Factors in conversion from minimally invasive parathyroidectomy to bilateral parathyroid exploration for primary hyperparathyroidism

Background: Ongoing experience has documented equivalence of minimally invasive parathyroidectomy (MIP) and standard bilateral parathyroid exploration (BPE) for primary hyperparathyroidism in most patients; however, intraoperative conversion of MIP to BPE is required for multiple indications. This study analyzes the factors, predictors, and cure rates in converted MIP. Methods: We retrospectively analyzed a database of 1,002 patients undergoing initial parathyroidectomy for primary hyperparathyroidism from 2008 to 2011 for rate of successful MIP, converted MIP, planned BPE, and factors leading to conversion from MIP to BPE. Results: Of 989 included parathyroidectomies, 647 (65%) were successful MIP, 186 (19%) were converted MIP, and 156 (16%) were planned BPE. The most common indication for conversion included intraoperative parathyroid hormone (IOPTH) criteria not met (46%), localization incorrect (36%), and evidence of multigland disease (17%). Converted MIP had lower preoperative calcium and PTH and lower baseline IOPTH compared with successful MIP. Complication rates were similar; however, rates of persistent hyperparathyroidism were highest in converted MIPs (6%) versus planned BPEs (3%) and successful MIPs (2%; P <.01). Conclusion: Patients requiring conversion of MIP to BPE have lower preoperative serum calcium and PTH levels, a less dramatic decrease in IOPTH, and a greater rate of persistent disease than successful MIP.