[Calcium concentrations in the urine of recurrent stone-formers and their controls (author's transl)]

Over a period of 4--6 weeks the urinary concentrations of (total calcium, ionized calcium, creatinine and osmolarity in recurrent stone-formers and healthy controls were measured in morning, midday and evening urine samples. The mean urinary concentrations of the (total) calcium were in both groups the same. However, 31% of the stone-formers and only 18% of the controls showed a mean calcium concentration > 5 mmol/l. The ionized calcium, on the contrary, was significantly higher in the stone-formers than in the controls. The lower urinary osmolarity of the recurrent stone-formers led to significantly higher Ca/osmolarity and Ca2+/osmolarity ratios; analogously, the quotient Ca2+/creatinine was also significantly raised in stone-formers.