7 yr history of recurrent kidney stones. Parathyroid scintigraphy dual-phase 99mTc-Sestamibi + 99mTc-pertechnetate

Case presentation:

• Female.
• 30 y.o.
• 7 year history of recurrent kidney stones.
• Hypercalcemia(11.4 mg/dL). -IncreasedserumPTH (199 pg/mL).
• Diagnosticwork-up forsuspectedprimary hyperparathyroidism(performedin a peripheralhospital):

1.  Normal neck US examination.
2. No parathyroid scintigraphy performed.
3. Measurement of bone mineral density (DEXA): i. vertebral BMD 0.8959 gr/cm2  (T score -1.2; Z score –1.1. ii. femoral  BMD 0.656 gr/cm2 (T score -1.7; Z score –1.7).
4. 24-hr urinary calcium: 388 mg (100-300).
5. No Vitamin D deficiency.

• December 2008, Bilateral neck exploration:

1. No evidence of abnormal parathyroid glands.
2. Thymectomy performed because of suspected intra-thymic localization.
3. Histology: normal thymic tissue.

• February 2009 (persistent hyperparathyroidism): Small nodule in thymic region (6×8 mm) detected on neck.

Teaching points:

• The use of a pin-hole collimator in the neck increases image resolution.
• The chest is best evaluated with a parallel-hole collimator either as a planar image or using SPECT (better topographic correlation).
• SPECT(and especially SPECT/CT) is most helpful in evaluation of the mediastinumas the possible site of ectopic parathyroid glands.