routine use of other imaging modalities such as RUS and SestaMibi in some patients.  The routine use of SPU as a sensitive localization modality for primary hyperparathyroidism may also decrease the number of patients who undergo bilateral neck explorations due to equivocal, negative, or contradictory results from traditional localization studies such as SestaMibi and radiologist-performed ultrasound. Improvements in pre-operative localization such as SPU may ultimately increase the number of patients who are candidates for MIP.

References

1.  Soon PS, Delbridge LW, Sywak MS, Barraclough BM, Edhouse P, Sidhu SB. Surgeon performed ultrasound facilitates minimally invasive parathyroidectomy by the focused lateral mini-incision approach.  World J Surg. 2008 May;32(5):766-71.  (web link)

2.  Van Husen R, Kim LT. Accuracy of surgeon-performed ultrasound in parathyroid localization. World J Surg. 2004 Nov;28(11):1122-6.  (web link)

3.  Steward DL, Danielson GP, Afman CE, Welge JA.  Parathyroid adenoma localization: surgeon-performed ultrasound versus sestamibi.  Laryngoscope. 2006 Aug;116(8):1380-4.  (web link)

4.  Surgeon-performed ultrasound: a single institution experience in parathyroid localization.  Jabiev AA, Lew JI, Solorzano CC. Surgery. 2009 Oct;146(4):569-75; discussion 575-7.  (web link)