Primary hyperparathyroidism: current strategies for imaging, surgery and follow-up

Abstract

Since the introduction of minimally invasive parathyroidectomy (MIP) twenty years ago, the focused approach has gradually replaced conventional neck exploration (CNE) as the routine procedure for primary hyperparathyroidism (pHPT). In this thesis, patients treated for pHPT, preferably by MIP, were evaluated to address several issues regarding the preoperative work-up, operative treatment and follow-up. MIP is only possible when a solitary adenoma is identified by preoperative imaging. Which imaging strategy is the most effective remains a matter of debate. In our opinion, the imaging algorithm of choice combines MIBI and US or MIBI and SPECT. Our data show that pushing the limits by the stepwise use of readily available imaging techniques increases the identification rate of solitary adenomas and select more patients for MIP. In case of negative preoperative MIBI and US one can both argue to perform additional imaging or proceed to a CNE. Intraoperative PTH assessment (IOPTH) is considered an important adjunct for successful MIP. However, IOPTH only confirms the successful removal of the adenoma and by no means helps the surgeon to find the correct location. Although helpful in selected cases, we plea against the routine use of IOPTH, since the attributive value seems marginal. Operative success is based on sustained normal calcium levels. While persistent hypercalcemia and recurrence are well described, the postoperative calcium drop has been poorly documented. We assessed the postoperative decline and concluded that measuring serum calcium on the day of, or the day after, surgery, does not contribute to the early prediction of operative success. The shift to MIP results in a higher frequency of solitary adenomas. In our cohort the frequency of solitary adenomas was 91%, while parathyroid hyperplasia was seen in less than 1%. The frequency of solitary adenomas was even higher when more imaging modalities were used as part of the preoperative work-up. Since it is unreliable to distinguish adenoma from hyperplasia, it seems conceivable that more glands were historically resected than necessary. While a straightforward work-up and operative approach is suitable for patients with non-familial pHPT, several subgroups require a tailored approach, such as patients on lithium, MEN-patients and recurrence due to parathyromatosis. A significantly higher prevalence of hypercalcemia was found in bipolar patients on lithium. The observed incidence argues for regular serum calciummeasurements in these patients. MEN2A patients are similar to pHPT with respect to their operative approach; a focused minimally invasive parathyroidectomy may be advocated for both. In MEN1 patients however, the percentage of multiglandular disease and recurrence rates are as high as 54%. We advocate treating these patients with a CNE and subtotal parathyroidectomy. One of the more rare causes of recurrent elevated serum calcium levels is parathyromatosis, which is thought to be the result of intraoperative “spilling” of parathyroid tissue. Emphasis should be placed on removing abnormal glands in one piece. Knowledge of the existence of parathyromatosis is crucial for every (para)thyroidsurgeon