Non-localizing Parathyroid Adenomas: Radiologic Error or True Entity

Abstract

Objectives:

Investigate radiographic assessment of non-localizing parathyroid adenomas (NLPA). Our goal was to determine whether non-localization is a result of radiologic interpretive error, or truly representative of non-visible parathyroid adenoma.

Methods:

We performed a retrospective chart review of 364 patients who underwent parathyroidectomy over a 5-year period. Thirty patients who were identified as having NLPA on pre-operative imaging were included. All available patient images were re-reviewed by two senior radiologists. Both readers were blinded to surgical outcomes and adenoma location on the first read of the imaging studies. Surgical outcomes were then revealed and the imaging was re-reviewed. The two reader’s results were subsequently compared for inter-reader reliability using Cohen’s kappa test.

Results:

All 30 patients with NLPA had pre-operative 99mTc sestamibi imaging available and 18 also had an ultrasound performed. Adenomas were identified intra-operatively and removed in all cases. Twenty-nine of the thirty (97%) 99mTc sestamibi studies were scored by the two readers as either negative or equivocal. There was excellent inter-observer agreement between the readers, with a kappa value of 0.706. For the ultrasound studies, however, the two readers’ inter-observer agreement was only fair, with a kappa value of 0.351.

Conclusions:

The inter-reader agreement in our series supports the conclusion that, for a sub-population of patients with parathyroid adenoma, pre-operative imaging will be truly negative/non-localizing.