Urinary calcium and phosphorus excretion and their relationship in calcium-containing urinary stone formers

Abstract

Calcium-containing upper urinary stone formers (group SF-A, n = 116) and normal controls (group Normals, n = 10) were examined for urinary calcium (Ca) and phosphorus (P) excretion (mg/mg creatinine) on usual diet, on Ca-restricted diet and in basal period. As a result, urinary Ca and P excretion decreased significantly both in group SF-A and in normal controls, as the dietary intake was reduced. As compared with normal controls, group SF-A exhibited significant elevation in urinary Ca excretion and showed a slight, though not significant increase, in urinary P excretion. A significant positive correlation between urinary Ca and P excretion was observed in either mode of diet in group SF-A, while no correlation was seen in normal controls. To examine the legitimacy of the result above obtained, another 40 Ca-containing upper urinary stone formers (group SF-B) were studied on usual diet. Thus, better correlation was obtained between urinary Ca and P excretion. In conclusion, urinary Ca and P excretion will be strongly influenced by their dietary intake. Stone formers excrete more Ca and P than normal controls. Finally, a tendency was noted that stone formers excreted the more Ca, the more P.