Hypercalcemia due to hard water used for home hemodialysis.

We have described two patients from the same rural community in Georgia who had hypercalcemia during home hemodialysis. In the first patient the diagnosis was not considered until after the patient complained of the poor taste of her home tap water and of the white residue it left on her cooking utensils; other causes of hypercalcemia had been ruled out. The diagnosis was confirmed when samples of tap water that had passed through the in-line deionizer showed low to high calcium concentrations. Calcium concentrations were high after the deionizer filters had been in place for some time but within the acceptable guidelines for the type of filters used. The second patient, seen shortly after the first, had also received dialysis with hard water and also had hypercalcemia despite the use of an in-line deionizer. These cases suggest that dialysis-induced hypercalcemia can occur during home hemodialysis despite seemingly adequate pretreatment of the water source.