The effect of citrate on calcium oxalate (CaOx) crystal growth was studied in a system in which series of samples containing [45Ca]calcium chloride were brought to different levels of supersaturation with various concentrations of oxalate. The crystallization was assessed by measuring the amount of isotope remaining in solution 30 min after the addition of CaOx seed crystals to samples containing citrate in concentrations corresponding to those in final urine. The experiments were carried out both in pure salt solutions and in solutions with dialysed urine. Increased concentrations of citrate resulted in a reduced crystallization of CaOx in both the presence and absence of dialysed urine, but with the lowest rate of crystallization in the samples containing urine. The increased concentration of 45Ca remaining in solution reflected a reduced crystallization, which could possibly be explained both by a reduced supersaturation and by an increased inhibition of CaOx crystal growth. The direct effects of citrate on CaOx crystal growth were assessed by calculating the ion-activity product of CaOx (APCaOx) at corresponding degrees of crystallization. The APCaOx recorded at a 30% reduction of the amount of isotope in solution increased with increasing concentrations of citrate between 1.0 and 1.5 mmol/l samples both with and without dialysed urine. These findings indicate that citrate has a weak direct inhibitory effect on CaOx crystal growth, which adds to the reduced growth rate brought about by urinary macromolecules and a decreased supersaturation.

The biochemical risk situation in calcium oxalate stone formers can be summarized by quotient 2 or 3.

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The aim of this one-year investigation of school accidents was to determine the incidence and severity and to calculate the proportion of school accident cases in relation to all accident cases and to estimate their medical care consumption. All patients were interviewed. The degree of severity was evaluated according to the Abbreviated Injury Scale (AIS). Case-histories and X-ray reports were examined. School accidents constituted five per cent of all accidents in the whole population (including grown ups). In the age group 7-19 years 30% of all accidents were school accidents. One fourth was relatively severe. Our estimations assume that school accidents constitute 5-10% of the total consumption of medical care in the age group. In conclusion, school accidents constitute an important group with regard to incidence and severity. Preventive measures should be targeted towards activities during sports hours and breaks.

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