Ultrasonic parathyroid localisation in previously operated patients.

Sixty-two patients with hyperparathyroidism and failed prior neck surgery were examined by ultrasound before reoperation to localise abnormally enlarged glands. If mediastinal lesions are excluded, a total of 57 glands greater than 5 mm in size were removed from 48 patients. Ultrasound demonstrated only 18 of these for a true positive rate of 32%. There were 39/57 (68%) false negatives. In addition, there were 16 false positives. In our experience, the detection rate of ultrasound for enlarged parathyroid glands in patients with failed surgery is significantly less than that reported in previously unoperated patients (73%), or in the limited number of reported cases of patients with previous operations (75%). Our high false negative rate is probably partially due to the large number of posteriorly located small glands which cannot be adequately visualised by ultrasound. Nevertheless, because of its non-invasive nature, low cost and ready availability, ultrasound should be utilised as an initial screening procedure in patients with failed previous surgery.