Background. Metastatic lung calcification (MLC) is an important complication in long-term dialysis patients, causing respiratory disturbance. We used single photon emission computed tomography (SPECT) in lung (L-SPECT) to detect the distribution of MLC. Methods. L-SPECT with 99mtechnetium hydroxymethylene-diphosphonate was performed in 59 patients who had been on maintenance dialysis for more than 5 years. The accumulation count ratios were calculated from counts in the upper lung field (UL), lower lung field (LL), basal lung field along the diaphragm (BASE), and the cardiac pool (POOL). Distribution patterns of radionuclide were classified into four groups. Pulmonary function tests and blood examinations were performed. Results. The median values for UL/POOL, LL/POOL, and BASE/POOL were 1.71, 1.85, and 2.21, respectively. On the SPECT images, 28 patients had positive lung accumulation, versus 7 on the planar images. Patterns and frequency were: group I (none or slight accumulation), 32.2%; group II (accumulation only in the basal lung field), 33.8%; group III (accumulation in the whole lower lung or above), 18.6%; and group IV (diffuse accumulation extending to the whole lung field), 15.2%. Intact osteocalcin level was 6.3 ± 5.3 ng/ml in groups III + IV (large group) vs 94.2 ± 184.3 in groups I + II (small group) (P < 0.01). The number of patients with declining diffusion capacity was 20.0% in the large group, vs 5.1% in the small group. All patients in group IV had an intact parathyroid hormone (i-PTH) level of under 65 pg/ml. Conclusions. L-SPECT is very useful for the early detection of MLC, the extension of which may reduce diffusion capacity. Diffuse calcification over the whole lung is considered to be related to a low-turnover bone state concomitant with low PTH level.
ASJC Scopus subject areas
- Physiology (medical)