[Peroral calcium administration test with free diet in idiopathic calcium nephrolithiasis--possibilities and limits]

Seventeen patients who recurrently formed idiopathic calcium kidney stones (SF) and 25 age- and sex-matched healthy blood donors (H) were challenged by an oral calcium load (1 g) after an overnight fast. Their usual diet was not changed before the test. Urine samples were taken before, 2 1/2, and 4 h after the calcium load. A blood sample was drawn 3 3/4 h after calcium loading. Before and 2 1/2 h after calcium dosage urinary measurements of calcium, magnesium, phosphate, oxalate, uric acid, and creatinine did not reveal any differences between SF and H. According to the calciuria after 4 h SF were separated in normocalciurics (NCSF) and hypercalciurics (HCSF). Nine-tenths of the NCSF had higher serum ionic calcium levels than H after calcium load (P less than 0.001), whereas HCSF were not different from H. Serum phosphate in SF was lower than in H (P less than 0.001). Carboxy-terminal parathormone, measured in 3 NCSF and 2 HCSF, was normal. Depending on the calciuria or calcemia 4 h after an oral calcium load, 16 of 17 SF showed a metabolic abnormality (hypercalcemia or hypercalciuria). It is concluded that intestinal calcium absorption in SF might be increased to variable rates.