Operative failure in minimally invasive parathyroidectomy utilizing an intraoperative parathyroid hormone assay

Background: Minimally invasive parathyroidectomy (MIP) is a targeted operation to cure primary hyperparathyroidism utilizing intraoperative parathyroid hormone monitoring (IOPTH). The purpose of this study was to quantify the operative failure of MIP. Methods: Utilizing institutional parathyroid surgery database, demographic, operative, and biochemical data were analyzed for successful and failed MIP. Operative failure was defined as <6 months of eucalcemia after operation. Results: Five hundred thirty-eight patients (96.6 %) had successful MIP with mean follow-up of 13 months, and 19 (3.4 %) had operative failure. The major cause of operative failure (11 of 19) was the result of surgeons' inability to identify all abnormal parathyroid glands. The remaining eight operative failures were the result of falsely positive IOPTH results. Eleven of 19 patients whose MIP had failed underwent a second parathyroid surgery. All but one of these patients achieved operative success, and 9 patients had missed multigland disease. Only 46 (8.3 %) of 557 patients had conversion to bilateral cervical exploration (BCE). Eighty percent of patients had more than 70 % IOPTH decrease, and all had successful operations. Patients with a marginal IOPTH decrease (50-59 %) had a treatment failure rate of 20 %. Conclusions: The most common cause of operative failure in MIP utilizing IOPTH was the result of surgeons' failure to identify all abnormal parathyroid glands. Falsely positive IOPTH is rare, and a targeted MIP utilizing IOPTH can achieve an excellent operative success rate without routine BCE. Selective BCE on patients with marginal IOPTH decrease may improve surgical outcome.