Addressing the challenges of missed parathyroid glands in ultrasonography for secondary hyperparathyroidism: a retrospective observational study

Abstract

Purpose: Preoperative localization plays an important role in secondary hyperparathyroidism (SHPT) surgery. The advantages of neck ultrasound (US) include high availability and low cost. However, the reported sensitivity of US is 54%-76%, and the reason for missed parathyroid glands (PGs) on US has been rarely addressed.

Methods: Fifty-four patients who were diagnosed with renal SHPT from September 2020 to March 2022 were included in this retrospective study. Preoperative localization included surgeon-oriented US and technetium 99m-sestamibi single-photon emission CT (SPECT)/CT.

Results: A total of 212 PGs were pathologically confirmed, resulting in a success rate of 96.2% (52 of 54). Using echo, 193 PGs (91.0%) were accurately localized, while 19 glands (9.0%) were not identified, including those in ectopic positions (n = 12, at thymus or intrathyroid or others), of small size (<1 cm, n = 6), or overlapping with an ipsilateral PG (n = 1). US accurately detected 4 PGs in 36 (66.7%) patients, while SPECT/CT localized 4 glands in 19 patients (35.2%). Although the number of US-detectable PGs was not associated with success rate, it showed a significant negative correlation with surgical time (rs = -0.459, P = 0.002).

Conclusion: US detected 4 glands in 66% of SHPT patients with a sensitivity of 90% for localization. Ectopic position and small size were the most common reasons for the failure to detect PG on US. Complete preoperative echo localization might shorten operating time.

Keywords: Parathyroid glands; Secondary hyperparathyroidism; Ultrasonography.

Fig. 1. Flowchart of screening for eligible cases. SHPT, secondary hyperparathyroidism; MIBI, technetium 99m-sestamibi; SPECT, single-photon emission CT.

Fig. 2. Parathyroid hyperplasia was shown on ultrasound in transversal (A) and longitudinal (B) views. Typical characteristics include homogenous hypoechogenicity, oval or multilobulated shape, and peripheral vascularity.

Fig. 3. Ultrasound in transverse views of an ESRD patient (A: right upper parathyroid gland [RUP], B: right lower parathyroid gland [RLP], C: left upper parathyroid gland [LUP], and D: left lower parathyroid gland [LLP]) showing secondary parathyroid hyperplasia compared with intraoperative findings (E).

J, internal jugular vein; C, carotid artery; NG, nodular goiter; T, trachea; TH, thymus.

Fig. 4. Causes of ultrasound-missed parathyroid hyperplasia. (A) Ectopic bilateral lower parathyroid glands in the thymus. (B) The left upper parathyroid gland (LUP) was misdiagnosed as part of the thyroid nodule (NG), compared to the intraoperative findings (right). (C) The right upper parathyroid gland (RUP) overlapped with the right lower one (RLP), compared to the intraoperative finding (right). C, carotid artery; NG, nodular goiter; TH, thymus.