Bone scintigraphy in uremic pulmonary calcification

The value of Tc-99m HEDP bone scintigraphy as a means of detecting uremic pulmonary calcification was studied in 30 chronic dialysis patients. A high incidence of currently recognized predisposing factors for metastatic calcification was found and calcification was recorded at other sites. Scintigraphy was performed after reducing background activity by hemodialysis to levels found in normals. From chest images and chest-to-spine activity ratios, evidence of pulmonary calcification could be obtained in only one patient, and subsequent histologic examination revealed extensive calcification. High chest-to-spine activity ratios suggested increased pulmonary radionuclide uptake in several other patients, but these findings were not conclusive. These results indicate that uremic pulmonary calcification--which, according to autopsy studies, develops in about 60-75% of dialysis patients--cannot be detected with bone-seeking radiopharmaceuticals, unless the calcification is severe. This is probably due to the unusual crystalline and chemical composition of uremic pulmonary calcification.