US imaging and color Doppler in patients undergoing inhibitory therapy with calcitriol for secondary hyperparathyroidism

The aim of this study was to evaluate the changes in volume, structure, and flow pattern of parathyroid glands in uremic patients with secondary hyperparathyroidism treated with long-term intravenous calcitriol (CTL) therapy. Ultrasonography was used to follow-up volume changes occurring in 18 enlarged glands in 11 patients during an 18-month period; in 6 of these cases, 11 glands were followed-up also with color-Doppler to monitor variations in flow pattern. Vascularization was classified using three grades: grade 0=no color signal; grade I=vessels covering less than 50% of glandular cross-sectional area; grade II=vascular signals covering more than 50% of glandular cross-sectional area. No significant changes in volume were demonstrated during the 18 months of follow-up. On the contrary, significant decrease in flow was observed with almost complete disappearance of color-Doppler signals. This finding related well with the observed decrease in parathormone blood levels. Lack of volume changes during medical therapy demonstrates the inability of US alone to monitor the effect of this treatment on the parathyroid glands. Conversely, the observed intraglandular flow reduction indicates the possibility to use color Doppler to monitor the effects of CLT in uremic hemodialyzed patients with secondary hyperparathyroidism. This imaging procedure can be proposed for follow-up of the response of the parathyroid glands to therapy.