Anatomical distribution and number of parathyroid glands, and parathyroid function, after total parathyroidectomy and bilateral cervical thymectomy

Abstract

The normal distribution of parathyroid glands is well documented. However, this study aims to evaluate the efficacy of total parathyroidectomy (TPTx) and bilateral cervical thymectomy (BCTx) for the treatment of secondary hyperparathyroidism (SHPT) through identifying the location of parathyroid glands with attention to the pattern and frequency of orthotopic and ectopic glands.Between 2013 and 2018, sixty chronic hemodialysis patients with medically refractory SHPT underwent TPTx & BCTx. The adequacy of the operation was defined by the pathological confirmation of at least 4 parathyroid glands, accompanied by an intact parathormone (iPTH) value of <60 pg/mL on postoperative day 1(POD1). Based on their anatomical localizations, four distinct sites were identified for both the upper (Zone I-IV) and lower parathyroid glands (Zone V-VIII).The mean follow-up was 15.2 ± 14.6 months. The mean iPTH values on POD1 were normal in 50 patients, with an average of 11.7 ± 14.4 pg/mL. Ten patients (16.6%) had persistent HPT after the operation, three of whom underwent complementary parathyroidectomy. The surgical success rates after first and second operations were both 83.3%. A total of 235 parathyroid glands were detected. Ninety-two percent of the upper parathyroids were located in Zones I and II. However, almost 28% of the lower parathyroids were ectopic and located in Zones VII and VIII.At least one fourth of the lower parathyroids are ectopic; for this reason, Zones VII and VIII require careful investigation during surgery. For upper parathyroids not found in Zone I-III, total thyroidectomy on the same side is recommended.

Figure 1

Anatomical sites of superior parathyroid glands. Delineation of sites as follows: Zone I: the area at the posterior aspect of the thyroid between the cricothyroid ligament and the anatomic demarcation of the recurrent laryngeal nerve and inferior thyroid artery, Zone II: the area below the position where the inferior thyroid artery enters the thyroid and crosses the inferior laryngeal nerve, Zone III: cranially and along the posterior aspect of the superior thyroid artery, Zone IV: intrathyroidal.

Figure 2

Anatomical sites of inferior parathyroid glands. Delineation of sites as follows: Zone V: at the posterior aspect of the thyroid and between the junctions of the inferior thyroid artery/the thyroid gland and the inferior thyroid vein/the thyroid gland, Zone VI: within 1.0–1.5 cm. caudally from the point where the inferior thyroid vein enters the thyroid gland, Zone VII: along the thyrothymic ligament, Zone VIII: between the carotis sheath and esophagus below the lower pole of the thyroid.