The usefulness of single photon emission computerized tomography with pinhole collimator (P-SPECT) in preoperative localization of hyperfunctioning parathyroid glands in patients with secondary hyperparathyroidism.

PURPOSE: In this study the usefulness of parathyroid scintigraphy was evaluated in a group of patients affected by secondary hyperparathyroidism, combining the conventional double-tracer subtraction planar scintigraphy with pinhole-SPECT (P-SPECT) acquisition and comparing the scintigraphic data with those obtained by ultrasonography.

MATERIALS AND METHODS: Twenty-four patients with secondary hyperparathyroidism were enrolled, 19 with chronic renal failure on haemodialysis and 5 with renal transplant. All patients underwent parathyroidectomy because of their unresponsiveness to medical therapy and/or severe osteodystrophy. Histology ascertained a single adenoma each in 3 patients and 61 hyperplastic glands in the remaining 21 cases. Before surgery, all patients were submitted to high resolution ultrasonography and afterwards to double-tracer subtraction planar parathyroid scintigraphy ((99m)Tc-pertechnetate/(99m)Tc-tetrofosmin) followed by neck P-SPECT acquisition.

RESULTS: P-SPECT was true positive in all 24 patients, while both planar and ultrasonography were false negative in one case. Globally, P-SPECT identified 60/64 hyperfunctioning parathyroid glands, planar 47/64 and ultrasonography 45/64. P-SPECT sensitivity (93.7%) was significantly higher than both planar (73.4%; p<0.001) and ultrasonography (70.3%; p< 0.0005). The difference was also significant (p<0.05) when P-SPECT sensitivity was compared with that obtained combining planar scintigraphy and ultrasonography (84.4%). Moreover, P-SPECT defined the exact number of hyperplastic glands in 85.7% of positive patients, while planar in 60% and ultrasonography in 45%. Only 4 hyperplastic glands were false negative at P-SPECT showing a maximum diameter of 10 mm and a weight ranging from 480 to 500 mg. These glands were also false negative at both planar scintigraphy and ultrasonography which missed further 13 and 15 hyperfunctioning glands, respectively, all detected by P-SPECT. Globally, the latter procedure gave the correct preoperative localization of hyperfunctioning parathyroid glands in 87.5%, planar in 62.5% and ultrasonography in 50%. None of the three procedures had false positive

CONCLUSIONS: The data of the present study seem to indicate that P-SPECT is a reliable diagnostic method in preoperative localization of hyperfunctioning parathyroid glands in patients with secondary hyperparathyroidism. This procedure identified a significantly higher number of hyperplastic glands than both double-tracer subtraction planar parathyroid scintigraphy and ultrasonography in our cases, thus proving a more useful guide for the surgeon. Given its low false negative rate, a wider use of P-SPECT is suggested in the preoperative management of patients with secondary hyperparathyroidism undergoing either a first operation of parathyroidectomy or a second operation for recurrence.