Causes of discordant or negative ultrasound of parathyroid glands in treatment naïve patients with primary hyperparathyroidism

Objectives

To describe causes of discordant or negative parathyroid ultrasound and to assess factors influencing them.

Materials and methods

Retrospective review of patients who underwent parathyroidectomy between 2000 and 2012 was done. Imaging findings were compared with operative findings and pathology to identify discrepant (n = 60; 32 negative, 28 incorrect) parathyroid ultrasounds.

Results

Fifty (83.3%) patients had parathyroid adenoma, of which 10 (16.6%) were ectopic and three were double adenomas; 8 (13.3%) had multigland hyperplasia and two had parathyroid carcinoma. Discrepant reports were due to incorrect localisation in 8 (13.3%); difficulty in differentiating thyroid from parathyroid lesion in 12 (20%); large and small size in two and three patients, respectively; overcall in 5 (8.3%) and satisfaction of search in 7 (11.7%) patients. There was significant correlation between presence of multi-nodular goitre and incorrect reports (χ² = 4.112, p = 0.04). Experience of ultrasound operators performing initial and second look ultrasound was significantly different (p < 0.0001). Second look ultrasound was concordant with surgical findings in 39(65%) patients; 21 (66%) patients with initially negative ultrasound and four out of five extra-mediastinal ectopic lesions. Ten patients with negative initial ultrasound had elongated parathyroid lesion. Scintigraphy was concordant in 44 (73.3%) patients and nine were ectopic.

Conclusion

Second look ultrasound performed by experienced operator for negative or discordant initial ultrasound of parathyroid is a useful strategy which will improve the accuracy of parathyroid ultrasound. Being able to differentiate thyroid from parathyroid lesion is a factor which will influence performance of parathyroid ultrasound.