To observe the distribution characteristics of ectopic parathyroid glands and explore the difference of ^99mTc-MIBI SPECT/CT and ultrasonography in the detection of ectopic parathyroid glands.

A retrospective review was performed on patients with secondary hyperparathyroidism in the outpatient or inpatient department of China-Japan Friendship Hospital from July 2013 to July 2018. Of 358 patients who underwent ^99mTc-MIBI SPECT/CT and ultrasound examinations, 38 had ectopic parathyroid glands. The clinical data of the patients were collected to analyze the distribution characteristics of ectopic parathyroid glands and compare the detection of ectopic parathyroid glands by ^99mTc-MIBI SPECT/CT and ultrasound.

Among the 358 patients, 38 cases of ectopic parathyroid glands were detected, with a detection rate of 10.61%. The distribution of ectopic parathyroid glands is as follows: the anterior mediastinum and thymus (25, 65.8%), the lower inferior lobe of the thyroid gland (2, 5.3%), the posterior cricoid cartilage (1, 2.6%), the lateral middle lobe of the thyroid gland (1, 2.6%), the supraclavicular fossa (1, 2.6%), the carotid sheath (1, 2.6%), the posterior superior sternocleidomastoid (1, 2.6%), the submandibular gland (1, 2.6%), the piriform fossa (1, 2.6%), the greater horn of the hyoid bone (1, 2.6%), the tracheoesophageal sulcus (2, 5.3%), the lateral central thyroid gland (1, 2.6%), and the subclavian artery (1, 2.6%). For the 38 cases of ectopic parathyroid glands found by SPECT/CT, only 13 (34.2%) were found by ultrasound, of which 4 (16.0%) were located in the anterior mediastinum and thymus (4/25, 16.0%) and 9 (69.2%) were located in other sites, suggesting that the efficiency of ultrasonography in the detection of ectopic parathyroid glands in deeper locations (anterior mediastinum and thymic gland) was low. The 38 patients underwent a total of 60 surgical operations (including 46 cases of general surgery, 7 cases of thoracoscopic surgery, and 7 cases of ultrasonic-guided microwave thermal ablation), and there were 10 patients who did not remove their ectopic parathyroid glands and needed to be operated again. All the unremoved parathyroid glands were ectopic in the thorax.

The high incidence of ectopic parathyroid is still the main reason for the failure of parathyroid gland surgery. ^99mTc-MIBI SPECT/CT is an ideal examination method for finding ectopic parathyroid glands. For the detection of mediastinal or thymic ectopic parathyroid glands, ^99mTc-MIBI SPECT/CT is superior to ultrasound.