Usefulness of bone scintigraphic classification and quantitative evaluation of bone mineralization with X-CT and SPECT in renal osteodystrophy

1. Bone scintigraphy with Tc-99m-MDP was performed on 52 patients with chronic renal failure. These bone scintigrams were classified into 4 groups, each of which was correlated to laboratory data and quantitative data of bone mineralization. Group I (32 patients) showed high accumulation of Tc-99m-MDP in the bone. High level of Alk-Pase and c-PTH, low BMC/BW, low EMI number and high radionuclide activity ratio (RN ratio) were observed. Group II (9 patients) demonstrated nuclear bone images with high background activity. RN ratio was slightly higher than the normal. Group III (11 patients) showed extraosseous accumulation of Tc-99m-MDP in the lung, kidney or soft tissues. One patient belonged to Group I. High level of Ca x P product and slightly high RN ratio were observed. In both Group II and III, BMC/BW and EMI number were normal. Group IV (one patient) showed normal skeletal activity on bone scintigram. The mean duration of hemodialysis was the longest in Group I. Our scintigraphic classification is convenient and might contribute an understanding of patho-physiological bone changes in such patients. 2. Subtotal parathyroidectomy (S-PTX) was employed in 18 of 52 patients on chronic renal failure with secondary hyperparathyroidism. These patients were studied before and after S-PTX using 6 different procedures; conventional radiography, microdensitometry, bone mineral analysis, measurement of EMI number with X-CT (frontal bone), bone scintigraphy, and RN ratio (frontal bone/brain) with SPECT. On the bone scan, the diffuse increased activity in the calvarium became less prominent after S-PTX in all 18 patients. We devised a new method to quantify the bone changes revealed by the bone scan; the RN ratio with SPECT. The ratio decreased markedly after surgery. This method seems to be most useful for detecting dynamic bone changes sensitively and quantitatively. (author)