Pulmonary calcification in hemodialyzed patients detected by technetium-99m diphosphonate scanning

Metastatic pulmonary calcification, a well-known complication in patients with chronic disease, has been demonstrated postmortem in patients with a negative chest X-ray. Recently, scintigrams with bone-seeking radionuclides have been used to detect such subclinical pulmonary calcium deposits. We describe 23 patients on maintenance hemodialysis with no evidence of pulmonary calcification on chest X-ray who were prospectively studied by lung scanning with a bone-seeking radionuclide and pulmonary function testing. Of the 23 patients, 14 (61%) had a positive technetium-99m diphosphonate (99mTc-DP) scan (group 1). These patients were on dialysis 38 +/- 5 months compared with 12 +/- 4 months in 9 patients with a negative scan (group 2) (P less than 0.01). Age, sex, blood pressure, hematocrit, serum calcium, phosphorous, bicarbonate, magnesium, and calcium X phosphorus product, as well as parathyroid hormone level did not differ between the two groups. Of 10 group-1 patients tested, 7 had abnormal pulmonary diffusion capacity compared with non in 5 group-2 patients tested (P = 0.014). Histologic examination of the lung in 1 group-1 patients who expired revealed calcification (amorphous on X-ray diffraction), whereas none was found in 1 group-2 patients autopsied. These observations suggest that in patients on maintenance hemodialysis, pulmonary scanning with 99mTc-DP is a sensitive method for detecting pulmonary metastatic calcification, which may be associated with an abnormality in pulmonary diffusion capacity.