Minimally invasive parathyroidectomy and preoperative MIBI scans: Correlation of gland weight and preoperative PTH

Background: Minimally invasive parathyroidectomy (MIP) has become increasingly popular for the treatment of patients with primary hyperparathyroidism (pHPT), and the specific techniques used vary from surgeon to surgeon. This strategy depends on preoperative localization tests, of which the MIBI scan is the most commonly used. This study details one surgeon's MIP experience and examines factors that correlate with the results of sestamibi (MIBI) scans. Study design: A retrospective review of parathyroidectomies performed between 1996-2006 was performed to create a database including laboratory and imaging results, symptoms, length of stay, and complications. MIBI scans were classified as correct when they showed one area of uptake at the site of a single adenoma (SA) found at exploration. Correlation between patient factors and MIBI scan results were assessed with Spearman correlation and Wilcoxon rank-sum tests. Results: Of 263 patients having parathyroidectomy for pHPT, 205 had SA, 40 double adenomas, 15 hyperplasia, and 3 negative explorations. Normocalcemia was achieved in 98% of patients at 1 year and 95% by intraoperative parathyroid hormone (PTH) criteria. Factors that were significantly correlated with MIBI scan results in SA patients were preoperative PTH (p = 0.0025) and adenoma weight (p < 0.0001). The median PTH in those with correct scans was 137 versus 101 pg/mL in those with incorrect scans, and the median adenoma weights were 920 and 280 mg, respectively. Conclusions: The MIBI scan is a good localization test that made unilateral exploration and MIP possible in 76% of the cases. MIBI scans are more likely to be correct with higher preoperative PTH and larger adenomas.